Neurophilosophy of Sensation
I : The
Organs of Perception.
Smell : the nose feels the air.
Taste : tongue and water.
Touch : bending & stretching from top to toe.
Audition : the pressures of air.
Sight : the eye as the space of photons.
Naked perception : stimuli & preliminary codation.
Natural perception : space, time, integration & projection.
The Sensuous Cortex :
The sensory areas : perception & its cortical processing.
The association areas : to the final integration of perception.
The angular gyrus : symbol tools.
The prefrontal cortex & empirico-formal concepts.
12. Sensations in epistemology, ethics and esthetics.
The argument of illusion.
To understand how audition happens,
musicology -based on the cycle of communication, and rooted in critical
epistemology & process ontology- integrates the neurology of sensation, in
particular audition. Of course, besides hearing, visual & kinesthetic
objects of sense also play a role (the visual is intimately part of Opera
and the more subtle kinesthetic input is related to the sensatons related
structure of the locus of the actual musical production, causing
temperature changes). Of course, when
considering music, the two prime senses involved are audition and sight
In particular, the receiver is at hand, more precisely the symbol-receptor
and integrator. Especially nowadays, when "inner hearing" is complemented
by the possibility of sampled playback, is the sender also involved, and
composition itself makes use hearing (playback) and sight (score).
When the neurological properties of hearing & seeing are understood, one
may wonder how this information is processed at the level of the sensitive
surfaces of the sense organs in question. Moreover, what happens when this
informatie travels to the brain and gets connected with thalamic &
post-thalamic (neocortical) neurological processes. This may help to
explain the difference between naked perception and natural perception,
between perception & sensation, as well as the fact of interpretation of
sensate objects by different human brains. These also point to the
phenomenon of filtering or the play of foreground (accentuation) &
The composer aware of this play of illusion may take this into
consideration when writing & producing music, anticipating interpretation
and making use of the art of auditive suggestion ... This begs the
question of the possibility of a "total artwork", i.e. one involving all
the senses. This may seem farfetched, especially when considering smell &
taste (cf. a musical score indicating what kind of odor and food one
should partake of during audition !).
Also consult my
I : The
Organs of Perception.
"Each of us believes himself to live directly within the
world that surrounds him, to sense its objects and events precisely, to live in
real and current time. I assert that these are perceptual illusions, for each of
us confronts the world from a brain linked to what is 'out there' by a few
million fragile sensory nerve fibres. These are our only information channels,
our lifelines to reality. These sensory nerve fibres are not high-fidelity
recorders, for they accentuate certain stimulus features, neglect others. The
central neuron is a story-teller with regard to the afferent nerve fibres ; and
he is never completely trustworthy, allowing distortions of quality and measure,
within a stained but isomorphic spatial relation between 'outside' and 'inside'.
Sensation is an abstraction, not a replication, of the real world."
Mountcastle, 1975, cited in
Popper & Eccles,
the preliminary codification
The neurophilosophy of the
transport of information from the PNS (Peripheral Nervous System) to the CNS
(Central Nervous System), studies
the afferent, sensoric, incoming impulses from the five senses, crucial to
distinguish perception from sensation.
The efficient neurological cause of perception is
called "transduction" ("to lead across"). This is the logic by which a receptor
cell, exposed to an environmental stimulus, causes an electrical response. On a
deeper level, the overall functioning of the brain is thus underpinned by
complex flows of electric charge (from the Greek "electron" or "amber"), which,
together with magnetism, shapes the fundamental interaction known as
electromagnetism (next to universal gravity and the subatomic strong & weak
forces). Electromagnetism implies the simultaneity of electrical &
The magnetic field is caused by the electric current or motion of electric
The electromagnetic field is the space which exerts a force on particles
possessing electric charge, in turn affected by these particles and their
motion. All sensate information gathered by the senses is transducted into
electromagnatic impulses transported to the CNS.
Traditionally, "sensation" is defined as the faculty through which the external world is
perceived. Hence, the sensory system is two-tiered
: on the one hand perception, the raw, naked immediacy of the receptor
organs for smell, taste, touch, audition & sight, the "doors of perception"
the periphery of the olfactory, gustative, soma-esthetic (or somato-sensory),
visual & auditory systems of the CNS. On the other hand sensation, the
end result of an array of central neural systems committed to process the coded
form of the impulse perceived by the receptors, like the secondary & tertiary
sensory areas, the spatial association area
situated in the posterior parietal cortex (of both hemispheres), the
angular gyrus in the inferior parietal lobe, sitting at the juncture of the
tactile, visual & auditory areas, the limbic system (for emotional coloring)
and the Ascending Reticular Activation System in the brainstem for the general
arousal-level of the CNS.
|primary to tertiary areas, gyri, the
The transmission of afferent impulses is never
direct, but by synaptic relays, changing the massage into a "code". In every
neuronal relay station, this coded impulse is modified. Although each sense has
its primary receiving area laid out as a cortical "map" (cf. the Brodmann
areas), the neuronal relays from the PNS to the CNS cause the preliminary
"codification" of the raw impulse hitting the reception surface of nose, tongue,
skin, ears and/or eyes. So when the impulses in some sensory pathway reach the
primary sensory areas in the CNS, preliminary codification has already taken
place (cf. Kant's distinction between experience, "Empfindung" versus
appearance, or "Erscheinung").
"In general it can be stated that the intensity of the
stimulus is encoded as frequency of discharge of impulses."
Popper & Eccles,
from perception to sensation
Mental states are either based on sensation or are non-sensational. In the
latter case they are mental objects. Indeed, the cognitive system (cognition)
only processes two types of objects : sensate objects & mental objects. The
latter can be classified as volitional, affective, cognitive and sentient
(consciousness). The sensate objects define the body, mental objects define the
Sensations have a
clear bodily location and possess "raw feels" or qualia,
defined by the five-tiered sensory input of the five physical organs of sense
(smell, taste, touch, audition and sight). More or less spatially defined, sensations
are always the experience of a conscious subject. Without this conscious
experience, sensations are not. So they are a higher-order kind of empirical
The distinction between sensation and
perception is important. Sensations occur to a subject of experience, and
manifest as nose-consciousness (smelling), tongue-consciousness
(tasting), skin-consciousness (touching),
ear-consciousness (hearing), eye-consciousness (seeing) & the concert of these. They represent the
final, "constructive" result of a process starting with naked, "unconstructed" perception.
Perceptions are raw & simple, sensation are always processed & complex.
Sensations happen to
an empirical ego (largely processed by the prefrontal lobes of the neocortex,
the so-called "fourth brain" next to the reptilian, mammalian and human brains)
with a unique perspective on the ongoing, sensational & non-sensational stream
of functional differences or "energies" within consciousness.
Perception is three-fold. The root of perception is the impulse affecting the
receptor. Next, the afferent relay to the CNS is coded, finally projecting the
coded impulse in the primary sensory
area. Because these perceptional data are
introduced through sensory pathways to which consciousness has normally no
direct access, perception is, paradoxically, non-sensational. To clarify this
idea, the neurophilosophy of the primary, secondary & ternary sensory areas will be
mental states have no distinct, outer events associated with them.
These mental states, also emerging without one being conscious of
them, may be classified as :
• quasi-perceptional states :
hallucinating, dreaming, imagining, trance-visioning ;
• emotions, feelings : the
complete range from utter disgust to sublime bliss, from violence to peace ;
• conative states : wishing,
wanting, intending, trying, acting ;
• cognitions : thinking,
reasoning, knowing, conceiving, understanding, intuiting.
In a general way, mental states are defined as
volitional, affective, cognitive and sentient. The so-called
Mind/Body-problem is investigated in an separate paper :
A Philosophy of the Mind and Its Brain, 2009.
Smell : the nose feels the air.
The earliest organism abided in chemical substances
signaling food, poison or sex. In humans, externally located neuronal cell
bodies are concentrated within the nose. These nasal-located neurons, like those
of other, more ancient creatures, analyze the pheromonal, olfactory and chemical
nature of the environment for data concerning food, sex, the weather and the
like. Over the course of evolution, only two groups of primal sensory cells formed
like-minded cells : the olfactory lobe and the optic lobe. With the
expansion and axonal-dendritic interconnection of these lobes the modern brain
the olfactory bulbs & optic vesicles of the neural tube
Bear, Connors &
figure 7.10 p.182.
We do not smell with the nose, but with a small, thin sheet of cells high up in
the nasal cavity. This olfactory epithelium, about 10 cm², has three main cell
types : (a) olfactory receptor cells, or neurons with axons of their own
penetrating into the CNS, (b) supporting cells, similar to glia, helping to
produce mucus and (c) basal cells which are the source of new receptor cells.
Indeed, the receptor cells continually grow, die and regenerate in a cycle
lasting ca. 4 to 8 weeks. The olfactory epithelium and the retina of the eye are
both literal extensions of the brain.
The olfactory system gave rise to the
evolution of the primitive amygdala and rudimentary hippocampus ca. 500 million
years ago. Because odors are inherently slow stimuli, rapid timing of action
potentials is unnecessary to encode the timing of odors. Rather, temporal
coding, based on the timing of spikes, is supposed to encode the quality of
odors, and transduce the chemical stimulus into an electric charge. Temporal patterns of spiking would then be the logic behind the olfactory
In lower mammals, olfaction is
the dominant sensory input, but in humans it became subordinate to sight,
hearing and somaesthesis.
