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

Covington Theory of Consciousness

I’ll lay out here my theory of consciousness based upon my understanding of statements made by experts.

(It’s best to start at my title page — Scientific Understanding of Consciousness)

 

In a separate page, I review some of the significant contributions to my understanding of consciousness.

Evolution of Brain Structure and Function

The brain's evolution over millions of years has resulted in a three-level modularity of (1) brainstem structures, (2) limbic system structures, and (3) neocortex and attendant subcortical structures. The brainstem functions to provide gross stability and unconscious support for neural operations. The limbic system provides evolution-engraved quick responses for external encounters. The neocortex provides culturally-refined responses that constrain the extremes of the limbic system.

Consciousness -- an Emergent Property of Neuronal Network Activity

Consciousness is an emergent property of neuronal network activity in the brain.

Consciousness is spatially multiple yet effectively single at any one time.  It is an emergent property of noncommitted and divergent groups of neurons (gestalts) that is continuously variable with respect to and always entailing a stimulus epicenter. (Greenfield; Centers of Mind, 97)

Consciousness is the sustained, synchronized ~40 Hz electrical oscillation among the brain circuits. (Ratey; User's Guide to Brain, 136)

Brains can have consciousness as an emergent property. (Searle; Mystery of Consciousness, 13)

Consciousness is an emergent property arising from the self-organization of concurrently active but spatially distributed regions of the brain; there is no central organizer and no unique location where it comes into existence. (Johnston; Why We Feel, 124)

Consciousness is an emergent property that depends upon activity within large neural gestalts (dynamic core), whose size is regulated by arousal. (Johnston; Why We Feel, 124)

Scientific meaning of emergent -  The whole may not be the simple sum of the separate parts. The whole can be understood from (1)  behavior of the parts plus (2) knowledge of how all the parts interact. (Crick; Astonishing Hypothesis, 11)

Allan Hobson has stated some Building Blocks of Consciousness.

 

Network of Neurons Interconnected via Synapses

Projection neurons and interneurons are major players in the neuronal network. Synaptic connection is via chemical neurotransmitters. Most of the rapid synaptic communication is via glutamate for excitation by projection neurons and via GABA for inhibition by interneurons.  Modulatory neurotransmitters, using their own special receptors, influence the excitability of neurons.

Projection neurons have dendritic trees of ~104 synapses. Interneurons, mostly local, interconnect dendritic trees of projection neurons.

Networks of local interneurons, and the plasticity of synaptic connections with projection neurons, dynamically establish the activity of efficacious synapses for synaptically-connected, dynamic neuronal patterns.

Patterns of neural signal traces in the dendritic trees of neurons, dynamically connected momentarily by efficacious synapses, sculptured by genetics and experience, mediate neural network activity, an ever-changing subset of which forms the dynamic core of consciousness.

The basic modular unit of the neocortex is a minicolumn, a vertically oriented cord of cells containing about 110 cells in a cylinder about 30 µm in diameter. The human brain contains about 600 million minicolumns. (Mouthcastle; Organizing Cerebral Function, 37)

 

Complexity of the neural network is indicated by the diffusion tensor image of the human brain obtained from 3-tesla MRI sequences.

 

Autism as a way to Probe the Synaptically Connected Network

Link to — Autism Spectrum Disorder

 

Human-type Consciousness

Human-type consciousness is mediated by a greatly expanded brain facility compared with other animals. Most prominent among these is a greatly expanded frontal cortex and the uniquely human Broca and Wernicke language areas. The hugely expanded frontal cortex, facilitating cognitive reasoning, thinking, planning and decision making has coevolved with the special language areas. Human-type consciousness is dependent upon the function of Core Consciousness.

 Core Consciousness

Core consciousness is a "convolution" of a mental image with the sense of self.

Primary consciousness (Core Consciousness) comprises sensation, perception, emotion, learning, geographic orientation, instinct, primary intention; all of these can be operationally defined in lower animals.  (Hobson; Consciousness, 84)

The terms primary/secondary, core/extended, core/human-type have been used to describe human consciousness as distinguished from the consciousness experience by animals. Here are paraphrases from Allan Hobson:

Primary components of consciousness are those experienced by all mammals, including human infants: sensation, perception, attention, emotion, instinct, movement. (Hobson; Consciousness, 16)

Secondary components of consciousness are those experienced only by adult humans: memory, thought, language, intention, orientation, volition. (Hobson; Consciousness, 17)

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

Consciousness is a ‘convolution’ (my choice of word; it's hard to precisely convey the concept) of a current mental image with a neural network image of the self. The result is what Edelman calls the “remembered present” of consciousness.

