Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Perceptual Categorization

The neural network of the brain identifies objects by a rapid hierarchy of ever-finer-grained categorization of features of the object. The categorization process relies fundamentally on the associative property of memory to activate a sparse pattern of neuronal connectivity, which represents the object.

In the visual network for example, the image from the eyes is parsed into feature segments of color, orientation, etc. in the early visual stages and is further processed in the association cortices, parietal lobe and is ultimately identified in a fraction of a second in the inferotemporal cortex.

Perceptions are unified wholes, shot through with memories, hopes, prejudices, and other internalized cognitive idiosyncrasies. (Greenfield; Human Brain, 52)

Consciousness a Convolution of the Perceptual Mental Image with the Sense-of-Self

Gestalt laws of grouping    include proximity,    similarity,   continuation,    and closure. (Crick; Astonishing Hypothesis, 37)

Gestalt laws of perception   should not be regarded as rigid laws    but as useful heuristics. (Crick; Astonishing Hypothesis, 41)


Research Study — Active Cortical Dendrites Modulate Perception

Research Study — Cognitive Processes Influence on Pain Perception

Link to — Perception and Memory

Link to — Scatter of Topics for Spreading Activation functionality

Research Study — Oxytocin Balances Cortical Inhibition with Excitation

Separate ‘what’ and ‘where’ pathways for visual object identification and location.

‘What’ Pathway for Visual Object Identification


‘Where’ Pathway for Distance Perception, 3D Object Perception


Spreading Activation Theory for Semantic Memory

According to spreading activation theory, semantic memory is organized on the basis of semantic relatedness or semantic distance. (Baddeley,; Memory, 119)

The spreading activation model has generally proved more successful than the hierarchical network model. (Baddeley,; Memory, 121)

The spreading activation model could be implemented by the associative property of memory.


Link to – Perception functionality

Link to — Topics for Speech Perception


Research Study — Topographic Numerosity in Parietal CortexNumerosity, the set size of a group of items, is processed by the association cortex. Animals, infants, and tribes with no numerical language perceive numerosity although they cannot count or use symbolic representations of number.  Topographic representations, common in the sensory and motor cortices, can emerge within the brain to represent abstract features such as numerosity.  These organizational properties of topographic principles extend to the representation of higher-order abstract features in the association cortex.


Perception of Pain

Situated at the interface of body and mind,     the pain system     is only a few synapses between the biophysics of stimulus transduction    and the mysteries of perception, affect, and belief . (Devor; Pain Networks, 702)

The sensation of pain    is initially processed in a small structure called the insula ("island"),    which is folded deep beneath the temporal lobe on side of the brain. (Ramachandran; Tell-Tale Brain, 39)

From the insular    the pain information is then relayed    to the anterior cingulate in the frontal lobes. (Ramachandran; Tell-Tale Brain, 39)

It is in the anterior cingulate    that you feel the actual unpleasantness --    the agony and awfulness of pain --    along with an expectation of danger. (Ramachandran; Tell-Tale Brain, 39)


Patternicity -- the tendency to find meaningful patterns

Perceptions of natural scenes, speech, music, and body image as well as our occasional illusions can be attributed largely to the unique organization of the isocortex. (Buzsáki; Rhythms of the Brain, 277)

No matter how strongly men are drawn to the female form,    or women to a man's physique,    we know of no part of the human brain    dedicated to analyzing the nuances of bulging biceps or the curves of firm buttocks or breasts. (Mlodinow; Subliminal, 38)

Our brains are belief engines, evolved pattern recognition machines that connect the dots and create meaning out of the patterns that we think we see in nature. (Shermer; Believing Brain, 59)

Patternicity -- the tendency to find meaningful patterns in both meaningful and meaningless noise. (Shermer; Believing Brain, 60)

Perception of likeness is very much bound up with that of difference. (James; Principles of Psychology - Volume 1, 528)

Perceptions generated by the sensory systems recruit the amygdala, which colors perception with emotion, and the hippocampus, which stores aspects of perception in long-term memory. (Kandel; Principles of Neural Science, 319)

The dichotomies in perceptual categorization are exemplified in bistable perceptual categorization.

