Subjectivity and the Phenomenal World
Copyright © 2011 Arnold Trehub. Permission granted to distribute in any medium, commercial
or non - commercial, provided author attribution and this copyright notice remains intact
A particular system of brain mechanisms, called the retinoid system, is proposed as the evolutionary adaptation responsible for the existence of subjectivity and our sense of being here in a surrounding 3D world. The structural and dynamic properties of the retinoid system successfully predict a novel conscious experience in which the brain constructs a vivid visual representation of an object moving in space without a corresponding image projected to the retinas. Implications of the retinoid system for human creativity and our scientific understanding of the universe are suggested.
KEY WORDS: consciousness, 3-D world, brain,
We are each born with a system of brain mechanisms that constitute the full scope of our entire phenomenal universe. The structure and dynamics of this crucial brain system actually construct the world of our experience. What we call consciousness is the presence of this world for us. Consciousness did not exist before a creature was able to represent something somewhere in a perspectival relationship to a fixed internal "point" of origin - a transformative evolutionary event that ushered in the dawn of the first-person perspective - subjectivity and consciousness. To this extraordinary biological development we owe the possibility of all of our past and present conceptions of everything that is in our cosmos. Here is the key question: What biological mechanism emerged that enabled subjectivity and set us on a path by which we can now engage in our present discourse about consciousness? My proposal is that a unique brain system with a particular kind of neuronal structure and dynamics - the retinoid system (Trehub 1977, 1991, 2007) -- is the essential generator of our conscious experience. The structural and dynamic properties of the retinoid system enable it to register and appropriately integrate disparate stimuli into an egocentric representation of one's volumetric surround - the world around us. This system of neuronal mechanisms composes an internal egocentric space that receives Input from all sensory modalities and, in recurrent fashion, projects its excitatory neuronal patterns back to each sensory modality. It organizes its multi-sensory features into a coherent global representation of 3D space. All the sensory features of objects and events in retinoid space are organized in proper spatiotemporal register, called feature binding. For example, if a red car were to travel from left to right in your field of view, the retinoid representation of its color would be contained within the contour of its shape, and both color and shape would move in concert left to right within your egocentrically organized retinoid space. Each sensory modality is served by a particular kind of neuronal mechanism called a synaptic matrix (Trehub 1991). The synaptic matrix is a self-organizing brain mechanism that has the capacity to learn and classify complex stimulus patterns, store them in long-term memory, and recall images of them in the absence of external stimulation. Synaptic matrices are specialized processors; each serves only one kind of sensory feature; e. g., for visual shape, for color, for motion, for taste, etc. It is the role of the retinoid system to integrate signals from these disparate sensory modalities, widely separated in the brain, into a single coherent representation of the surrounding world.
The rich content of our sense of the world around us is provided by reciprocal evocation among sensory images and their neuronal tokens embodied in the recurrent loops of the synaptic matrices in parallel coupling with the retinoid system. If we think in metaphorical terms of a theater of consciousness within the brain, then retinoid space would correspond to the bright stage of the "theater" on which we are a participant. This stage is our conscious content. The synaptic matrices in the various sensory modalities and the other cognitive mechanisms which categorize and evaluate the patterns of neuronal activity (the objects and events) presented on the retinoid "stage" would correspond to something like a critical observing audience in the dark (unconscious) part of the theater (Trehub 2007).
Notice in Fig. 1 that that there are neuronal pathways from the body's sensory receptors (R1and R2 in the diagram) to the brain's unconscious sensation to action processors, then from these neuronal mechanisms to the neuromuscular structures for overt action. It is assumed that all sentient and motile preconscious organisms have this kind of sensory-motor system. However, with the emergence of the retinoid system in the course of creature evolution, an entirely new kind of brain mechanism with new possibilities for adaptive action appeared in the world.
Some investigators have claimed that consciousness
depends on particular kinds of quantum events
in the brain's neuronal circuits. On the
basis of our present understanding of quantum
electrodynamics we should expect quantum
events to be relevant to all biophysical
processes at a fundamental level. However,
I would argue that if particular kinds of
quantum events are selectively determinate
for conscious content, they must conform
in some way to the structural and dynamic
properties of the retinoid system. With a
nod to the anthropic principle, I suggest
that the entire conceptual edifice of modern
science is a product of biology and is necessarily
constrained by the conscious-cognitive structure
and dynamics of the human brain. The cosmos
as it is subjectively represented in the
retinoid system of the human brain is the
only cosmos we can think about.