This link will give my interpretation of Edelman's core consciousness:

 

 

 

 

 

 

 

 

 

The Self and the Sense-of-Self

The self is a person’s neural representation by the entire ensemble of CNS neurons along with the neuronal network connectivity pattern of synaptic efficacies established by genetics together with lifelong experience in the natural and social environment.

Sense-of-self is the basis of consciousnessSense-of-self is a neural activity pattern associated with a current perception or thought. The sense-of-self will include unconscious neural activity as well as conscious activity.

The interaction of the neural network activity of a current mental image together with the neural network activity representing the self constitutes what Edelman calls the “remembered present” of consciousness.

The interaction of this current mental image neural network activity with the self neural network activity occurs in the dynamic core of the thalamocortical system.

Orientation

Consciousness includes implicit functions of orientation in time, space, and self-representation such as sexual orientation.  Orientation constantly provides implicit understanding of: Who am I?, Where am I?, What time of day is it?, What year is it?,

The parietal lobe appears to be most important for bodily awareness and awareness of space. (Revonsuo; Inner Presence, 312)

Recency effect is what allows us to orient ourselves in time and space. (Baddeley; Working Memory, 115)

Ability to discriminate amongst our memories becomes less as the delay increases. (Baddeley; Working Memory, 106)

Recency effect is one of the most stable and reliable phenomena within the study of human memory. (Baddeley; Working Memory, 115)

A person's sexual orientation is an essential ingredient of the Self. My current belief is that sexual orientation is established during prenatal neural network development.

Mental image

Mental images are the mental constructs we normally experience in consciousness. Neural patterns or neural maps or maps are the neural representation of the mental images.

Perception, Memory, Consciousness

Perception, memory, and consciousness are closely intertwined.  The basis for consciousness is "the self" comprised of the entire ensemble of neurons and their synaptic connection efficacies laid out by genetics and continually modified via neuronal plasticity through a lifetime of experience and interactions with the environment. A perception is the activation by a sensory input pattern of a neural subnetwork pattern within the self. A memory is the reactivation (or more accurately “reconstruction”) of a past perception.

Synaptic plasticity with attendant (consolidation/fading) establishes a lingering perception as memory.

Neurocomputational models

Neurocomputational models enable the single neuron level of analysis to be linked to the level of large-scale neuronal networks and the interactions between them, so that large-scale processes such as memory retrieval, object recognition, attention, and decision-making can be understood. (Rolls; Memory, Attention, and Decision-Making, 3)

The metaphor of "object-oriented programming" may be helpful.  I believe there are many thousands of tiny local functional modules operating in parallel and hierarchically with recurrent and reentrant connections operating recursively.  This brings to mind object oriented programming, which is used in a number of modern programming languages.

Neuron assemblies

Basic unit of the selective process is not the individual neurons but the neuronal group. (Ratey; User's Guide to Brain, 142)

There are perhaps 100 million neuronal groups in the brain, and they range in size from 50 to 10,000 neurons. (Ratey; User's Guide to Brain, 142)

Because single neurons have small and uncertain effects on other neurons, the cortical description must be carried out in terms of stochastic neuronal populations rather than at the level of individual cells.

Neurons are only effective in groups, working toward a single goal, such as discriminating color or producing emotion. (Ratey; User's Guide to Brain, 142)

By virtue of their size, neuronal groups can compensate for individual cell deaths. (Ratey; User's Guide to Brain, 142)

Brain' s Three Topological Networks

The brain has three topological networks: (1) thalamocortical system, (2) parallel system through basal ganglia, cerebellum, and thalamus, (3) diffusely projecting modulatory neurons from the brainstem and midbrain.

Thalamocortical System

Intralamina nuclei of the thalamus receive and project long axons to many areas of the brain. Information flowing back and forth between the intralamina nuclei of the thalamus and the rest of the brain modulates itself, setting up a regular loop of electrical activity oscillating to a synchronized beat of ~40 Hz. This thalamocortical system of reentrant neuronal activity contains a dynamic core subnetwork that mediates consciousness. During waking there are large burst of electrical activity in every brain region, in addition to the steady 40 Hz oscillation. During non-dreaming sleep, the intralaminar nuclei are inactive; there is no 40 Hz oscillation. During dream sleep (REM sleep), the 40 Hz background oscillation returns, and is again accompanied by heavy regional activity, similar to that which occurs during waking.