Fusiform Face Area

There is a discrete part of the brain that is used to analyze faces.    It is called the fusiform face area. (Mlodinow; Subliminal, 38)

Expressions are a key way we communicate    and are difficult to suppress or fake,    which is why great actors are hard to find. (Mlodinow; Subliminal, 38)

Facial expressions are controlled in large part by our unconscious minds. (Mlodinow; Subliminal, 38)

Facial recognition neural connectivity synaptic efficacies were built into our brains by evolution because of the importance of the face in establishing and maintaining relationships, reading emotions, and determining trust in social interactions.  (Shermer; Believing Brain, 69)

In the temporal lobes of the brain the fusiform gyrus is actively involved in facial recognition. (Shermer; Believing Brain, 70)

There are two separate neural pathways for processing faces -- one for processing faces in general and another for processing facial characteristics in particular. Shermer; Believing Brain, 70)


Research Study — Perception, Face Recognition

Research Study — Facial Recognition Improves from Infancy to Adulthood


Degeneracy in Perceptual Categorization

Sensory signal patterns interact with the vast neural network of synaptic efficacies to form activated neural signal patterns constituting perceptions of consciousness.

The pattern of synaptic strengths in the ensemble of cortical and subcortical neurons has the property of degeneracy as pointed out by Edelman.  An input signal pattern will distribute itself in the cortical network with variability in the ensemble of pathways it invokes, each time it appears as an input.

Countless examples of degeneracy in the brain. The complex meshwork of connections in the thalamocortical system assures that a large number of different neuronal groups can similarly affect the output. A consequence of degeneracy is that certain localized neurological lesions may often appear to have little effect. (Edelman; Universe of Consciousness, 87)

Perception an Act of Classification

Perception is an act of classification of objects by a network-like systems of connections formed by prior experience with those objects. (Fuster; Cortex and Mind, 8)

Any reader easily retrieves a single meaning of at least 50,000 candidate words, in the space of a few tenths of a second, based on nothing more than a few strokes of light on the retina. (Dehaene; Reading in the Brain, 42)

The human brain is the archetype of a massively parallel system where all neurons compute simultaneously. (Dehaene; Reading in the Brain, 44)

Categorization mechanisms work through global mappings that necessarily involve our bodies and our personal history. (Edelman; Bright Air, 152)

We often use semantic memory successfully by inferring the right answer. (Baddeley,; Memory, 117)

Perception consists in the classing of objects by the binding of characteristics that have co-occurred in the past and thus have been associated by prior experience. (Fuster; Cortex and Mind, 61)

We perceive what we remember as well as remember what we perceive. (Fuster; Cortex and Mind, 84)


Link to — Pathology — Perception Software in Medical Imaging


Binocular Rivalry to Study Neural Perceptual Organization

Since virtually any pair of dissimilar images can be made to rival when presented dichoptically, binocular rivalry provides a powerful paradigm to study the neural correlates of perceptual organization and visual awareness. (Lumer; Binocular Rivalry, 231)


A neuron doctrine for perceptual psychology?

H B Barlow, Department of Physiology-Anatomy, University of California, Berkeley, 1972

· The sensory system is organized to achieve as complete a representation of the sensory stimulus as possible with the minimum number of active neurons.

· Trigger features of sensory neurons are matched to redundant patterns of stimulation by experience as well as by developmental processes.

· Perception corresponds to the activity of a small selection from the very numerous high-level neurons.

· High impulse frequency in such neurons corresponds to high certainty that the trigger feature is present.


Perceptual Categorization Facilitated and Enriched by Language

Language facilitates detailed thoughts and communication of perceptions and memories.

During the past 30 years or so, language related to computers has come into use with specialized nouns, verbs, adjectives, and adverbs.

In molecular biology, an entire vocabulary has involved and continues to expand exponentially to delineate the developing understanding and knowledge.


Perception at a given moment is represented by a small percentage of coherently oscillating cellular elements over the whole thalamocortical system.  (Llinás & Paré; Brain Modulated by Senses, 14)

A perception is a widely distributed, sparse, neural network (cognit) (Fuster; Cortex and Mind14) of neuronal activity overlaid on the brain's ensemble (the self) of synaptic strengths.  The gossamer pattern of neural activity comprising a perception is sparse and highly differentiated, yielding great specificity in the categorization, and yet highly integrated to combine the active synaptic pattern into a perception.