Humans are relatively weak smellers. A smell is detected when about 10 trillion molecules
of one of the ca. 30.000 or so available odor molecules enter the nose and
stimulate its 50 million primary sensory receptor cells. Humans are able to detect and remember ca. 10.000
odors. Each of these cells express only one of the 1000 types of odorant
receptor genes. Dogs have more than 100 times more receptors in each square
centimeter of the olfactory epithelium, which may be over 170 cm².
Olfactory receptor neurons send axons into two olfactory bulbs, full of neural
circuits with complex dendritic arrangements, reciprocal synapses and high
levels of various neurotransmitters. Olfactory information is modified by
inhibitory & excitatory interactions within the structures of the bulbs and
between them. Neurons in the bulbs are also subject to modulation from systems
of axons descending from higher areas in the brain. The output axons of the
olfactory bulbs run through the olfactory tracts and have a complex
distribution, the principal termination being in the piriform cortex (or
olfactory cortex), the primary sensory area of olfaction, thus making various
direct connections to many structures of the limbic system, the "nose brain".
From there, the axons go to the thalamus on to the neocortex, were conscious
recognition of smell occurs in the orbito-frontal cortex right behind the eyes.
This anatomical feature makes olfaction unique, for all other sensory systems
first pass through the thalamus before projecting into the neocortex. Only
olfactory connects with a primary sensory area directly related to temporal lobe
structures & the limbic system.
The limbic system has been referred to as the "nose brain". The afferent axons
stimulate this system directly, without the
thalamus or "universal gateway" of the CNS. Indeed, the spinothalamic pathway is
the major route by which afferents (registering for example pain or temperature)
ascent to the neocortex. The thalamus is thus the gate through which information
carried by sensoric axons enters the CNS. Here, these afferents are
pre-processed to branch out to the relevant cortical areas & the limbic system.
The unicity of olfaction is clear. Like all sensory systems, it makes use of a
method of preliminary codation to relay information to the CNS, but unlike any
other system, it branches out in the limbic system before being pre-processed in
the thalamus and relayed to the neocortex and its primary sensory area in the
Olfaction directly connects with emotion and the latter evolved from feeding,
fighting, fleeing and sex. Smell is the first sense, and some neurologist claim
the brain as a whole evolved from it. Our first contact with the outer world is
therefore based on odors.
02. Taste : tongue & water.
The olfactory system is related to eating and assists the
gustatory system. Flavor can only be detected if both nose & tongue are used
together. Although completely independent of the taste buds localized
along the tongue, both system may have started out as one chemoreceptive system
becoming distinct over the course of evolution. In reptiles and many other
animals, an auxiliary olfactory organ is located within the roof of the mouth.
But, in this case too, the two systems are separate. Indeed, some food, although
smelling good, may taste terrible and have no nutritive value. The taste test
allowed for additional differentiation, although some stuff smells & tastes great
while still being poisonous.
Both smell & taste are chemical senses using a variety of transduction
mechanisms to recognize the large amount of chemicals encountered. For an
omnivore, a sensitive and versatile system of taste was essential to survive.
Some taste preferences, like sweetness, is innate, but experience strongly
modifies these instincts. The body has the capacity to recognize a deficiency
and adjust this by causing cravings for particular food. We recognize four basic
tastes : sweetness, saltiness, sourness & bitterness.
Although we mainly taste with our tongue, the palate, pharynx and epiglottis
also participate, as well as the olfactory system. Scattered about the surface
of the tongue are small projections called papillae (or bumps), shaped like
ridges, pimples or mushrooms. Each papilla has hundreds of taste buds, composed
of ca. 50 - 150 taste receptor cells, only about 1% of the tongue epithelium.
Taste buds have also basal cells surrounding the receptors and a set of
gustatory afferent axons. A person has ca. 2000 - 5000 taste buds, while
exceptional people have as few as 500 or as many as 20.000.
As is the case for the other sensory receptors, papillae tend to be sensitive to
only one basic taste and only at some critical concentrations just above
threshold is a stimulus evoked. This does not mean sweetness is only tasted with
the tip of the tongue. The tongue map implies certain areas of the tongue are
more sensitive to the basic tastes than are other regions, while most of the
tongue is sensitive to all basic tastes. Single receptors show small differences
in response, and subtle distinctions are made in the brain. When a taste
receptor cell is stimulated by an appropriate chemical, its membrane potential
changes, either depolarizing or hyperpolarizing. This voltage shift, or receptor
potential, causes the cell to fire action potentials.
The neuronal coding of taste is not based on specific receptor types, axons and
neurons. Taste buds are broadly tuned to stimuli and this is the case all the
way into the CNS. Receptor cell inputs converge onto afferent axons, and each
receptor synapses into a primary taste axon also receiving input from several
other receptors. One axon may combine taste data from several papillae. This is
called population coding, used throughout the sensory and motor systems of the
brain. This seems to be an architecture already at work at the level of the
action potential of the neuron, making a combined decision based on all
stimulating (yes) and inhibiting (no) nerve impulses influencing it
(cf. the "democratic neuron").
The main flow of taste data is from the taste buds to the afferent gustatory
axons, into the brain stem (medulla), up to the thalamus and finally to the
neocortex. In the brain stem, the axons synapse with the gustatory nucleus and
diverge from there. The thalamus sends axons to the primary gustatory area, the
cortical area in the anterior insula of the cortex (in the parietal lobe).
In a general sense, smell & taste are not used in musical perception. Even in
Wagner's "Gesamtkunstwerk", no specific odors or tastes are integrated. Given
the importance of smell, putting olfactory preferences in a score, is possible
and even practically feasible. Taste, being too transient, seems however
farfetched (and is intimately related to smell).
03. Touch : bending &
from top to toe.
The experience of touch starts at the skin. Most sensory
receptors in the somatic sensory system, are mechanoreceptors, sensitive to
physical distortions such as bending or stretching, enabling the body to feel, to
ache & to chill (in the context of this paper, the term "somatic sensation" is
avoided). Present throughout the body,
they monitor all contact with the skin as well as pressure in the heart & blood
vessels, stretching of the digestive system, urinary bladder and force against
the teeth. The axons branches characterizing each mechanoreceptor have
mechano-sensitive ion channels, not well understood.
As the largest organ of the body, the skin is richly innervated by axons part of
the vast network of peripheral nerves. In the visceral system, primary afferent axons bring information
from the somatic sensory receptors up the spinal cord, only synapsing in the
dorsal root ganglia (or cuneate nucleus at the base of the head). Information
about touch or vibration of the skin takes a route to the CNS entirely distinct
from pain and temperature stimuli. Indeed, some of the axons terminating in the
root ganglia start at the skin of the big toe. At this point, the information is
still represented ipsilaterally (right side body, right dorsal nuclei). But
axons from these cells arch and decussate. From this point onwards, the somatic
system of one side is concerned with sensoric data deriving from the other side
of the body.
After only one synapse, the
afferent impulse travels to the thalamus & the cerebral cortex. At each of two
relays (root ganglia & thalamus), the opportunity for an inhibitory action is
given, sharpening the neuronal signals by eliminating the weaker excitatory
stimuli. By this inhibition, a precise localization of touch stimuli becomes
Somaesthetic or somatosensory processing occurs in
the cerebral cortex, namely the parietal lobe. The primary somatosensory cortex
occupies an exposed cortical strip, the postcentral gyrus. The somatotopy of
this gyrus has been called a homunculus (or "little man"), a mapping of
the body's surface sensations.
The temperature of the space where music is performed impacts our sense of
touch, causing bending & stretching (of the skin). Like smell, this is very
subtle, and works in the background. In terms of musical performance it cannot
be said to be of primary importance, but should not be neglected. Indeed, also
musical instruments are influenced by temperature. All extreme temperatures need
to be avoided.
The spatial characteristics or ambience of music is not part of the score, but
depends on where the music is represents is produced and the actual distribution of vocalists
& instruments during playback. This ambience impacts our experience of space and
this it intimately related to hearing. Indeed, whereas the
ear is the receptor organ for fine air pressure transduction, the physical
body as a whole acts as a soundboard. In this way touch is an integral part
of the musical experience.
04. Audition : the
pressure of air.
Sounds are audible variations in air pressure caused by moving
air molecules producing sound waves. A source of sounds causes these variations
to disperse in all directions. When an object moves away, air is made less dense (rarefied).
Many sounds produce periodic variations in air pressure. The frequency of sound
is the number of compressed patches of air passing by our ears each second. One
cycle is the distance between two successive patches. Sound frequency is
expressed in Hertz, or the number of cycles per second. The auditory system
responds to pressure waves over the range of 20 - 20.000 Hz, decreasing with age
& exposure to noise of the high-frequency end (a low organ tone is about 20 Hz,
while a high note on a piccolo is about 10.000 Hz). Intensity of sound is
difference in pressure between compressed patches of air, and determines the
loudness we perceive. The higher the intensity, the louder the sound. The
intensity range is remarkable, for the loudest sound leaving our ears undamaged
is about a trillion times greater than the intensity of the faintest sound heard.