Reentrant activity leading to recursion is a fundamental feature of thalamocortical activity, and indeed nearly all neural activity.  Reentrant activity is not simple feedback but functions in a network as recursive multiple pathways, which update cyclically on a time scale of tens to hundreds of milliseconds, rapidly converging to the dynamic core’s synaptically connected neuronal network mediating an instantaneous thought. This cyclical neural activity generates gamma (~40-Hz) oscillations in the normal waking state.

Research experiments indicate that humans perform near-optimal Bayesian inference in a wide variety of tasks, ranging from cue integration to decision making to motor control. This implies that neurons both represent probability distributions and combine those distributions according to a close approximation to Bayes' rule.

Parallel System through Basal Ganglia, Cerebellum, and Thalamus

A set of parallel, unidirectional chains link the cortex to a set of its appendages, each with a special structure -- the cerebellum, the basal ganglia, and the hippocampus. (Edelman; Universe of Consciousness, 45)

Nearly all regions of the neocortex project directly to the striatum, making the cerebral cortex the source of the largest input to the basal ganglia, by far. (Purves; Neuroscience, 418)

Of the cortical areas that innervate the striatum, the heaviest projections are from association areas in the frontal and parietal lobes, but substantial contributions also arise from the temporal, insular, and cingulate cortices. (Purves; Neuroscience, 418)

The fact that different cortical areas project to different regions of the striatum implies that the corticostriatal pathway consists of multiple parallel pathways serving different functions. (Purves; Neuroscience, 419)

Efferent neurons of the internal globus pallidus and substantia nigra pars reticulata together give rise to the major pathways that link the basal ganglia with upper motor neurons located in the cortex and in the brainstem. (Purves; Neuroscience, 423)

Diffusely Projecting Modulatory Neurons

Fan-out meshworks of diffusely projecting neuromodulatory neurons emanate from brain stem and midbrain nuclei. Reentrant circuits of the thalamocortical system are modulated by these neurotransmitters.

Modulatory neurotransmitters, operating in seconds, minutes or longer, often emanate from widely-projecting neurons clustered in sub-cortical ganglia. Chemical and functional changes in the synapses of neurons provide many of the short-term and longer-term changes such as memory in the brain function of neural networks.

Major modulatory systems of the brain. (1) noradrenergic, (2) adrenergic, (3) dopaminergic, (4) serotonergic, (5) cholinergic, (6) histaminergic. (Kandel; Principles of Neural Science, 890)

Small collections of neurons can deliver a dose of dopamine, norepinephrine, serotonin or acetylcholine to widespread regions of the brain including the cerebral cortex and basal ganglia.

Dopaminergic neurons send their axons to the nucleus accumbens, the striatum, and the frontal cortex, three structures thought to be involved in motivation.

Dynamic core

The Dynamic Core hypothesis formulated by Gerald Edelman is the fundamental neurobiological foundation of my concept of consciousness. The dynamic core is a constantly changing hierarchical web of reentrant neural activity (perhaps <5% of total neural activity at any one instant) that mediates a mental pattern of thought at any one instant. The mental pattern supported by the dynamic core can be a thought pattern during the waking state, or it can be the thought pattern during the dreaming state. The thalamocortical activity begins prenatally and continues uninterrupted until death or until an abnormal state such as brain death.

Link to — Dynamic Core triggers Associated Memories

 

Gestalts

Most scholars emphasize how the collective Gestalt-like traits of the brain and its networks are critical to understanding consciousness.  (Koch; Quest for Consciousness, 311)

My speculation is that neuronal assemblies in the brain mediate hierarchies of gestalts bound in coherence momentarily by rentry and recursion and by the associative property of memory to produce the Dynamic Core of consciousness in the thalamocortical system.

Gestalts were postulated by German psychologists early in the 20th century to account for the way the mind seems to combine visual patterns into perceptions. In later research, continuing with Donald Hebb in 1949 and with recent research in neuroscience, neuronal assemblies with recurrent functionality and autoassociative functionality have been hypothesized to account for the associative properties of memory.

I will discuss Gestalts with the implication that they are mediated by neuronal assemblies of recurrent and autoassociative circuitry. The detailed neuronal circuitry formation of gestalts is likely mediated via Spreading Activation.