A key feature of the representational space within the retinoid system is that it is organized around a fixed cluster of cells which constitute the neuronal origin - the 0,0,0 (X, Y, Z) coordinate -- of its 3D spatiotopic neuronal structure. All phenomenal representations are constituted by patterns of neuronal excitation on the Z-planes of retinoid space. I have proposed that the fixed spatial coordinate of origin in the Z-plane structure can be thought of as one's self-locus in one's phenomenal world, and I designate this central cluster of neurons as the core self (I!) (Trehub 1991, 2007).
Our consciousness is no more nor less than the current content of our phenomenal world, and on this I base my working definition of consciousness as follows:
Consciousness is a transparent brain representation of the world from a privileged egocentric perspective.
In the development of the physical theory of light, the double-slit experiment was critical in demonstrating that light can be properly understood as both particle and wave. Similarly, I believe that a particular experiment - a variation of the seeing-more- than-is-there (SMTT) paradigm - is a critical experiment in demonstrating that consciousness can be properly understood as a complementary relationship between the activity of a specialized neuronal brain mechanism, having the neuronal structure and dynamics of the retinoid system, and our concurrent phenomenal experience.
If a narrow vertically oriented aperture
in an otherwise occluding screen is fixated
while a visual pattern is moved back and
forth behind it, the entire pattern may be
seen even though at any instant only a small
fragment of the pattern is exposed within
the aperture. This phenomenon of anorthoscopic
perception was reported as long ago as 1862
by Zöllner. More recently, Parks (1965),
McCloskey and Watkins (1978), and Shimojo
and Richards (1986) have published work on
this striking visual effect. McCloskey and
Watkins introduced the term seeing-more-thanis-there
to describe the phenomenon and I have adopted
it in abbreviated form as SMTT. The following
experiment was based on the SMTT paradigm
As soon as the figure is in motion, subjects report that they see, near the bottom of the slit, a tiny line segment which remains stable, and another line segment in vertical oscillation above it. As subjects continue to increase the frequency of horizontal oscillation of the almost completely occluded figure there is a profound change in their experience of the visual stimulus.
At an oscillation of ~ 2 cycles/sec (~ 250 ms/sweep), subjects report that they suddenly see a complete triangle moving horizontally back and forth instead of the vertically oscillating line segment they had previously seen. This perception of a complete triangle in horizontal motion is strikingly different from the tiny line segment oscillating up and down above a fixed line segment which is the real visual stimulus on the retinas.
As subjects increase the frequency of oscillation
of the hidden figure, they observe that the
length of the base of the perceived triangle
decreases while its height remains constant.
Using the rate controller, the subject reports
that he can enlarge or reduce the base of
the triangle he sees, by turning the knob
counterclockwise (slower) or clockwise (faster).
Results: As the experimenter varies the actual height of the hidden triangle, subjects successfully vary its oscillation rate to maintain approximate base-height equality, i. e. lowering its rate as its height increases, and increasing its rate as its height decreases.
This experiment demonstrates that the human brain has internal mechanisms that can construct accurate analog representations of the external world. Notice that when the hidden figure oscillated at less than 2 cycles/sec, the observer experienced an event (the vertically oscillating line segment) that corresponded to the visible event on the plane of the opaque screen. But when the hidden figure oscillated at a rate greater than 2 cycles/sec., the observer experienced an internally constructed event (the horizontally oscillating triangle) that corresponded to the almost totally occluded event behind the screen. The experiment also demonstrates that the human brain has internal mechanisms that can accurately track relational properties of the external world in an analog fashion. Notice that the observer was able to maintain an approximately fixed one-to-one ratio of height to width of the perceived triangle as the height of the hidden triangle was independently varied by the experimenter.
These and other empirical findings obtained
by this experimental paradigm were predicted
by the neuronal structure and dynamics of
a putative brain system (the retinoid system)
that was originally proposed to explain our
basic phenomenal experience and adaptive
behavior in 3D egocentric space (Trehub,
1991). It seems to me that these experimental
findings provide conclusive evidence that
the human brain does indeed construct phenomenal
representations of the external world and
that the detailed neuronal properties of
the retinoid system can account for our conscious
The ability to move excitation from the source point of the self-locus (I!) to selected regions within the depth (Z-planes) of retinoid space also provides an important means of selective attention. The projection of neuronal excitation from the excitatory source of the core self to a target of interest in 3D retinoid space constitutes a selective shift of attention which is realized by an excursion of the heuristic self-locus (I!*; see Fig. 2). Neurons in regions of a retinoid that are stimulated by the added local excitation of a heuristic self-locus excursion are preferentially primed and marked relative to othercells in retinoid space. Cells in a primed region respond more quickly and vigorously than those in unprimed regions.
An important feature of the heuristic self-locus
is its property of inducing excitatory traces
or patterns of cellular activity in accordance
with its movement through retinoid space.