The ear has three main divisions. The structures from the funnel (pinna) to the
eardrum is called the "outer ear". The tympanic membrane and the ossicles
constitute the middle ear and what lies behind the oval window is the inner ear.
These structures of the auditory pathway play the following roles :
pinna (or funnel) : helps
collecting and localizing sounds ;
auditory canal : extending
ca.2.5cm inside the skull ending at the tympanic membrane ;
tympanic membrane : the eardrum
• ossicles ("little bones") : a
series of three bones or transferring movements of the tympanic membrane into
movements of a second membrane covering a whole in the bone of the skull called
the oval window ;
("snail") : behind the
oval window, this is a fluid-filled space containing the apparatus transforming
physical motion of the oval window membrane into neuronal responses. This
involves a frequency analysis of the patterns of sound waves and their
conversion into the electromagnetic discharges of neurons. The auditory receptors converge
mechanical energy into a change in membrane polarization (cf. the organ of
Corti, consisting of hair cells, the rods of Corti and various supporting
Once the inner ear generates the neural response to sound,
the signal is transferred to and processed in nuclei in the brainstem, and sent
to a relay in the thalamus, finally projecting to the primary auditory cortex in
the temporal lobe (Heschl's gyrus). Both audition & sight start with sensory
receptors connecting to early integration stages (retina for sight and brain
stem for audition), relay to the thalamus and then to the sensory cortex.
Nevertheless, given there are more synapses at nuclei intermediate between
the sensory organ and the cortex, the auditory pathway appears more complex than
the visual pathway. However, the cells and synapses of the auditory system in
the brain stem are analogous to the interactions in the layers of the retina. All
ascending (afferent) auditory pathways converge onto the inferior colliculus of
the midbrain. The right cochlea projects mostly to the left primary auditory
area, and vice versa for the left cochlea. So just as taste & smell work
together, so do sight & sound. Touch is clearly an all-encompassing sense,
gerally diffuse, but when called for very specific.
Neurons processing sound information are timing devices. They are designed to
preserve & analyze very rapid neural signals encoding small but meaningful
variation in sound signals. A trained pianist can distinguish between two tones
of 1000 Hz and 1001 Hz, or the detection of a difference of only 1 μsec in the
wavelengths ! A single action potential lasts about 1000 times longer. The
detection of a sound source in the horizontal plane with a precision of 2° is
possible, demanding the discrimination of 11 μsec difference between the time it
takes a sound to reach their two ears. Many auditory neurons in the brain stem
have an architecture & physiology optimized for speed and electrical conduction.
This extremely precise localization is also necessary to report position and movement of
the head (the vestibular system). Indeed, both the auditory and vestibular
systems use hair cells to transduce movements.
Music depends on hearing. And the six attributes of sound, namely pitch,
dynamics, rhythm, counterpoint (horizontal), harmony (vertical) & color, depend
upon the physicalm properties of the sound wave : frequency, amplitude, duration
and form. Concerning sound waves, they are air waves stimulating the tympanic
membrane, the bony system, the oval membrane, the liquid of the inner ear and
the complex receiving mechanism of the afferent nerves, all the way up to the
thalamus and from there to the sensory areas of the neocortex, transforming the
perceived impulse into conscious sensation.
Sight : the eye as the space of photons.
The majority of the light hitting the surface of the Earth comes from the Sun,
and this is only a fraction of what our star disperses into outer space in all
directions. Light, electricity & magnetism are all electromagnetic
radiation. The electric and magnetic fields oscillate at right angles to each
other, while the combined wave moves in a direction perpendicular to both of
these two field oscillations.
Light, of constant speed in empty space, may be conceived as moving packages of energy
called photons. Paradoxically, a photon is a particle of electromagnetic radiation
with no mass. Light
is both particle-like & wave-like. Whether light moves like a wave or as a particle depends on
it is observed (cf. the importance of the experimental setup in the two-slit
In a digital camera, both aspects of light are addressed. The lens of the
camera refracts (bends & focuses) incoming waves of light. These waves
are made to hit a charge-coupled
device (CCD). This is a light-sensitive integrated circuit storing & displaying
image-data. Each picture element (pixel) is converted into an electrical charge
related, by intensity, to a color in the color spectrum. Subatomically, this
intensity is measured by light photons kicking electrons out of the silicon
contained in the bombarded surface.
These electrons are finally detected by electronics interpreting the number of electrons
released and their position of release from the silicon to create an image.
The length of a light wave λ is the distance between successive peaks or
troughs, its frequency ν is the number of waves per second,
and its amplitude is the difference between peak and trough, related to the
intensity or brightness of a wave relative to other light waves of the same
wavelength. Light features a simple relation between its
speed (c), wavelength (λ) and frequency (ν), namely
(1) ν = c/λ. Since λ, the wavelength in Ångstroms (1 Ångstrom = 10-10 meter), bottoms the fraction, frequency is inversely proportional to
the wavelength. Light with a smaller wavelength has a higher (larger) frequency
and vice versa.
White light is made of different colors or wavelengths. When
passed through a prism, it spreads out in
different colors (cf. the rainbow of the visible spectrum). This phenomenon
shows how all possible wavelengths become manifest. "Hot" colors such as
red or orange consist of light with a longer wavelength, and these have less
energy than "cool" colors such as blue or violet.
||4000 - 4600
In physics, a quantum (plural : quanta) is an indivisible
entity of energy. For instance, the photon, being the unit of light, is a "light
quantum". In empty space, a photon moves at a constant speed, has no rest
and no charge. Einstein (1879 - 1955) found the relationship between the energy
of light E and
its frequency ν to be : (2) E = h × ν, h being Planck's constant,
or 6.626 × 10-34 J·sec, used in the quantization of energy. The
energy of electromagnetic radiation is proportional to its frequency. Emitted at
high frequency (or short wavelengths) it has the highest energy. (1) & (2) give
E = h.c/λ, with c = 299.800 km/s (the speed of light in empty space).
Light rays travel in straight lines until interacting with the atoms & molecules
of the atmosphere and objects. These interactions include reflection, absorption
Reflection is the bouncing of light rays off a surface. Most light
we see is reflected off objects. Striking a mirror perpendicularly will reflect
light 180° back upon itself, at 45° a reflection of 90° occurs, etc.
is the transfer of light energy to a particle or a surface of molecules. Black
surfaces absorb the energy of all visible wavelengths, while some compounds
absorb a limited range of them and reflect the remaining. "Violet" absorbs long
wavelengths, but reflect a range of short ones centered on 430 nm (4300 Å), perceived as
Refraction is the bending of light rays traveling from one transparant
medium to another. Striking a surface at an angle will bend the light toward a
line perpendicular to it. This bending occurs because the speed of light differs
in the two media, passing through air more rapidly than through water (cf.
greater the difference between the speed of light in the two media, the greater
the angle of refraction.
the visual system
A large part of the cerebral cortex is involved with analyzing the visual world
captured as the electromagnetic radiation visible to our eyes. In the
electromagnetic spectrum, ranging from Gamma rays to AC circuits, the visible
spectrum of rainbow colors lies between wavelengths of 400 & 800 nm (1 nanometer = 10-9 meter = 10 Ångstroms),
in other words, light visible to our eyes has wavelengths between 4000 - 8000 Ångstroms.
The structures involved in all steps of the visual pathways are complex. The eye
is an organ specialized for the detection, localization and analysis of light.
The gross anatomy of the eye is as follows :
pupil : the opening allowing
light to enter the eye and reach the retina ;
: surrounds the pupil, pigmented to provide the color of the eyes. It contains
two muscles varying
the size of the pupil (one makes it smaller when it contracts, the other larger)
: pupil & iris are
covered by a glassy transparant external surface, lacking blood vessels and
nourished by the fluid behind it, the aqueous humor. It is continuous with the
sclera, the "white of the eye", forming the tough wall of the eyeballs ;
extraocular muscles : inserted
into the sclera, they move the eyeball in the bony orbits of the skull ;
back from the inside of the eyelids & attached to the sclera ;
retina : a sheet of closely
packed visual receptors (ca. 107 cones and 108 rods) at
the back of the eyeball, on which an image is formed ;
• optic nerve : carries axons from
the retina and exits the eye at the back, passes through the orbit and reaches
the brain at its base, near the pituitary gland.
The conversion of light energy into neuronal activity happens
in the retina. The basic flow of light in the retina is from the photoreceptors to bipolar
cells to ganglion cells. The only light-sensitive cells in the retina are the
photoreceptors, while all other cells are influenced by light via direct or
indirect synaptic interactions with these. The ganglion cells are the only
source of output from the retina. They alone form action potentials. The actual
conversion of electromagnetic radiation into neural signals occurs in the 125
million photoreceptors at the back of the retina. They convert light energy into
changes in membrane potential, using biochemical cascade. The retina could be
seen as an integral part of the brain !
influence of light/dark contrast with identical gray
Each cell has four regions :
an outer segment, an inner segment, a cell body and a synaptic terminal.