Consciousness is an emergent property of nonspecialized and divergent groups of neurons (gestalts) that is continuously variable with respect to, and always entailing, a stimulus epicenter. Size of the gestalt, and hence the depth of prevailing consciousness, is the product of the interaction between the recruiting strength of the epicenter and the degree of arousal. (Greenfield; Centers of Mind, 104)

Hierarchy of Gestalts

The enormous associative capabilities of the dynamic core are ideal to link or hierarchically organize a series of preexisting unconscious routines into a particular sequence. (Edelman; Universe of Consciousness, 187)

The network hierarchy is a fractal network hierarchy characterized by the complexity property of 1/f distribution of "pink noise." This distribution can be detected in the power spectrum of the EEG.

The amplitude of the EEG power spectrum increases as the frequency decreases.  This inverse relationship is expressed as the "one over f" power spectrum (also called "pink" noise). (Buzsáki; Rhythms of the Brain, 119)

Dynamically self-assembled layers of asynchronous local recurrent neural assemblies coagulate active network assemblies into the dynamic core, characterized by sparsity in a widely distributed active network.

Coherent Binding of Gestalts

A group of neurons can contribute directly to conscious experience only if it is part of a distributed functional cluster that, through reentrant interactions in the thalamocortical system, achieves high integration in hundreds of milliseconds. (Edelman; Universe of Consciousness, 144)

The associative property of memory, using the attractor state of neural networks, many with a local short-term memory, coherently agglomerate widely distributed neural assemblies into the dynamic core.

Autoassociative networks can recall the appropriate memory from the network when provided with a fragment of one of the memories. (Rolls; Memory, Attention, and Decision-Making, 560)

The neural network operates asynchronously. A projection neuron, with its dendritic tree of ~104 synapses, fires when a quorum of input signals momentarily exceeds its threshold. The neuron's signal joins millions of other neuronal signals circulating in the network via the most efficacious synapses.

Asynchronous Local Circuits, Coherent Neuronal Assemblies, Power Specturm of EEG

Local circuits tend to operate asynchronously. They are drawn into coherence by the associative property of memory.

The neural network likely functions as a nested hierarchy of recursive loops operating at perhaps ~20 ms for visual sensory circuits, maybe ~50 ms in association cortex areas for perception, and perhaps >1 second for decision circuits in frontal cortex.

There is considerable evidence that the processing time required in each cortical area for useful computation is of the order of 20-30 ms. (Rolls & Treves; Neural Networks, 177)

By the associative property of memory, neural assemblies aggregate via the laws of Gestalts into the sparse but widespread neural assemblies of the dynamic core of consciousness.

The enormous associative capabilities of the dynamic core are ideal to link or hierarchically organize a series of preexisting unconscious routines into a particular sequence. (Edelman; Universe of Consciousness, 187)

Orderings of computations is necessary for performance. Ordering does not take place by a strict serial organization. Instead, computations pass information back and forth to coordinate their results. (Posner; Constructing Neuronal Theories of Mind, 198)

These recursive guidance computations can comprise a complex system organized at multiple timescales. Slow rhythms involve very large numbers of cells that can be "heard" over a long distance, whereas localized fast oscillations involving only a small fraction of neurons may be conveyed only to a few partners. Power spectrum of the EEG is a straight line on a log-log plot, showing amplitude increasing as frequency decreases.  This inverse relationship is expressed as the "one over f" power spectrum (also called "pink" noise). (Buzsáki - Rhythms of the Brain, 119)

Minimal Functionality Of Consciousness

At the current state of science, the minimal functionality required for consciousness is currently unknown.  There is much uncertainty in borderline areas such as Persistent Vegetative State.

Attention and Consciousness

Attention is necessary for consciousness. (Baddeley; Working Memory, 311)

In the real world, multiple streams of information reach our awareness, some of it relevant, some not for the task at hand. With the inherent capacity limitations of working memory, it is essential that only representations of task-relevant information are generated and maintained. An important aspect of goal-directed behavior is understanding the neural mechanisms underlying how task-relevant versus task-irrelevant information is differentially processed. (Gazzaley; Top-down WM, 197)

The brains of complex organisms are threatened with information overload.  In primates, about one million nerve fibers leave each eye and carry on the order of 1 MB per second of raw information. The brain' s attention mechanisms function to select the information of current relevance to the organism.