The various kinds of information we have about an object (e.g. what humans use it for, what it does, its visual properties, its taste) are distributed in different brain areas. (Baddeley,; Memory, 125)

In ways that remain mysterious, we somehow manage to integrate all of these kinds of information    rapidly and automatically when we think about any given concept. (Baddeley,; Memory, 125)

Exquisite specificity cortical representation arises from two basic assumptions: (1) any neuron population within the web can be connected, directly or indirectly (i.e. several synapses), with practically any other and (2) the strength of neuron connectivity between them can vary greatly in terms of the number of fiber connections and in terms of synaptic bond. (Fuster; Cortex and Mind, 142)

“Exquisite specificity” and “highly differentiated” are synonymous descriptions.

From the enormous richness of anatomical relations between cortical neurons and a wide range of the strengths of those relations derive the immense capacity and specificity of human memory. (Fuster; Cortex and Mind, 142)

The neural activity pattern of the perception forms the dynamic core of consciousness in the thalamocortical system.

Perception involves simultaneous parallel processing that combines top-down knowledge with bottom-up perceptual input. (Thagard; Brain and the Meaning of Life, 100)

Input Signal Propagates into the Best Synaptic Fit

The pattern of pathways followed by an input signal corresponds most closely to the pattern of synaptic efficacies that has been established in the network by genetics and prior experience. The signal activates a widespread but sparse memory trace that most closely conforms to a synaptic efficacy pattern established by prior neural activity. The neural network’s billions of synaptic efficacies, molded by biochemical plasticity in the short term and protein synthesis in the long term, mediate a neural mechanism for the synaptic efficacy distribution representing a person’s individuality and memory.

Research Study — Cortical Connectivity and Sensory CodingEach sensory stimulus causes a complex pattern of activity in the neuronal populations of multiple cortical areas. The relationship between sensory stimuli, and the firing patterns they evoke, defines the ‘neural code’ of the corresponding populations.


Feedforward inhibition serves to impose a temporal framework on a target area on the basis of inputs received. (Andersen; Hippocampus Book, 299)

As a vague metaphor, consider that the input signal propagates through the neural network, settling into "its most comfortable fit" via the highest synaptic efficacies, "hand in glove fashion."  This propagation of the input signal via its closest synaptic fit activates a specific memory, and concomitantly, the dynamic core of consciousness.

In studies using functional magnetic resonance imaging (fMRI) in humans, multivariate pattern analyses demonstrate the presence of specific patterns of brain activity for certain objects seen or heard by the subject. (Damasio; Self Comes to Mind, 133)

At any moment during an animal's life, only a small fraction of neurons will be strongly activated by natural stimuli. (Foldiak; Sparse Coding, 897)

In the act of perception, sensory impulses come to a perceptual apparatus that is ready-made for them, much as in the immune system a pattern of antibodies in ready-made for a wide variety of antigens (Edelman, 1987). (Fuster; Cortex and Mind, 91)

Perception a Cascade of Processes

Perception would operate on the basis of a cascade of processes going in one direction.  The cascade would extract, step-by-step, more and more refined signals, first in the sensory cortices of a single modality (e.g., visual) and later in multimodal cortices, those that receive signals from more than one modality (e.g., visual, auditory, and somatic). (Damasio; Self Comes to Mind, 137)

The perception cascade would follow, in general, a caudo-rostral direction in the culminating and anterior temporal and frontal cortices, where the most integrated representations of the ongoing multisensory apprehension of reality are presumed to occur. (Damasio; Self Comes to Mind, 137)


Research study — Perceptual Learning  in Early Visual CortexResults indicate that the adult early visual cortex is so plastic that mere repetition of the activity pattern corresponding to a specific feature in the cortex is sufficient to cause VPL of a specific orientation, even without stimulus presentation, conscious awareness of the meaning of the neural patterns that participants induced, or knowledge of the intention of the experiment.


Bidirectional Search by Top-Down and Bottom-Up Streams Seeking to Meet

Counterstreams sequence-seeking model is a bidirectional search performed by top-down and bottom-up streams seeking to meet. (Ullman; Sequence Seeking Counterstreams, 270)

Activity of neurons in the very early areas is determined by their connections with other neurons in those areas as well as top-down, "feedback" connections emanating from the temporal or parietal lobes. (Logothetis; Window on Consciousness, 88)


Perception-Action Cycle uses Reentry and Recursion

Joaquin Fuster’s Perception-Action Cycle uses reentry and recursion on all hierarchical layers between the frontal motor cortical areas and the posterior sensory cortical areas.