Light-sensitive photopigments absorb light and trigger changes in the membrane
potential of the photoreceptor. Rod photoreceptors have a long, cylindrical
outer segment, while cone photoreceptors have a shorter segment. Rods are 1000
times more sensitive to light, while there are three types of cones, each
containing a different pigment, making them sensitive to different wavelenghts
of light. Only the cones are responsible for our ability to see color.
The axons of the ca. million ganglion cells travel in the optic nerve. About 10%
of this retinofugal projection courses from each eye to the midbrain (the
superior colliculus), while most of them innervate the thalamus, and from there
go to the primary visual cortex or striate cortex in the occipital lobe (the
nonthalamic targets of the optic tract involves about 150.000 neurons). The
optic nerves exit the left and right eyes and travel through the fatty tissues
behind the eyes and pass through holes in the floor of the skull. These nerves
from both eyes form the optic chiasm, which lies at the base of the brain,
anterior to where the pituitary gland dangles down. In this chiasm, optic
nerve fibers cross from one side to the other (decussation). Hence, the
left visual field is viewed by the right hemisphere and the right visual field
is viewed by the left hemisphere. The actual viewing happens in the primary visual
From the striate cortex, a ventral stream of information projects into the inferior temporal cortex, where the highest integration of
visual function & analysis occurs. This is the end station of a system of recognition of
specific and particular shapes and objects of interest, both cognitively as
well as emotionally, for interconnected with the amygdala, hippocampus, limbic
system and the autonomous nervous system.
Composers often speak of the "paper value" of a score, meaning the way it looks.
Sometimes the mere visual absence or presence of some score element pops out,
suggesting ways to esthetically alter the score and so the corresponding music
(for example, two woodwinds ending a 16th note apart may be "corrected" to end
together). In the XXth century, composers experimented with new kinds of scores,
heavily depending on special visual marks and suggestions, introducing
stochastic factors depending on mere visual stimuli (special score elements). To
write & read a score, the visual system is important, although this can also be
replaced by touch (cf. braille music).
During an actual performance (score playback), the activities of the
instrumentalists, the vocalists & the conductor offer a wide spectrum of
interesting psychological & emotional information, but this has hardly anything
to do with music (although in some cases, the movements of the conductor may
assist a better understanding of the auditive data). However, in the grand art
of Opera, the visual element can be said to be as important as the vocal
& instrumental parts (as in Richard Wagner's "Gesamtkunstwerk"). Indeed, the
interaction between what happens on stage and the motifs played by the orchestra
is decisive to grasp the intent of the composer regarding the action at hand.
In a general way, we may conclude music may relate to all senses except taste,
although smell has not yet been really integrated (but offers, given the
possibility of the timed release of pheromones) interesting new perspectives ...
But of the five senses, hearing, sight (in Opera) & touch (as ambience) are
06. Naked perception : stimuli
& preliminary codation.
"If the doors of
perception were cleansed,
every thing will appear to man as it is, infinite.
For man has closed himself up,
till he sees all things thru' narrow chinks of his cavern."
Blake, 1790/2, The Marriage of Heaven and Hell.
The receptor organs of the sensory system are fed by impulses based on chemical
substances, collisions & frictions, air pressures and electromagnetic radiation.
These impulses are the first cause of perception, nothing else. Stimuli are the
direct, external changes caused by a narrow band of material objects on the
surface of the receptor organs of the sensory system.
Molecules alter the chemistry of nose & tongue. The mechanics of stretching &
bending triggers somatosensoric responses. Each second, compressed patches of
air pass by our ears. Variations in electromagnetic energy stimulates the
retina. Take away these stimuli or disable the receptor organs, and perception
is either absent, partial or impossible. The receptor organs are the "doors of
Without perception, no interpretation of perception and hence no sensation. To be
physically in touch with our environment, evolution provided five doors.
Although more may be available (cf. imagination & mind), sense perception is the
primary fact of physical experience shared by all humans at birth. It is
nominal and the cause of sensate objects.
scientific, liberal or specialist, all our education is predominantly verbal and
therefore fails to accomplish what it is supposed to do. Instead of transforming
children into fully developed adults, it turns out students of the natural
sciences who are completely unaware of Nature as the primary fact of
experience, it inflicts upon the world students of the Humanities who know
nothing of humanity, their own or anyone else's."
1957, p.59, my italics.
We first smell, taste, touch, hear and/or see (perceive) and then consciously
experience odor, taste, feels, sound & light (sense). Throughout the sensory
system population coding is used, implementing a threshold for combined
action-potentials. This procedure enables broad responses.
Between the moment the receptor organ changes (stimulus - perception) and the actual
conscious sensation (response - sensation), two levels of interpretation exist : automatic &
interpretation from receptor organ to thalamus :
evolutionary, biological software integrated in the hardware of the
brain, involving transduction, coded relays & the reception by thalamus, it
involves no conscious interpretation ;
processed interpretation from thalamus, primary sensory
cortex to prefrontal cortex :
evolutionary software plus userware (volitional & processed), able to change
software & influence hardware, calling for the secondary sensory cortex, the
association areas, the angular gyrus & the prefrontal cortex. This involves
In each receptor organ, a particular
transduction is operational from, on the one hand, chemical (smell, taste,
touch), mechanical (touch, audition) or electromagnetic energy (sight) to, on
the other hand, encoded sequences of electric voltages running through neurons
and their axons and dendrites.
transduction of chemical stimuli (odorants) by temporal coding (the timing of
transduction of chemical stimuli by membrane potential changes, either
depolarizing or hyperpolarizing (voltage shift) ;
transduction of mechanical and chemical stimuli by membrane potential changes &
mechanoreceptors (with mechano-sensitive ion channels ?) ;
transduction of mechanical energy by a change in membrane polarization ;
transduction of electromagnetic radiation by a change in membrane polarization.
The axons of the olfactory bulbs run through the
olfactory tracts and project directly into the olfactory cortex.
This happens without passing through the thalamus first, as is the case
for taste (gustatory afferent axons), touch (somatosensoric axons),
audition (auditory nerve) & sight (optic nerves), projecting into the
neocortex by thalamic relay.
Smell is an exceptional sense, able to swiftly trigger massive limbic
responses. Indeed, its primary sensory cortex belongs to the primitive
cortex, which is part of the limbic brain, the nose brain. Olfactory
afferent input and its projection into the primitive regions of the
cortex (piriform cortex) is nonthalamic, making smell unique
among the senses. This cortex has three layers, the neocortex
six. From this old piriform cortex, many connections to
many structures in the limbic brain are made. Many parallel
pathways mediate the olfactory functions, such as odor discrimination,
emotions, motivation & behaviours from reproduction, feeding to
imprinting and memorizing.
The role between odorants and emotional memory (hippocampus) is
pertinent. The olfactory system is the outer organ of the play of
emotional tensions between inhibiting and exciting. It heralds danger,
sexual activity & a feeling of well-being (cf. the role of pheromonal
communication between animals). Conscious smelling is mediated by
pathways between the medial dorsal nucleus of the thalamus and the
stem and cerebellum removed
Bear, Connors & Paradiso, 2001, p.211.
Both transduction & the axonal relay (by way of
synapses), as well as the thalamic relay, are important "automatic"
interpretations (innate software), each altering the code, upgrading it from (1) receptor
(from receptor neurons to thalamus) to (2) integrator (thalamus). These
are the first level of the "innate software", given at birth, and the
result of millions of years of evolution. The second level of this
"evolutionary software" involves the integration of the relayed data and
its projection on the neocortex by the thalamus (cf. infra).
It took millions of years for receptor neurons to be able to receive &
transduce. This "automatic" level of perception is called "naked"
because it touches, so must we think, the absolute (or "Ding-an-sich").
Reality-as-such & ideality-as-such, the Real-Ideal, is onefold and
crucial in logic, epistemology, ethics, esthetics & ontology. Naked
perception is the truth-core of realism. The latter is
methodological ("as if"), not ontological. This means it does not
operate as ground, foundation or hypokeimenon of thought,
knowledge, goodness & beauty (cf.
Clearings, 2006). By way of method, we
accept certain physical stimuli out there cause changes in
the receptor organs, effectuating a chain of events relayed, in a coded
format, to the thalamus.
Insofar as stimuli cause material changes, transduction causes neuronal
information to be relayed to the thalamus.
07. Natural perception :
time, space, integration & projection.
To reach the neocortex and become conscious
sensation, all afferent sensory inputs directly (taste, touch, audition,
sight) or indirectly (smell) enter the thalamus. The thalamus is the
gate, integrator and translator of various inputs processed into
a form readable by the neocortex. As a projector, the thalamus relays
selectively to various parts of the neocortex, and one thalamic point
may reach more than one area of the cerebral cortex.
At the level of the thalamus, reptilian & mammalian (innate) software takes over.
Before entry into the neocortex, this "inner
room" or "storeroom" (of a Greek or Roman house)
receives the neuronal messages of the five senses. This sensory information is
spatio-temporalized, integrated and finally projected into the primary
sensory cortex, while the intensity of the flow to and fro the neocortex is monitored and if
necessary inhibited. Recent studies suggest signals are also relayed
from the thalamus to deeper layers of the brain at the same time ...