Key brain structure involved in attention is the thalamus, a large collection of cells located atop the brainstem in the center of the upper brain. (Hobson; Consciousness, 59)

Vigilance—or sustained attention—ensures that goals are maintained over time. (Parasuraman; Attentive Brain, 7)

Four main projection systems have been identified as playing functional roles in arousal and attention: (1) cholinergic basal forebrain, (2) noradrenergic nucleus locus coerulus (LC), (3) dopaminergic median forebrain bundle, (4) serotonergic dorsal raphe nucleus. (Parasuraman; Varieties of Attention, 227)

Pulse-like behavior of neurons and the neural network

Thousands of synapses on dendrites comprise the input terminals of a neuron. Thousands of other neurons and their axons form synapses with these dendrites. Some of these input axons are excitatory, some are inhibitory, and some are modulatory. The neural signals incoming to the receptors are brief (a millisecond or so) and must be considered as pulses. If the summation of these incoming pulses momentarily exceeds the neuron’s quorum threshold at the neuron’s soma, the neuron will “fire” a signal down its axon. A quorum is any combination of synaptic inputs in a ~2 ms time window that causes the neuron's axon hillock to exceed threshold; no particular synapses are required.

Dendritic trees contain spines, which may function to provide highly effective and modifiable chemical and electrical compartments that regulate synaptic efficacy, integration and plasticity.

Stochastic nature of neuronal behavior

An individual neuron does not fire in a deterministic fashion. The thousands of synaptic inputs on the dendritic tree of a neuron function on a quorum population basis to result in a probabilistic influence on the neuron’s firing.

Because single neurons have small and uncertain effects on other neurons, the cortical description must be carried out in terms of neuronal populations rather than at the level of individual cells. (Stevens; Cortical Theory, 242)

The overall stochastic nature of neuronal behavior suggests that the physiologically meaningful signal from cortex should be the average firing rates of a population of perhaps 100 to 1000 neurons near a particular cortical site. (Stevens; Cortical Theory, 243)

Reentry and Recursion

The brain's neural network has a neuronal network model of reality for predicting changes in its situation and commanding optimal action. The neuronal network uses reentry and recursion to update and refresh this internal model on the basis of about ~100 ms.

A metaphor of weather forecasting may be helpful. Weather forecasters have a computer model of weather patterns, which they update continually with atmospheric data. The computer model produces forecasts for the near-term future, allowing people to plan their activities. In a similar way, the brain's neuronal network uses sensory input data to update its internal model of reality for prediction and optimal control of behavior. Much of this neural activity proceeds unconsciously. In friendly conversation, for example, a person's neuronal network is continuously active in sensory and language areas and in areas invoking the hierarchy of muscular movement patterns for vocal speech.

Nested hierarchy of reentry and recursion

The neural network likely functions as a nested hierarchy of recursive loops operating at perhaps ~20 ms for visual sensory circuits, maybe ~50 ms in association cortex areas for perception, and perhaps >1 second for decision circuits in frontal cortex. Within sensory circuits, the network likely uses Spreading Activation to maintain response within 20 ms.

There is considerable evidence that the processing time required in each cortical area for useful computation is of the order of 20-30 ms. (Rolls & Treves; Neural Networks, 177)

A metaphor may be helpful. My experience with the Apollo lunar guidance system in the 1960s may have some insightful parallels for the brain's neural circuitry. The lunar ascent guidance system had gyroscopes and accelerometers whose rapidly changing state variables were refreshed every 10 ms. The vehicle attitude orientation computations were refreshed every 20 ms, and the vehicle guidance equations of position and velocity were refreshed every 2 seconds. This hierarchy of computations provided rapid response for rapidly changing quantities but allowed more time for more complex, slowly changing quantities.

This nested hierarchy of recursive guidance computations may provide some insight for the neural circuitry in the brain. I suspect the visual sensory cortex operates on perhaps a ~20 ms recursive cycle, the multimodal association cortex on perhaps a ~50 ms cycle, and the frontal cortex, with back projections to the posterior cortical areas, may operate on a >1 second recursive cycle.

Bayesian Inference

Psychophysical experiments indicate that humans perform near-optimal Bayesian inference in a wide variety of tasks, ranging from cue integration to decision making to motor control. (“Bayesian Inference in Brain Functionality,” Nature Neuroscience, published online 22 October 2006)

Bayesian statistics is such a powerful and versatile concept that we should expect the neural networks to use it in a large range of circumstances. (Doya, et al.; Bayesian Brain, 305)

Research studies have shown that people's behavior is well predicted by the assumption that they use optimal Bayesian statistics as a strategy. (Doya, et al.; Bayesian Brain, 305)

Sensory Systems

Within each modality, sensory inputs are processed by activity in a constellation of cortical regions that analyze specific aspects of the stimuli to continuously update the dynamic neuronal network model of reality. (Llinás & Paré; Brain Modulated by Senses, 5)