Continuity of Consciousness

Our continuity of consciousness occurs as a chain of associations devolved around an epicenter. "Ripples" on one gestalt spread out to ever more remote associations, so a new epicenter starts to recruit neurons into a gestalt. This new gestalt supplants the original, and our consciousness subtly shifts. (Greenfield; Centers of Mind, 105)

Short-Term Memory and the Dynamic Core

Short term memory that is fundamental to primary consciousness reflects previous categorical and conceptual experiences. The interaction [dynamic core] of the memory system with current perception occurs over periods of fractions of a second.  (Edelman; Universe of Consciousness, 109)


Research observations indicate that a coherent perception of an object involves synchronization of large cortical areas. (Buzsáki; Rhythms of the Brain, 245)

Induced gamma activity emerges at a variable latency between 150 and 300 ms after stimulus onset, approximately at the time when stimuli acquire meaning. (Buzsáki; Rhythms of the Brain, 244)

In the course of perceptual processing the stimulus makes contact with long-term memory prior to the point at which awareness occurs. (Shevrin; Psychological Unconscious, 545)

Consciousness is bound up with processes that involve a limited capacity system.  This imposes a serial order upon what are essentially widespread parallel processes initiated by a stimulus. (Shevrin; Psychological Unconscious, 545)


Perception and Memory Share the Same Neural Substrate

A new percept leads to a new memory by building upon old memory. (Fuster; Cortex and Mind, 112)

From the point of view of neurobiology, knowledge, memory, and perception share the same neural substrate. (Fuster; Cortex and Mind, 112)

Memory is fundamentally an associative function. (Fuster; Cortex and Mind, 113)

Throughout the cerebral cortex, association becomes the essence of sensation, perception, and memory. (Fuster; Cortex and Mind, 8)

Perception and working memory are closely related.

Computer simulation shows that the operation of the prefrontal cortex in short-term memory and its relation to posterior perceptual networks, can be understood by the interaction of two weakly coupled attractor networks. (Rolls & Deco; Noisy Brain, 97)


Research study — Modularity of Categorization in Parietal Cortex


Categorization in Procedural Memory as well as Declarative Memory

The neural mechanism for categorization can be in declarative memory or in procedural memory, depending on the skill and experience level of the observer. I’ll give a few examples:

First: As any amateur birdwatcher knows, songbirds such as warblers can be identified by their coloration pattern, along with size, habitat, and behavior. Experienced birders become ever more skillful and rapid in identification as the initial declarative memory exercise of recalling pictures from the bird books is supplanted with procedural memory of ‘letting the brain do it’, which bypasses the hippocampus.

Second: An adult who is trying to learn a foreign language and is simply reading and listening to the language, will not be able to speak the language, although he or she will be able to understand fragments and perhaps get the gist of what is being said.

Classical music has a number of structural categorizations, which if they can be sensed and understood by the listener, can bring delight to the listener in addition the emotional enjoyment of the sound.

Binding by Temporal Coherence

Peter Millner and Christoph von der Malsburg -- spatially distributed cell groups should synchronize their responses when activated by a single object. (Buzsáki; Rhythms of the Brain, 238)

Representation of the various attributes of the visual world by distributed neuronal assemblies can be bound together harmoniously in the time domain through oscillatory synchrony. (Buzsáki; Rhythms of the Brain, 232)

Features processed in separate parts of the cortex by different sets of neurons are bound into a complex representation in a matter of 200 ms or so. (Buzsáki; Rhythms of the Brain, 232)

Love comes in at the eyes -- just one look may be all it takes -- visible cues help us determine in less than a second if we find another person attractive. (Horstman; Love, Sex, and the Brain, 96)

We remain agnostic with respect to the relevance of gamma oscillations to conscious perception. (Crick & Koch; Consciousness and Neuroscience, 46)

When presented with a visual image, primates can rapidly (<200 ms) recognize objects despite large variations in object position, scale, and pose. This ability likely derives from the responses of neurons at high levels of the primate ventral visual stream, which could construct a tolerant object representation by taking advantage of this natural tendency for temporally contiguous retinal images to belong to the same object. Tolerance ("invariance") may be learned from the temporal contiguity of object features during natural visual experience, potentially in an unsupervised manner.


Gestalts in Perception

Gestalt grouping for both vision and sound intelligibility.