Through this inhibition, the thalamus rules the flow of sensory (and other
neuronal) information to the cerebral (neo)cortex and
acts as a highly state-dependent "reducing valve" or central sensory
gate (filter). This is done by the reticular nucleus, a sheet of
acetylcholine inhibiting neurons, covering the whole of the dorsal
thalamus. This sheet contains nerve cells gathering information from
dendrites draping the outer surface of the thalamus, sampling the
activity between thalamus and neocortex. Cortical excitatory states
descend and excite the reticular nucleus, blocking perception. Brain
stem excitatory states ascend and inhibit the nucleus, allowing more
sensate messages to flow to through the thalamus into the neocortex.
Higher mammals have a larger pulvinar ("cushion"), the back of the
thalamus. In humans, it occupies one quarter of the thalamus and is the
essential thalamic counterpart of the sensate association cortex
covering the back of the neocortex. Functionally, it seems to make the
initial contribution to the process of automatically grasping & holding
items in our visual & auditory space or salience. This allows them to
become of meaningful interest. So the thalamus also computes our
initial level of attention. And there is more : the medial dorsal
nucleus assists frontal scenario's, the anterior nucleus brings in
sensual gratification, the intralaminar nuclei stimulate, the lateral
genicular nucleus "sees", and the reticular nucleus is a shield (Austin,
1998, pp.263 - 274). What an incredible storehouse !
This "automatic" level of perception is called "natural" because our
brain shares it with all higher mammals. In humans, the thalamus acts
not only as a receptor and an integrator-projector, but also as the
initiator of a series of higher cortical functions. It is the second
level of the "innate software" we inherited from our mineral, vegetal &
animal ancestors ...
The neocortex is never directly informed about the afferent data
provided by both naked & natural perception. Conscious sensation is a
posthalamic process. This is important to realize. When we sensate an
object, it is already filtered, or, mutatis mutandis, our
unconscious perception is vaster than our conscious sensation ...
II : The Sensuous Cortex.
The cerebrum (measuring about 11 m²) is divided into
four lobes, situated underneath the corresponding bone of the skull :
• the frontal bone of the
forehead covers the frontal lobe ;
• the temporal bone (temple)
defines the temporal lobe ;
• the parietal bone (caudal of
the central sulcus making the posterior border of the frontal lobe) covers
the parietal lobe ;
• caudal to the parietal
lobe, under the occipital bone lies the occipital lobe.
the cerebral lobes
Bear, Connors & Paradiso, 2001, p.207.
Gray cortical matter is found in the cerebral neocortex, a thin layered sheet of
ca. 209 neurons
lying just underneath the surface of the cerebrum.
|number of neurons
|number of cortical neurons
|surface of neocortex
|connections per neuron
(*) Koch, C : Biophysics of
Computation, Oxford University Press - New York, 1999, p.87.
In the human, the neocortex is the set of neurons of the cerebrum where sensations,
voluntary movement, learning, speech & cognition converge. Here consciousness &
the sense of "I-ness" are mediated. It shares several common features with all
vertebrate animals :
• neurons are arranged in
layers or sheet, mostly parallel to the surface (the human neocortex has 6
• the layer closest to the
surface is separated from the rest by a zone lacking neurons ;
• at least one cell layer
contains pyramidal cells with large, apical dendrites extending upwards
& forming multiple branches ;
• the cerebral neocortex has a
cytoarchitecture distinguishing it from the basal telencephalon. The latter
neuronal structures directly underneath the neocortex. The subcortical
networks of this "deep" telencephalon interconnect the neocortex with the
diencephalon (differentiates into thalamus & hypothalamus), the limbic
Computing all higher order operations is the "nominal"
mode of working of the human cerebrum or neocortex and its specific, bi-modal approach : two
hemispheres processing one integrated cerebral activity from two different
angles. Abstract thoughts can be thoroughly mediated after the axonal bridge between
both, the corpus callosum has been completed (cf. Piaget's
"formal-operatoric phase" after the age of 10). is horizontal & vertical.
Contrary to the reptilian, mammalian and all other cortical brains on Earth, the neocortex of
Homo sapiens sapiens is exceptional in size, wiring & function. Of all mammals,
humans have the most "uncommitted cortex" at birth (Penfield, 1975),
i.e. fewer neurons with, in their hardware, instinctual patterns
built-in. This implies
the human brain is made for organic neuroplasticity (the more difficult a task, the
more cells process it) and also has great ability to learn and
individualize. Hence, it is ready to acquire "cultural software", the result of
socialization, communication and culture. This turns each neocortex into a
unique network, defined by unique patterns and hence individuality in
The bi-modality of the human
unique human hemispheral specialization
Joseph, 1993, p.44
Horizontally, there is the joint project of the two cerebral
hemispheres : cerebral activity is called to be an integration of a duality.
This is accepting the difference while opening up as many neuronal alleys
between the hemispheres (cf. the "concordia discors" of thought
Vertically, the neocortex (or upper telencephalon) and the basal
telencephalon perform different tasks (note : in left handed people, the
directions should be reversed). The basal telencephalon is part of the limbic
system. It is essential in the relay of information down from and up to the
neocortex and adds "emotional color" to what comes in and goes out.
Especially the amygdala play a crucial role in this, while the
association of memory & emotion is noteworthy.
hemisphere - neocortex :
higher order verbal operations ;
hemisphere - basal telencephalon : emotion/word associations, digital
hemisphere - neocortex : the higher order visuospatial operations ;
hemisphere - basal telencephalon : emotion/imaginal sensations,
Primary & secondary sensory area :
perception & its cortical processing.
The stretching & bending human body (touch) is constantly
afloat in a pool of chemicals (smell & taste), air pressures (hearing) and
electromagnetic radiation (sight). The chemical senses (smell & taste) produce
odors & tastes, the mechanical senses (touch & audition) feels & sounds and the visual
sense transforms radiation into pictures of the
world around & outside us. Through them, an experience of the immediate
environment becomes possible.
The relay from stimulus to perception seems rather "automatic". Although the
inputs of the sensory organs are transduced, then relayed to the thalamus to be
finally projected into the neocortex, what enters the cerebrum at any given
moment is very likely the coded effect of the state-altering stimuli received.
Perception is based on the S-R (Stimulus - Response) format, whereby the same
stimulus, in ceteris paribus, causes the same response. In neo-Darwinian
logic, these forms are the outcome of the countless "trials & errors" of
evolution, eliminating inadequate paths and keeping the fittest.
Smell is the first sense, bringing in an overall sense of the immediate
environment. Together with taste it also helps to provide good food & a proper
mate. Like touch, these are senses at work in the immediate context. Hearing is
crucial when light is dim and distance needs to be reckoned (mediate context).
Sight brings in a panoramic perspective (general context), and informs about
details when used nearby. For all of these, an imperative (innate) algorithm or
software was implemented and "somehow" stored in the cells. This is like
software permanently encoded on the hardware, reacting in tune with biological,
and electromagnetic laws.
The research of
Kaas (1995) et al. suggest the primordial
neocortex (existing to some degree in all living species) consists of
types of cortex, called the "primary sensory cortex", the "secondary sensory
cortex" & the "motor cortex". These receive input from the thalamic nuclei
relaying data from the basal telencephalon & the cerebellum and send outputs
to motor control neurons in the brain stem & spinal cord.
• primary sensory
cortex : receives as first signals from the ascending sensory pathways,
relayed by the thalamus and project these into the secondary sensory areas ;
• secondary sensory
cortex : very interconnected with the primary sensory areas, they as it were
assist computation ;
• motor areas
: concerned with the control of voluntary movement.
The association areas : the final integration of perception.
The cortex proceeds by shaping a three stepped "neuronal
sensation ladder" :
area : processing the thalamic projection and the decodation of its
In the human brain, even after assigning
primary sensory, secondary sensory, primary motor & secondary motor areas to the neocortex, a
considerable amount of bark, particularly in the frontal & temporal lobes,
remains : the association areas.
association areas : process the recent,
human development of the primate cortex, namely the
ability to symbolize & interpret in terms of unobservable mental states.
Conscious sensation computes here, for sensations are interpreted
In these association areas
of the human neocortex,
sophisticated processing mediates higher order functions & operators. These areas contain neurons
able to "associate" or "gather together" neural states from
various parts of the brain, not only the neocortex. Information from the sensory areas, memory systems
and the diencephalon (emotional states) is put together and integrated
in order to optimalize the possibilities of the nervous system and execute,
process, compute, mediate & enhance a conscious sensation of the world.
Some of these areas are interconnected with the amygdala, hippocampus, limbic
system and the autonomous nervous system. Hence, at this point the more or less
"automatic" responses (in various degrees) are replaced by "learned", "acquired"
userware, implemented as a result of conscious (sentient) activity.
the functional areas of the human cerebrum
Bear, Connors & Paradiso, 2001,
pp.208 & 642.