Dreamlike state modulated by the senses

Dreaming and wakefulness are so similar from electrophysiological and neurological points of view that wakefulness may be described as a dreamlike state modulated by sensory input. (Llinás & Paré; Brain Modulated by Senses, 6)

Imagery and emotions of dreams are always with us, riding in our nonconscious, and we change state from waking to dreaming, this information is able to cross into consciousness. (Hobson; Dreaming as Delirium, 209)

Brain Functions as a Reality Emulator

The brain functions as a reality emulator to assist the animal with prediction and decisions to enhance survival.  In this process the brain performs near-optimal Bayesian inference to continuously update its dynamic neuronal network model of reality with the stream of input data from the senses.

Brain operates as a reality emulator. (Llinás; I of the Vortex, 13)

The brain constructs an explicit, multilevel, symbolic interpretation of parts of its environment.  (Koch and Crick; Neuronal Basis, 109)

The brain fashions an internal model of the external world as a basis for prediction and exploration of alternatives. (e.g., mental exploration of possible move sequences in chess)   (Holland; Hidden Order, 33)

Brain is a system whose processes create states of consciousness in response not only to sensory inputs but also to internal signals representing expectations based on past experiences.  (Logothetis; Window on Consciousness, 89)

Perception-action cycle is the circular processing of information between posterior and frontal cortices in the integration of sensory -- motor behavior, as well is in higher cognitive activities such as language. (Fuster; Cortex and Mind, 218)

Declarative memory functions to represent objects and events in the external world and the relationships between them.  (Squire & Kandel; Memory, 99)

The illusion of the brain's reality emulator is so powerful and ubiquitous that we come to believe that objects really are red, or hot, or bitter, or sweet, or beautiful, and we usually do not ask how or why we impose this structure on our physical world, or how the structure relates to our biological survival. (Johnston; Why We Feel, 13)

Brain Can Misinterpret Sensory Input Data

Unfortunately, the brain can misinterpret sensory input data and conjure internal models that do not correspond to reality.

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)

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)

Humor is what happens when an assumption is epistemically committed to in a mental space and then discovered to have been a mistake. (Hurley, Dennett, Adams; Inside Jokes, 121)

 

Memory Is Necessary for Consciousness

Memory is a central component of the brain mechanisms that lead to consciousness. (Edelman; Universe of Consciousness, 93)

Memory is not a single entity but is composed of different systems.  Only one of these systems is accessible to awareness, the declarative memory system. (Squire & Kandel; Memory, 159)

Cognitive psychologists subdivide short-term memory into two major components: immediate memory and working memory. (Squire & Kandel; Memory, 84)

Memory -- Declarative, Procedural, Emotional

Three major memory systems in the brain. (Eichenbaum; Neuroscience of Memory, 200)

Hippocampus and Memory

The hippocampus is required for forming new declarative memories. It is not required for procedural memory. The hippocampus is required for recalling new declarative memories before their consolidation as long-term memories. The consolidation process begins with emotional influence and rehearsal during waketime and continues during sleep and dreaming, resulting after days or weeks in long-term memories that can be reconstructed independently of the hippocampus.

Associative Property of Memory

All memory is associative. Memory recall is a reactivation (reconstruction) of an original neuronal pattern of perception triggered by an activated-cue fragment of the original neuronal pattern.

Procedural Memory

Nested hierarchies of motor command procedures, variously called Central Pattern Generators (CPGs) or Fixed Action Patterns (FAPs) or Dispositions, emanating from the basal ganglia, premotor cortex, motor cortex, brain stem and spinal cord produce movement patterns unconsciously. The nested hierarchies of motor commands include those that were acquired innately, together with the many that have been learned since infancy. These FAPs range from the vocal muscular patterns of speech, to the skills of riding a bicycle, playing a piano, and various sports activities.

Working Memory

Working memory is a momentary network-assembly of neurons, principally in the frontal cortex, that interact with most other modular areas of the brain to perform the higher levels of sensory processing, to arrive at decisions, and to produce commands for movement. Working memory is intimately related to the ongoing neural activity of the thalamocortical system. The memory function of working memory may be located in the widely distributed synapses in the brain, with principal control-functions in the frontal cortex and the thalamocortical system (diagram).

Working memory, the dynamic core, and the thalamocortical system are intimately related as the mediators of consciousness.