Gestalt psychologists have long known that the whole is often faster recognized than its parts, indicating that object recognition is not simply representation of elementary features, but the result of bottom-up and top-down interactions, in harmony with the architectural organization of the cerebral cortex. (Buzsáki; Rhythms of the Brain, 243)

Autoassociative networks can recall the appropriate memory from the network when provided with a fragment of one of the memories. This is called completion. (Rolls & Deco; Noisy Brain, 31)

The probability for intra- and interariel response synchronization should reflect some of the Gestalt criteria for perceptual grouping. (Singer & Gray; Temporal Correlation, 1090)

The probability that distributed cells join an assembly should reflect the Gestalt criteria, i.e., features in images tend to group together to form objects. (Singer & Gray; Temporal Correlation, 1099)

As the features in an image change, the relationships among the activity patterns of the cells responding to those features should change in a way that reflects of the Gestalt properties of the image. (Singer & Gray; Temporal Correlation, 1100)

Locally emerging stable oscillators in the cerebral cortex are constantly being pushed and pulled by the global dynamics. (Buzsáki; Rhythms of the Brain, 120)

Despite the chaotic dynamics of the transient coupling of the oscillators at multiple spatial scales, a unified system with multiple time scales emerges. (Buzsáki; Rhythms of the Brain, 120)

Here are some examples of perceptual Gestalt in perceptual categorization.

Souls, spirits, ghosts complicate Realistic Perception

Souls, spirits, ghosts, gods, demons, angels, aliens, and talented designers, government conspiracies, and all manner of invisible agents with power and intention are believed to haunt our world and control our lives. (Shermer; Believing Brain, 87)

Combined with our propensity to find meaningful patterns in both meaningful and meaningless noise, patternicity and agency form the cognitive basis for shamanism, paganism, animism, polytheism, monotheism, and all modes of Old and New Age spiritualisms. (Shermer; Believing Brain, 87)

Many highly educated and intelligent individuals experience a powerful sense that there are patterns, forces, energies, and entities operating in the world. (Shermer; Believing Brain, 88)

Attractor Neural Networks for Gestalts

Autoassociative memories, or attractor neural networks, store memories, each one of which is represented by a pattern of neural activity. (Rolls & Deco; Noisy Brain, 31)

Perhaps the most important and useful property of autoassociative memories is that they complete an incomplete input vector, allowing recall of a whole memory from a small fraction of it. (Rolls & Deco; Noisy Brain, 35)

The simple emergent properties of associative neuronal networks such as generalization, completion, and graceful degradation can be realized very naturally and simply. (Rolls & Deco; Noisy Brain, 62)

A highly developed system of excitatory recurrent collateral connections between nearby pyramidal cells is a hallmark of neocortical design. (Rolls & Deco; Noisy Brain, 30)

Noise and spontaneous firing help to ensure that when a stimulus arrives, there are always some neurons very close to threshold that respond rapidly, and then communicate their firing to other neurons through the modified synaptic weights, so that an attractor process can take place very rapidly. (Rolls & Deco; Noisy Brain, 78)

Bistable Perception

Here are some examples of bistable perception in perceptual categorization.

Necker cube -- bistable vision -- visual information coming into the eyes remains the same, but the percept changes. (Crick; Astonishing Hypothesis, 212)

Bistable percepts. (Crick & Koch; Consciousness and Neuroscience, 41)

Metastability of ambiguous figures such as the Necker cube involve perceptual shifts initiated by eye movements. (Buzsáki; Rhythms of the Brain, 229)

It is not obvious where to look in the brain for the two alternative views of the Necker cube. (Crick & Koch; Consciousness and Neuroscience, 41)

The famous "duck-rabbit" example, can be perceived as either a duck or a rabbit. (Searle; Mind: A Brief Introduction, 100)

Brain has the ability to take a constant stimulus and treat it as either one perception or another in gestalt switching. (Searle; Mind: A Brief Introduction, 100)


Research study — Bistable Vision and the Prefrontal Cortex

Link to — Bistable Perceptual Categorization


Early Sensory Processing in Perception

According to one textbook on human physiology, the human sensory system sends the brain about 11 million bits of information in each second. (Mlodinow; Subliminal, 33)

The binding problem of early sensory processing refers to how early-stage, separately-processed stimulus elements are sorted and combined to form perceptually distinct complex stimuli. (Eichenbaum; Olfactory Perception and Memory, 192)