Four "association areas" have been discovered :
association area : inferior temporal cortex : highest integration of
visual function & analysis - end station of a system of visual recognition of
specific and particular shapes and objects of interest, both cognitively as
well as emotionally - interconnected with the amygdala, hippocampus, limbic
system (olfactory cortex) and the autonomous nervous system ;
association area : posterior parietal cortex : highest integration of
analysis and integration of higher-order visual, auditory and somaesthetic
(touch & body position) information - three dimensional image of the
body in space - distinction between what is at arm's length (bodily sense)
and what is further away (the world) - some neurons motivate and guide hand
movements, including the grasping of objects within grasping distance ;
association area : angular gyrus,
at the junction of the posterior-superior temporal and the
: area of
the highest integration of all sensory input, with rich interconnections with
all other association areas - processes abstract thought and their relation
to words (Wernicke & Broca in the left hemisphere) - conceptual
comparisons, ordering of opposites, naming of objects, higher logical
association area (also : attention association area) : prefrontal cortex,
frontal lobes : receives fibers from all
sensory systems (vision, hearing, touch, taste, smell), but has few
connections with the primary sensory areas - very interconnected with the
limbic system (emotional responses), verbal and spatial association area
(conceptual thought and egocentric spatiality) - coordinates highly complex
movements and is the "seat of the will" for all goal-oriented
behaviors, actions and intentions - able to focus on important tasks through
redundancy (screening out superfluous input) - planning, imagining, deciding
and attention regulation throughout the cerebrum are computed here, but a
complete functional picture is far from clear. This has been called the
"fourth brain" (next to the reptilian, mammalian and the rest of the
neocortex or "human brain").
The association areas allow us to "experience" in a conscious
way, and integrate all higher order functions, such as cognition, affection,
volition and consciousness. In the formal & critical modes of thought (cf.
Wisdom, 2007), circular consciousness circumambulates a sense of
personal identity. At best, this empirical ego is present & attentive of itself
and its environment in every cogitation, affection and/or volition. This is the
"subject of experience" confronted with an "objective" fact and its
extra-mentality (resulting from causes seemingly outside the perimeter of the
Although both subject and object of experience seem unconstructed, the neuronal
processing enabling their manifestation betrays a modular sequencing. Insofar as
the sensory system is concerned, the association areas bring in a wide range of
inputs, from emotional coloration to verbal, spatial, volitional, imaginal
regulations. This brings to the fore the constructed, fabricated, mediated, derived,
conditioned, assembled, mapped nature of sensation. Sensation comes about thanks
to userware, culturally acquired software. To express sensation,
cognition, affection, volition & consciousness, a wide range of neuronal areas
are addressed. Indeed, at the higher levels of the nervous system, neuronal
activity is secured by neurons arranged in colonies or modules, making neuronal
parsimony highly unlikely.
Eccles (1981, p.361) speaks of "neuronal prodigality", linking the processing of
consciousness not with psychoneural identity (as the author, he is an
A Philosophy of the Mind and Its Brain, 2009), but with
"reading out from the multitude of active centres at the highest level of brain
activity, namely the liaison areas of the dominant cerebral hemisphere. The
self-conscious mind selects from these centres according to attention, and from
moment to moment integrates its selection to give unity even to the most
transient experiences. Furthermore the self-conscious mind acts upon these
neural centres modifying the dynamic spatiotemporal patterns of the neural
events. Thus we propose that the self-conscious mind exercises a superior
interpretative and controlling role upon the neuronal events. A key component of
the hypothesis is that the unity of conscious experience is provided by the
self-conscious mind and not by the neuronal machinery of the liaison areas of
the cerebral hemisphere." (p.362).
Sensation, the final integration of perception, involves interpretation and
construction. Sensation is the result of an active modulation of the perceived
inputs. Hence, conscious sensation can not do away or eliminate these
interpretations, for consciousness has no direct experience of perceptions,
but only of sensations.
An interesting neuronal pathology called "blindsight" makes this very clear.
Normally, primary & secondary visual areas are so integrated we are unable
to isolate the particular role played by each in our day-to-day visual
processing. But when the primary visual cortex is lost, the secondary cortex
reveals itself as blindsight.
When patients lack the function of the primary visual cortex on one side of the
cerebrum, then their consciousness (mediated by the prefrontal cortex) seems
"blind" to events taking place in their visual field on the opposite side. So
far nothing special. But this is not the same kind of absolute visual
loss as when an eye is gone or the optic nerve is severed. This blindness is
relative. For if a moving stimulus is offered to their blind field, then
patients point at the target even though unable to consciously see it. In other
words, forced to guess about whether a stimulus is present in their blind field,
some observers do better than chance. Their secondary visual enables the ability
to respond appropriately to visual inputs while lacking the consciousness of
having seen them.
This proves unconscious perception, given the senses, the relays & thalamic
projections are intact, is always happening ! Moreover, what is perceived at
this level is far richer than sensation. The latter is always a filtered outcome
! This also explains why some psychedelic drugs allow us to "sensate" more.
Indeed, they reduce the activity of the valve, allowing the neocortex to be
"flooded" with information normally staying below conscious threshold. This
filter was put in place for evolutionary reasons, for survival without filtering
is dangerous, to say the least. Even today, experiments show the abuse of
psychedelica leads to loss of motivation and a-social behavior, both crucial
when dealing with a hostile environment.
The hierarchy at work in the sensory system makes the distinction between
perception & sensation pertinent. Is it possible music manipulates the
activity of the perceptive valve ? Can music transport us "in another
world" and open vistas normal conscious states do not ? Does it accommodate a
more conscious awareness of the limbic systems and its strong emotions ?
The angular gyrus : symbol tools.
In the human cerebrum, the angular gyrus and hemispheric
specialization are quite unique. Hominoids and other non-human mammals lack an
angular gyrus and their artistic, tool-making & symbolic capacities are limited
to hammering rock & throwing or manipulating leaves, sticks & twigs (Fedigan,
The angular gyrus, at the junction of the posterior-superior temporal and the
occipital-parietal lobes, is crucial in all constructional tasks, in the control
of sequential hand movements, in the manipulation of external objects and
internal impressions, but also in naming (adding a label or putting
impressions in "a box").
Joseph (1982, 2000) evidenced how the evolution of this area allowed
humans to engage in complex creative, symbolic and artistic activities. Devoid
of this gyrus, humans develop apraxia, the inability to perform tasks involving
interrelated steps and sequences.
Besides naming, this gyrus is also involved in word finding and grammatical
speech organization, "and is in part an extension of and
links Wernicke's with Broca's areas" (Joseph,
This is the cortical area
of the highest neuronal integration of the perceptions of the five senses. Rich
in interconnections with
all other association areas, the angular gyrus processes abstract thought
(the "form" of identities & relationships) and their relation
to words in terms of speech & the coordination of the making of correct
acoustic sounds or phonemes (cf. Wernicke & Broca in the left hemisphere).
Conceptual comparisons, ordering of opposites, naming of objects, higher logical
operations etc. are mediated by this area. As the verbal association area, this
gyrus integrates sensation, naming and organizing as well as the production of
the spoken word. In humans, sensation is used to categorize and talk.
For Joseph, the angular gyrus evolved over the course of the last
two millions years and this in parallel with the evolution of handedness and
tool technology. Given the relationships between right handedness, the left
hemisphere and language, he conjectures speech production also gradually arose
over the same period. This explains the explosion of tool-making by the
Cro-Magnon, who possessed an angular gyrus and large frontal lobes.
For the Neanderthals, tools were use-specific. Handedness was not yet that
developed (in manipulative tasks, they still helped themselves with their mouth).
Vocalization was probably in its infancy.
"... it is with the evolution of
the Cro-Magnon, the angular gyrus and expansions in the frontal lobe which
provided the neurological foundations for tool design and construction, the
ability to sew and even wear clothes, and the capacity to create art, and
pictorial language in the form of drawing, painting, sculpting and engraving. It
is the evolution of these tissues which enabled human beings to not only create
visual symbols but to talk about them and create verbal and visual symbols in
the form of written language and religious imagery."
During human evolution, hemispheric specialization was probably a
response to the unique demands made by language, speech and tool construction,
in short, infusing material media with conscious meaning, enabling a lasting
"sediment" or "glyph". Symbolization is glyph-making insofar as the sediment or
material carrier or calculator is lasting enough to bridge to a new generation of
listeners & talkers.
Making & manipulating tools,
identifying certain sounds with sensate objects (naming), as
well as grammatical order are all processed in this unique cortical area.
Talking & listening are the most powerful tool of the Homo sapiens sapiens (cf. the nearness of the auditory cortex).
highest neural processor of language & speech (directly related to the areas of
Wernicke & Broca), is also crucial to all tools related to the artistic
11. The prefrontal cortex & empirico-formal concepts.
sensory areas / frontal lobe schematics
The exceptional evolution of the human frontal lobes
materialized language (symbolization), tool
technology & art. Branched to a wide array of modules, they are the "senior executive" of
the brain (Passingham, 1993,
Fuster, 1989) and are primary in regard to all
aspects of imagination, creativity, speech, language (via Broca's area) and
symbolic thinking. In the frontal lobes, the executive brain, the coordination and regulation of
attention, individuality, memory and cortical activity is at hand. Intellectual, creative,
artistic, symbolic and cognitive processes get executed. They subserve the
expression of melodic-emotional and vocabulary-rich grammatical (well-formed) speech.