Working memory is one of the brain's most sophisticated capacities and is involved in all aspects of thinking and problem-solving. (LeDoux; Synaptic Self, 175)

Consciousness serves as a mental workspace, a very powerful mechanism for registering the environment and relating it to past experience, which can in turn be used to model the present, and using that model, to simulate and hence to predict the future and plan further action. (Baddeley; Working Memory, 314)

Working memory includes: (1) the central executive, (2) the phonological loop, (3) the visuospatial sketchpad, and (4) the episodic buffer.  Working memory functions of the frontal cortex interact with the parietal and temporal cortex, along with subcortical areas such as the basal ganglia and limbic system. Working memory and the thalamocortical system are closely related to consciousness.

Activated Long-Term memory can constitute a form of Working Memory

The Central Executive of Working Memory can send activation bias signals into long-term memory in the posterior cortical areas. The bias signals can activate memory neural assemblies in sensory association cortex together with synaptic efficacies representing the Self.

Short-term retention of information in working memory is supported by sustained activity in cortical regions whose primary function is not working memory. (Postle; Activated Long-Term Memory, 344)

 

Pain  -- -- Pleasure

All feelings contain some aspect of pain or pleasure as a necessary ingredient. (Damasio; Looking for Spinoza, 123)

Pleasure is a key factor in controlling the motivated behavior of humans. (Kandel; Principles of Neural Science, 1007)

Amygdala and Fear

The ancient mechanisms of fear via the amygdala together with the olfactory system permit rapid response for movement control.

Amygdala and its connections to the prefrontal cortex and basal ganglia are likely to influence the selection and initiation of behaviors aimed at obtaining rewards and avoiding punishments. (Purves; Neuroscience, 701)

Pleasure Pathway

Stimulation of the nucleus accumbens in humans elicits smiling, laughter, pleasurable feelings, happiness, even euphoria. (Cardoso; Hardwired for Happiness, 173)

      Nucleus Accumbens Pleasure Center of the Brain

 

Emotion, Cognition, Motivation

The limbic system provides hedonic signals, which function to guide, often in a dominant way, the cognitive decision process.

Emotion and motivation are linked by the property that both involve rewards and punishers. (Rolls; Emotion Explained, 1)

Emotion

Emotions are among the very oldest of the brain's properties. Limbic system, hypothalamus, and brain stem intervene in body regulation and in all neural processes on which mind phenomena are based. Emotions are linked to the motor aspects of FAPs by access through the amygdala and the hypothalamus and their connectivity with the brain stem.

 The limbic system consists of a number of subcortical structures, which are active in emotions and which are tightly interrelated with cortical functions.  In recent years, some neuroscientists have included the prefrontal cortex as a member of the limbic system, since it is often heavily involved in emotional activity.

Emotion and Music

Trying to understand the brain's neural mechanism for music is probably a good approach to gain an enhanced understanding of emotion.

The rewarding and reinforcing aspects of listening to music seem to be mediated by increasing dopamine levels in the nucleus accumbens and by the cerebellum's contribution to regulating emotion through its connections to the frontal lobe and the limbic system. (Levitin; Your Brain on Music, 187)

The music faculty is not a monolithic entity that a person either has or does not. Rather, it comprises a set of neurally isolable processing components, each having the potential to be specialized for music. Researchers have proposed a functional architecture for music processing that captures the typical properties of modular organization.

Basic Emotions

Although there is no consensus among experts, six so-called primary or universal emotions are often stated, for example: Happiness, Sadness, Fear, Anger, Surprise, Disgust.

Eight basic emotions: surprise, interest, joy, rage, fear, disgust, shame, anguish - controlled by 'hardwired' brain systems. (LeDoux; Emotional Brain, 112)

Secondary Emotions

Many secondary emotions could be proposed, such as the social emotion ‘embarrassment,’ although I don't think it's helpful to haggle over these possibilities.

We often evaluate the self and others from social comparisons. We feel envy when the target person has superior and self-relevant characteristics. Schadenfreude occurs when envied persons fall from grace.