We can think of these excitatory images as
similar to the patterns drawn by a stylus
on a display board. These self-locus traces
might represent unimpeded travel routes between
regions of interest, they might represent
barriers to be avoided, or they might be
retinoid images of our own imaginative construction
serving us as cognitive maps or internal
sketches to be used for many different purposes.
The capability for invention, trivial and great, is arguably the most consequential characteristic that distinguishes humans from all other creatures. Our cognitive brain is especially endowed with neuronal mechanisms that can model within their biological structures all conceivable worlds as well as the world that we directly perceive or know to exist. External expressions of an unbounded diversity of brain-created models constitute the arts and sciences and all the artifacts and enterprises of human society (Trehub, 1991).
Our retinoid system together with a specialized preconscious brain mechanism for learning, long-term memory, and imaging, which I call a synaptic matrix, make creative modeling possible. A detailed description of the basic neuronal design of the synaptic matrix, as well as the structure and dynamics of the retinoid system, is given in Trehub 1991 (The Cognitive Brain). Synaptic matrices in all of our sensory modalities serve learning, memory, recognition, recall, and imaging of sensory features and events, while the retinoid system receives feedback signals from the imaging matrix of each modality to organize a coherent global layout of objects and events in our egocentrically organized retinoid space.
The conscious brain constructs the world of our experience by inserting and arranging on the Z-planes of retinoid space selected patterns of exteroceptive and interoceptive sensory patterns together with images recalled from the memory stores of synaptic matrices. The retinoid mechanisms are able to create phenomenal representations of novel objects and events by parsing objects or their parts in existing representations and rearranging these excitatory neuronal patterns in new combinations projected into retinoid space. The analytic mechanisms of the cognitive brain (shown below the dotted line in Fig. 3) can then evaluate the novel retinoid images in terms of their practical or theoretical utility. These putative brain mechanisms have been described in detail (Trehub 1991).
On the basis of Fig. 3, we can say that damage
to any of the mechanisms below the dotted
line would result in cognitive impairment
with a sparing of consciousness. But if the
synaptic link between the self-locus cells
in the retinoid's Z-plane and its neuronal
token (I!) below the dotted line were broken
or damaged we would expect a loss of consciousness.
Taking this into account, we might conjecture
that the reason a sharp blow to the head
can cause a loss of consciousness is precisely
because the jolt can effectively interrupt
synaptic communication between the self-locus
neurons in the retinoid structure and I!,
which is in an excitatory feedback loop with
the retinoid's self locus (the core self),
and which provides a gateway to the rest
of the cognitive system.
Can the retinoid model answer the daunting questions that have long perplexed the search for a scientific understanding of consciousness? An important consideration in making an assessment is whether the theoretical model enables the scientific community to perform reasonable empirical tests of its implications. In this respect, I have suggested that a science of consciousness requires the adoption of a bridging principle between the first-person subjective description of conscious content and a third-person objective description of conscious content (Pereira Jr, A. et al 2010). To this end, I have proposed the following principle:
For any instance of conscious content there is a corresponding analog in the biophysical state of the brain.
The objective, then, is to formulate brain
mechanisms that can generate proper analogs
of conscious content. Application of this
bridging principle led to successful predictions
about subjects' conscious experiences in
the SMTT experiment on the basis of the detailed
structure and dynamics of the retinoid system.
It should be added that there are many more
previously puzzling subjective phenomena
that are straightforwardly explained by the
causal properties of the retinoid system,
among them, the moon illusion, size constancy,
and motion after-effects (see Trehub 1991,
pp. 89-93 and pp. 239-255). A positive aspect
of the retinoid theory, beside its explicit
account of subjectivity and phenomenal consciousness,
is its ability to explain human creativity
on the basis of the normal operation of plausible
brain mechanisms. This, together with the
well founded supposition that the retinoid
structure of the brain is an advanced evolutionary
adaptation, adds credence to the theoretical
model. Moreover, the implications of the
retinoid model for understanding the source
of our scientific concepts lends substance
to the weak version of the anthropic principle
(Barrow and Tipler 1986). In addition to
extending the retinoid model and further
testing its implications, one would want
to see others pursue the scientific challenge
of formulating an alternative testable model
that can do a better job of explaining subjectivity
and the brain mechanisms that present us
with our phenomenal world.
Our phenomenal world, the world of everyday experience, the world in which we try to thrive and probe for understanding, is an amazing product of biological evolution. The big questions that science now tries to answer could not be posed before the evolutionary emergence of the brain's retinoid system. It is this biological system which gives us subjectivity -- a sense of a self centered in a surrounding universe.
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