Consciousness and the sense of "I-ness" or personal identity (cf. the first
person perspective of reality-for-me) also compute in these frontal lobes. Here
naming turns into concept-formation.
Consciousness superimposing probability fields
does not violate the physical conservation laws (for m = 0), but, ex
co-determines the final momentum of matter & information and this hand in hand
with the deterministic evolution of the physically determined vector,
either as material states (particles, forces) or material glyphs (material
states infused with meaning). Each nondetermined choice needs many sensitive &
state-dependent states to influence, alter, modify, etc. the most likely outcome
(the automatic result). In a constructive sense, this calls for many
nondetermined choices to alter the determined result so all involved may benefit
from it. Sensation, the end result of the sensory system, is therefore not
automatic, but very user-specific, implying an "internal process". The latter
includes consciousness as well as its executive cortical modules.
At this level, conscious sensation, as the experience of a sensate object by the
subject, is processed. This sensation is based on what the secondary sensory
areas, motor areas, angular gyrus & other areas relay (and not so much on
input from the
primary sensory areas). Hence, sensation is a highly fabricated phenomenon, sharing
characteristics with reptilian and mammalian emotional responses to certain
perceptions, i.e. adding interest (brain stem and thalamic valve), emotional coloring
(limbic) and, in the case of the human, symbolic interpretation (verbal association area) before
conscious experience (prefrontal lobes).
Already in the thalamus, state-sensitive flow-reducing processes are at work,
allowing the system to cancel the "automatic" response of the
afferent pathways (from receptor organs to thalamus). These highly
complex mechanisms, sensitive to a gentle push, opening & closing major neuronal
pathways at a moment's notice, are in number present in the neocortex. Each of
these association areas accommodate a particular cortical software, dealing with
a modular representation of a set of problem-solving information-items. By
constantly interacting (cf. the ongoing, interdependent cortical process) and relaying
the prefrontal cortex, they allow for a higher order computation of a hierarchy
of operations, in casu, of sensory inputs. There too mental objects
(volitions, affects, thoughts & sentient awareness) are generated.
Nominal (conscious) sensation (S) of Homo normalis is the neural product of two
vectors : perception (P) & interpretation (internal process, I). The conceptual mind cannot experience an
object of sensation without interpretation (identifying, naming,
associating, etc.). This is normal and nominal in the so-called "waking" state. Maybe
consciousness is to be "expanded" or "altered" to include what is today only
"unconscious" ? Can the liaison brain be more than the frontal lobe of the
dominant cortical hemisphere ? Artistic & spiritual models affirm.
Next to the congenital "innate" codation from receptor organs to thalamus (in accord
with the S-R model), highly
state-dependent cortical networks or modules invite free will (and
volition) to alter ongoing procedures (based on the brain's actual & past functioning).
Directly influencing the probability-fields of wide populations of neurons (cf.
Popper, 1982), consciousness (via the prefrontal cortex ?) may
perhaps alter the fabric of the brain itself, if not at least influence it for
the better (userware).
perception is S-R : S (stimulus) - R (response)
model (without userware or I)
sensation is S-I-R : S - I (internal process) - R
model (with userware)
Empirico-formal knowledge is a valid (corroborated & consensual), factual,
discursive, conceptual & propositional
interpretation of perception (cf.
Clearings, 2006). The paradigm of science consists of a system of
valid concepts arrived at through theory-formation (argumentation) and testing
(experimentation). At the core of the scientific paradigm (a system of valid
empirico-formal or scientific statements), a series of axioms are articulated. Great tenacity
is displayed not to change them. The closer one comes to the periphery, the more
accepted verisimilitude diminishes and statements less display the appearance of
truth. However, scientific knowledge is always conventional, and therefore
relative & historical. It is valid but mistaken, while ultimate knowledge is
unmistaken (cf. my
A Critique of a Metaphysics of Process, 2012).
Ideally (Quid Juris ?), scientific truth (a dyad) cannot be absolute truth
(a monad), but only the best of relative truth, arrived at by the interplay of
experimentation & argumentation (testing & arguing). Scientific knowledge is not
eternal, but an interdependent, dynamical display of differences (energies). It
is a provisional, conventional, fallible, conforming knowledge, a system of
synthetical judgments a posteriori, but the best available today to
conceive, grasp, hold, posit, conceptualize, categorize, etc.
as true, at least for today. A scientific paradigm is an object of the world of
information, the creative sum, mandala or "Gestalt" of material glyphs
concerning both the integration of perception (thalamus, angular gyrus), conscious
sensation and individual consciousness, the subject of experience (prefrontal
lobes). The way of the conceptual mind is in all cases a "concordia
discors", an armed truce of sorts.
Every observation, experience or sensation is
theory-dependent. Science, bound to a logic of finitude, cannot step outside
itself and eliminate the limitations of its own frame of
reference (the heuristic task of metaphysics). In a chaotic situation, fixation, petrification or fossilization are
hazardous. The best we can do, as conceptual rationalists, is to let object &
subject, testing & arguing go about and at some point judge by way of
Although sensate experience is a "stream" and not a sequence of static frames,
direct observation hic et nunc is ephemeral & anecdotal (individuum
est ineffabile). One cannot conceptually hold on to it, it comes,
stays a few moments and ceases. By fast repetition, the steady illusion of an
identical object is created. In fact, conscious sensation (experience, observation)
and its conceptualization (form) are fazbricated. In conscious sensation,
conceptual frames and perceptions are simultaneous and fastened (so
they cannot be isolated). Conceptualizing sensation, science produces
empirico-formal knowledge about sensate objects.
Sensations in epistemology, ethics and esthetics.
Wittgenstein wrote :
Wittgenstein, L. : Tractatus
Logico-Philosophicus, 5.5423, my italics.
"To perceive a complex means to perceive that its
constituents are combined in such and such a way. This perhaps explains that the
figure can be seen in two ways as a cube ; and all similar phenomena. For we
really see two different facts. (If I fix my eyes first on the corners a and
only glance at b, a appears in front and b behind, and vice versa.)"
With "internal process" or "interpretation" (I), both sensation & consciousness are targeted.
Sensation is the end result of a hierarchy of codes, beginning with transduction
and ending as a clear & sustained conscious awareness of sensate
objects. Sensation is the place where consciousness meets the world "out there".
Cogitation (mental objects) is the place where consciousness meets itself and
the work "in here".
Conscious sensation of "this" object as "that" (volitional association area) is
mediated by conceptuality (mental objects of volition, affects, thought &
sentience) and the abstract order (verbal association area).
The sensory system serves the cortex, offering afferent information to be
processed. In particular, sensoric input is processed together with handedness,
tool-making, symbolization, audition & speech. This verbal software is connected
with all association areas of the cortex. The prefrontal lobes confirm the
presence of these pre-sensate objects to a subject of conscious experience,
making them sensate. They are the executive area, processing (computing,
not causing, generating or producing) awareness of sensate & mental
objects, and self-awareness !
In the phrase : "I see You.", the neuronal sequence is reversed. First, there
are dynamical visual perceptions of shapes & colors moving from the receptor
organs to the thalamus and "named" by way of the angular gyrus ("You"), then
this "You" is actually "seen" by a subject of experience ("I"). This seeing and
this subject of experience seeing are simultaneous.
|afferents from receptor organs
So to consciously observe an object, is to grasp it and hold it before a
subject of experience. Sensations are always conscious and they are so because
resulting from a complex inner process, involving all association areas.
"All our knowledge begins with the senses,
proceeds thence to the understanding, and ends with reason. There is
nothing higher than reason for working up the material of intuition &
comprehending it under the highest unity of thought."
Kant, I. : Critique of Pure Reason,
In Kantian epistemology, the process of acquiring knowledge runs as follows :
empirical knowledge : a variety of direct, multiple, unordered, nameless
impressions (Hume), called "Empfindungen" (or perceptions) are
synthesized by the forms of representation "space" (related to geometry)
and "time" (related to arithmetics) and turned into "Erscheinungen" (or
phenomena). These representations reflect the structure of our receptive
apparatus, and are meant to structure sensations into phenomena ;
scientific knowledge : phenomena are only objectified by thought, but do
not constitute an object of knowledge, for this is realized in
propositions. The phenomena need to be structured by the 12 categories
of understanding, corresponding to 12 different types of propositions
(quantity, quality, relation and modality, each viewed from three
angels). This categorization of phenomena leads to object-knowledge
(synthetic propositions a priori). The categories are meant to
structure phenomena into object-knowledge ;
dialectic : metaphysical knowledge : the
variety of objects known is brought to a higher unity. A last,
sufficient ground is sought and found in the ideas of reason : "ego",
"world" and "God" (derived from the category of relation). These words
are not things and only serve understanding, nothing more. While
stimulating the mind's continuous expansion, these ideas regulate
understanding and bring it to a more comprehensive, reasonable unity.
They are meant to structure understanding into an immanent metaphysics.