Early sensory cortices are the critical base for processes of image making. (Damasio; Making Images, 20)

Hypothesized that the early sensory  cortices of each modality construct, with the assistance of structures in the  thalamus  and the colliculi, neural representations that are the basis for images. (Damasio; Making Images, 20)

Each stage in the processing of visual information from the retina to cortical areas 20 and 21 can be regarded as having a hierarchical order with features in sequential array. (Eccles; Evolution of Brain, 126)

The visual field becomes progressively less specific. This increasing generalization results in a foveal representation for all neurons of areas 20 and 21. (Eccles; Evolution of Brain, 126)

In area TE of the temporal lobe, there are small neuronal assemblies uniquely active for features such as squares, rectangles, triangles, stars, etc.  More abstractly, there are small numbers of neurons that respond specifically to hands or faces, etc.  In some cases there are also representations of features of special significance to an animal. (Eccles; Evolution of Brain, 126)

Firing rate of a neuron is an ever-changing dynamic value that depends upon the momentary participation of the neuron in a neuronal assembly.

Hierarchical Visual Processing

Each stage in the processing of visual information from the retina to cortical areas 20 and 21 can be regarded as having a hierarchical order with features in sequential array. (Eccles; Evolution of Brain, 126)

The visual field becomes progressively less specific. This increasing generalization results in a foveal representation for all neurons of areas 20 and 21. (Eccles; Evolution of Brain, 126)

In area TE of the temporal lobe, there are small neuronal assemblies that are uniquely active for features such as squares, rectangles, triangles, stars, etc.  More abstractly, there are small number of neurons that respond specifically to hands or faces, etc.  In some cases their are also representations of features of special significance to an animal. (Eccles; Evolution of Brain, 126)

Two major parts of the inferotemporal cortex are: (1) the posterior part, which contains a subarea TEO that is specialized for fine discrimination of forms, and (2) an anterior part of the temporal lobe (sometimes labeled TE), which contains the mnemonic properties necessary for identification of an object. (LaBerge; Attentional Processing, 109)


Research Study — Perception of Objects Hierarchically in Occipitotemporal Cortices


Facial Recognition by Humans

Humans have an exquisite cortical functionality for recognizing faces.

Face recognition is typically reliant on structures in the right cerebral hemisphere. (Gazzaniga; Human, 307)

Prosopagnosia, a selective deficit in recognizing faces, is associated with damage to the occipitotemporal cortex, including the fusiform gyrus. (Squire; Fundamental Neuroscience, 1223)

Faces -- cortical representation appears to be relatively circumscribedObjects -- represented by a distributed pattern of activity across a broad expanse of ventral temporal cortex. (Squire; Fundamental Neuroscience, 1224)


             Link to — Neuron Response to Faces

             Link to — Face Recognition in Distant Taxa


Hippocampal System

Hippocampal system contains afferents from all sensory modalities, which may be better conceived as functionally rather than perceptually defined inputs. Cortical areas that project to the hippocampal system contain multimodal information that defines the meaning of a stimulus according to functional designations of cortical modules. (Eichenbaum; Olfactory Perception and Memory, 192)

Different forms of binding of perceptual elements by components of the hippocampal system. (Eichenbaum; Olfactory Perception and Memory, 198)

Limbic System Categorization

Cortex is concerned with the categorization of the world; limbic system is concerned with value. (Edelman; Bright Air, 118)

Convergence Zones and Association Cortices

Convergence zones throughout association cortices and subcortical nuclei. (Damasio; Making Images, 21)

Rhinal areas, convergence zones, integrate information across sensory modalities, mental representations go beyond perceptions to become conceptions. (LeDoux; Synaptic Self, 104)

Association cortices do not process any one type of sensory information; rather, they receive inputs from a number of primary and secondary sensory cortices and associated thalamic nuclei. (Purves; Neuroscience, 418)

Vision, audition, and somatosensation merge in temporal and parietal association areas of the neocortex well before the common paths into the entorhinal cortex, amygdala, and prefrontal convergence sites. (Eichenbaum; Olfactory Perception and Memory, 180)

Common processing of conventional sensory modalities includes a convergence in the verbal areas of the neocortex. (Eichenbaum; Olfactory Perception and Memory, 180)