Feelings

Conscious experiences of emotions -- the feelings. (LeDoux; Emotional Brain, 82)

A feeling is the perception of a certain state of the body along with the perception of a certain mode of thinking and of thoughts with certain themes. (Damasio; Looking for Spinoza, 86)

Higher order consciousness leads to a rich cognitive, affective, and imaginative domain -- feelings (qualia), thought, emotions, self-awareness, will, and imagination. (Edelman; Bright Air, 198)

Normal consciousness can take stock of emotions in the form of feelings, feelings can generate a new line of emotions that confers behavior. (Damasio; Feeling of What Happens, 101)

Conscious experiences, like sensations and feelings, evolved because they dictated a dynamic organization of the nervous system that could prioritize experiences and distinguish between environmental events or circumstances that had a real influence on biological survival. (Johnston; Why We Feel, 127)

Why do we have so many different feelings, like love, pride, fear, and sadness?  All such feelings are evolved "omens" of our reproductive success that amplify the consequences of physical and social events that have some bearing on our gene survival. (Johnston; Why We Feel, viii)

Consciousness, in the form of working memory, has become an important part of the way LeDoux thinks about emotions, especially feelings. (LeDoux; Synaptic Self, 199)

Cognition

Ability to solve spatial problems efficiently is special, apart from straight logical or linguistic ability. (Gardner; Frames of Mind, 175)

One reason human cognition is so powerful is because we have language in our brains, which exponentially increases the ability to categorize information. (LeDoux; Synaptic Self, 177)

The emergence of cognitive capacities underlying language changed the way the brain works, making it possible for human brains to think and experience events in ways that other brains cannot. (LeDoux; Synaptic Self, 198)

Cognition and Humor

Trying to understand the brain's neural mechanism for humor is probably a good approach to gain an enhanced understanding of cognition.

Basic humor is any semantic circumstance in which we make a mistake in active belief structures and succeed in discovering the mistake. (Hurley, Dennett, Adams; Inside Jokes, 117)

Multiple Intelligences

Humans have great variety in their mental capabilities involving multiple intelligences; a few examples: (1) rapid, vivid conceptualization; (2) spatial visualization of geometrical objects; (3) mathematical, logical, analytical reasoning; (4) facility with mental arithmetic; (5) facility with language; (6) poetic creativity; (7) musical creativity; (8) artistic creativity; (9) expansive memory; etc. Theory of multiple intelligences was developed in 1983 by Howard Gardner, professor of education at Harvard University.

Motivation

Cingulate gyrus is the main link between motivation and emotion. (Ratey; User's Guide to Brain, 248)

When motivation is based on decisions, the prefrontal cortex will be involved. (LeDoux; Synaptic Self, 252)

Motivation circuits include the hippocampus by way of its connections with the amygdala and accumbens. (LeDoux; Synaptic Self, 251)

 Movement control

Movement is nearly always the functional result of wake-time brain activity.  Movement is facilitated in the brain and nervous system by a hierarchy of modular functionality I call FAPs, but known by a number of names.

Voluntary movement requires the coordinated activity of all complements of the motor system including the motor cortex, basal ganglia, thalamus, midbrain, cerebellum, and spinal cord.

Startle Response

Basic reflexes include the startle reflex, which organisms deploy in reaction to a noise or touch, or as the tropisms that guide organisms from extreme heat or extreme cold, or the way from dark into light. (Damasio; Looking for Spinoza, 31)

Primary acoustic startle reflex is controlled by brainstem nuclei. (Robbins; Pharmacology, Arousal, Attention, 208)

As the result of sensitization, when we encounter a fearful stimulus, such as a loud noise, we become for some time more likely to startle, or startle more vigorously. (Eichenbaum; Neuroscience of Memory, 43)

Sleep and Dreaming

Allan Hobson’s AIM Sleep Model

Sleep Stages Diagram

 

Modularity of Brain

Consciousness is mediated by widespread neural activity in many of the modular areas of the brain. Consciousness is an emergent property of the cortical activity that mediates a particular momentary thought, and since thoughts are fleeting from moment to moment, the subset of neural activity for thoughts changes on a momentary basis. The dynamic core of consciousness neural activity is focused in the thalamocortical system (thalamus and cortex reentrant circuits) but also includes working memory (frontal cortex with its subdivisions), emotional functionality of the limbic system, basal ganglia, cerebellum and other subcortical areas controlling movement, and the modulator areas of the brain stem.

 

 

A very significant paper on consciousness – Giulio Tononi and Gerald Edelman, in my opinion, authored a very significant paper on the scientific principles of consciousness.  However, it can seem very arcane, so I have rendered my paraphrase version which should provide the gist of their thought in a form much more readable and understandable.

 

Further Research is Needed

Music, art, sleep, sex, and love are experience sources that, if properly understood in terms of neural network functionality, could greatly elucidate the understanding of consciousness.

 

 

Return to — Scientific Understanding of Consciousness

Link to — Consciousness Subject Outline

Link to — ‘Scatter of Topics’ Diagrams