The 2 forms of representation, 12 categories
(brought to unity by 3 ideas) make
the object possible, rather than vice versa. The human mind is
the active originator of experience, rather than just a passive
recipient of perceptions, as Hume (1711 - 1776) thought. The mind can not be a
tabula rasa, a "blank tablet", so Descartes (1596 - 1650) is right. The whole
transcendental system is innate. Even on the level of the transcendental
aesthetics, sensations, the only source of knowledge acknowledged, as
Locke (1632 - 1704) claimed, must always be processed to be recognized,
or they would just be "less even than a dream"
or "nothing to us".
Both sensations, representation and categorization are necessary to
constitute an object of knowledge.
This theory of knowledge is in tune with the neurophilosophy of
sensation. First there are perceptions ("Empfindungen",
"sinnliche Anschauung" or "Sinnlichkeit") relayed to the thalamus,
integrating & spatiotemporalizing them as phenomena ("Erscheinungen").
The latter are projected in the primary sensory cortex to be recognized
by the verbal association area and the attention association area as
object-knowledge. Kant's categorial scheme, although it does have
general characteristics (the neuronal structures of the areas), does not
yield synthetic propositions a priori (cf. Kant's acceptance of
foundationalism), but a series of conceptualization (of sensations), or perceptions
molded in an individual cognitive framework a posteriori. The higher order
organization of the mind by reason, is executed by the prefrontal lobes.
Although the pair perception/sensation plays a fundamental role in
epistemology, it is not without importance in ethics & esthetics. In
both, the need to distinguish between the input of the senses
(perception) and the irreducible interpretation of the conceptual mind
crucial and calls for a critical analysis of sensation. We cannot accept
our sensate information at face value, but distinguish between the
"raw" sense-data we are bound to affirm and the elaborate appearance of sensate objects
in simple to complex conceptual frameworks.
Although the conceptual mind is unable to eliminate interpretation to
witness the absolute data, it can introduce elaborate comparisons and
try to integrate information from as many subjects of experience as
possible. Insofar as an intersubjective consensus is at hand and
sensations are repeated over and over again, the subjective margin may
be reduced, although never completely eliminated (the scientific
language game has no privileged access to naked perception). Moreover,
as ultimate analysis shows, the mind may enter nondual, non-conceptual
cognition, and prehend objects directly, without conceptualizations.
Perhaps at this level, sensation comes closer to perception (as mystics
13. The argument of illusion.
For Shankara (788 - 820), the main representative of Advaita-Vedânta and
an important renewer of Hinduism after the success of Buddhism in India,
"mâyâ" (deception, illusion, enchanting display) is a universal principle
inseparably united with Brahman, the absolute.
As universal ignorance or cosmic illusion, "mâyâ" draws a veil over
Brahman and so confuses our vision, making us witness diversity rather
than unity. Because of illusion, we consider sensate objects to be
separate entities with definite characteristics. Here we are in
error, and witness illusion rather than true reality. The
origin of ignorance is the superimposition of unreal objective
conditions on what is truly at hand (adhyâsa). Moroever, the transfer of an object (a sensate
not-I) along with its accidents to the subject (the I), is deemed false
knowledge ("avidyâ"), mixing up reality with unreality,
incapable of distinguishing transient from intransient and real from unreal.
In the famous simile, we fear a coiled snake, while it is only a rope. In the
Vedanta, the key is always
to discriminate (viveka) between the real (Brahman, the absolute) and
the unreal (mâyâ, the relative). This eliminates ignorance.
To take away "avidyâ" brings enlightenment (samâdhi), destroying past &
future "karma" (or operational causes). Only the "karma" already bearing
fruit, sustaining this present life has not yet vanished. The
"jîvanmukta" ("one liberated while still alive"), witnesses how he
experiences activities caused by "prârabdha karma" (which can not be
prevented), but continuously without mixing up reality.
In the Buddhadharma, eliminating the substantial idea of Brahman, illusion is
things not appearing as they are. They appear as substances existing from
their own side, but when
analyzed, they are merely processes, nothing more.
Critical thought (cf.
Clearings, 2006) also draws a radical
distinction between absolute truth and relative truth, between the
Real-Ideal (Kant's "Ding-an-sich") and scientific empirico-formal
propositions a posteriori. Avoiding dogmatism (the unchangeable
yes) & skepticism (the unbreakable no of dogmatic negation), criticism (the open maybe) also
steers away from dogmatism or skepticism regarding absolute reality :
dogmatic affirmation : absolute truth and
conceptual rationality overlap (cf. fideism, idealism, spiritualism, realism,
materialism, logical positivism, scientism). There is only the conceptual mode
of thought to penetrate the absolute ;
skepticism or dogmatic negation : absolute truth cannot be known (the divide cannot be bridged). There is no mode of thought
enabling the recognition of the absolute Real-Ideal.
Universal illusion cannot be identified, for positing "mâyâ" turns it
into something particular, contradicting its universality. Neither can
exclude universal illusion by assuming "being" equals "being known in
then we move ad hoc from what we assume to be the case to the
affirmation of being as knowable as such (cf. the critique of foundationalism).
We assume the mental coincides (represents) the extra-mental and
move from this assumption to the affirmation this must be the case. This move
is unlogical. Classical metaphysics makes this category mistake (assumptions are not
certainties). Metaphysical realism (mind corresponds with reality) and
metaphysical idealism (mind makes reality) are extremes to avoid.
Although we must assume facts are the place where conceptual rationality &
the absolute coincide,
and must think the ultimate consensual correspondence (or Real-Ideal), we cannot
eliminate the possibility conceptual rationality is self-deluded and, as an
illusion-machine, superimposes its own dual display upon the world it
sensates and experiences, living out, as if on stage, its own projections in the "mirror" of the world "out there". In other
words, in order for knowledge to be
possible, we must suppose the absolute to be knowable, even if this is not the
case or only partially so. Indeed, conceptual knowledge could well be
illusionary, i.e. altogether different from the Real-Ideal. How can this not
humble the true scientist ?
Neurological executants are skilled cortical performers backing this interesting state
of affairs. The neurophilosophy of sensation clarifies the difference between
perception and sensation. The objects we sensate appear as they do because of
our interpretation and, as long as conceptual rationality is at hand, this
cannot be put to rest or eliminated. This "interpretation" is not something
"added" to perceptions, and, by some method, subtracted. The association
areas process the construction in which the sensate objects appear as entities
(cluster of events) with accidents (quantity, quality, relation, modality,
etc.) and this by a subject of experience. Before they "enter" these areas,
they have not been introduced to the overall modular activity of the
neocortex, the concert of interpretations with an attention area mediating
the will of the conductor. Once this happens, the end relay of perception
transforms into sensation, for there is interpretation (fabrication) and a subject of experience facing a
sensate object of experience.
S(ensation) = P(erception) . I(nterpretation), with I ≠ 1.
The argument of illusion can be explained in objective & subjective terms :
normally, the subject of experience never faces
the totality of changes caused, so we must assume, by particles & forces acting as a constant stream
of stimuli on the surface of the receptor organs ; they are unconscious.
Only after a series of complex, unconscious alterations (transduction, relays,
integration & projection) is the cortex informed (primary sensory area), in its own language,
about the perceived states, events, occurrences & objects. But, this thalamic
projection, in accord with the language of the cerebrum, into the neocortex is
not yet sensation. This it only becomes after the afferent pathways enter the
verbal association area, immediately connecting them with the attention
association area (while the primary sensory area has
few connections with the prefrontal lobes !). Our sensations,
because of their irreducible and pertinent interpretative, constructive,
conceptual, personal nature, could be a kind of fata morgana or mirage, composed
of distorted sensory items. Ambiguity is the least one can say of the direct
observation of sensate objects ;
subjective : the most objectifying operator of
consciousness, namely cognition or mind, works in various modes. In the
ante-rational mode (with its mythical, pre-rational & proto-rational modes), sensate objects appear in contexts and have no meaning
outside these. In rational, conceptual thought, which is formal and critical,
the theoretical connotations grasped by the subject of experience make it
impossible to witness sensate objects devoid of interpretation. Even if
so-called "subjective factors" are reduced or eliminated, it cannot be
conceptually known whether a collective mirage is
at hand or not.
Likewise, in creative thought, the own-Self cannot be designated without its
ideas and although a panoramic view is established, at best, observation is but
the view of one individual own-Self. Finally,
although nondual thought recognizes the nature of mind directly and hence moves
beyond interpretation, its wisdom is non-verbal and/or poetical and shows in what is done
& not done (cf.
Does the Divine Exist ?, 2005,
Behaviours, 2006 &
Intelligent Wisdom, 2007,
A last word about unsubstantiality, the
lack of inherent existence or
"substance", i.e. "sensate objects" existing in and for themselves. If sensation
is fabricated perception, then clearly the category of "substance" refers to the
mental habit of attributing "eternal" states to sensate objects, for
perceptions are a flowing stream of impressions, not fixed objects existing
solidly in and of themselves, from their own side. This "nature" of things is
therefore the outcome of a
false ideation, a conventional halting of the ongoing stream of changes which is
totally dependent of a decision ad hoc by some subject of experience or a
community of such subjects. Paradigm paralysis is precisely the inablility of
the scientific community to reckon the spatiotemporality of perception and
sensation. Of course, conceptually, we must assume "something" causes perception,
but in fact
this is probably only a stream of differential inputs, (vector) products of differences