Pattern Theory

Pattern theory says that tightly coupled cortical areas seek, via some kind of relaxation functionality, to arrive at a mutual agreement in which lower areas' specific data form a fit with known, more abstract categorizations stored in higher areas' memory of prior activity. (Mumford; Neuronal Architectures, 135)

Bottom-up assertions of facts have to be included along with top-down memories of expected patterns. (Mumford; Neuronal Architectures, 135)

Visual input is processed through a sequence of stages that includes edge detection, feature extraction of varying complexity, and normalization for size, position, and orientation. The resulting neural representation is then compared with memory objects. (Ullman; Sequence Seeking Counterstreams, 257)

An attractive model for mental object search and matching is to applying bidirectional methods, using both bottom-up and top-down processing. This counterstreams notion fits well with the 1-to-6 layered architecture of the cortex. (Ullman; Sequence Seeking Counterstreams, 258)


Nonlinear interpolation among stored orthographic or perspective views that can be determined on the basic of geometric features or material properties of the object. (Logothetis, Object Recognition in Primates, 147)

Visual Processing

In the visual system, early cortical processing stages detect specific features such as contrast, color, depth, and movement separately, and the representations of these features are systematically organized. (Eichenbaum; Olfactory Perception and Memory, 176)

The highest-level processing of the visual system, combining simpler features of perceptual objects, occurs in the inferotemporal area with its enormous convergence of inputs about visual features. At this stage of visual processing, no topography has been identified. (Eichenbaum; Olfactory Perception and Memory, 177)

In the inferotemporal area there is a clustering of cells involved in encoding particular stimuli. (Eichenbaum; Olfactory Perception and Memory, 178)

Perception of Three-Dimensional (3D) Structure

One of the most perplexing phenomena in the study of human perception is the ability of observers to determine the layout and three-dimensional (3D) structure of objects in the environment from the two-dimensional (2D) patterns of light that project onto the retina. (Tittle; Perception 3D Structure, 715)

Review various functional modules that have been proposed for analyzing an object's 3D structure from optical information, such a shading, texture, motion, and stereo. (Tittle; Perception 3D Structure, 715)

Functional models for integrating multiple sources of information about 3D structure include Bayesian models, which can account for nonlinear (i.e. facilitatory) interaction. (Tittle; Perception 3D Structure, 718)


Olfactory Perception and Memory

Taste can be simplified to four primitive chemical categories, and responses are monotonic to concentration. (Eichenbaum; Olfactory Perception and Memory, 177)

Instead of odor primitives, the olfactory system likely uses categorization mechanisms based on distributed olfactory cortical networks. (Eichenbaum; Olfactory Perception and Memory, 179)

Analysis of sensory processing by cell assemblies in the relatively simple olfactory cortex may offer insights into coding at higher levels in other sensory systems. . (Eichenbaum; Olfactory Perception and Memory, 179)

Continuous turnover of receptor cells occurs in the olfactory sensorium; receptor cells are gradually renewed. (Eichenbaum; Olfactory Perception and Memory, 179)

Olfactory bulb remains plastic beyond its full development; injury or odor deprivation can result in reorganization in the bulb well into adulthood. . (Eichenbaum; Olfactory Perception and Memory, 179)

Olfactory identification is very poor. (Eichenbaum; Olfactory Perception and Memory, 179)

Odor memories can be exceedingly powerful. A fragrant perfume can bring forth strong memories associated with a long-forgotten romance. (Eichenbaum; Olfactory Perception and Memory, 179)

Olfactory identification is very poor for humans; they often misidentify highly familiar odors using only olfactory cues. (Eichenbaum; Olfactory Perception and Memory, 179)

Odor processing does not converge with that of other senses until the final common paths into the entorhinal cortex, amygdala, and prefrontal area. (Eichenbaum; Olfactory Perception and Memory, 180)

Vision, audition, and somatosensation merge in temporal and parietal association areas of the neocortex well before the common paths into the entorhinal cortex, amygdala, and prefrontal convergence sites. (Eichenbaum; Olfactory Perception and Memory, 180)

Common processing of conventional sensory modalities includes a convergence in the verbal areas of the neocortex. (Eichenbaum; Olfactory Perception and Memory, 180)


Research study — Perceptual Categorization -- Recent Research



    Link to — Consciousness Subject Outline

    Further discussion — Covington Theory of Consciousness