Metastability in the brain
Encyclopedia
In the field of computational neuroscience
, the theory of metastability refers to the human brain’s
ability to integrate several functional parts and to produce neural oscillations
in a cooperative and coordinated manner, providing the basis for conscious
activity.
Metastability, a state in which signals (such as oscillatory waves) fall outside their natural equilibrium state but persist for an extended period of time, is a principle that describes the brain’s ability to make sense out of seemingly random environmental cues. In the past 25 years, interest in metastability and the underlying framework of nonlinear dynamics has been fueled by advancements in the methods by which computers model brain activity.
measures the gross electrical activity of the brain that can be observed on the surface of the skull. In the metastability theory, EEG outputs produce oscillations that can be described as having identifiable patterns that correlate with each other at certain frequencies. Each neuron
in a neuronal network normally outputs a dynamical oscillatory waveform, but also has the ability to output a chaotic
waveform. When neurons are integrated into the neural network by interfacing neurons with each other, the dynamical oscillations created by each neuron can be combined to form highly predictable EEG oscillations.
By identifying these correlations and the individual neurons that contribute to predictable EEG oscillations, scientists can determine which cortical domains
are processing in parallel and which neuronal networks are intertwined. In many cases, metastability describes instances in which distal parts of the brain interact with each other to respond to environmental stimuli.
or chaotic signals into predictable oscillatory patterns.
In EEG oscillations of neural networks, neighboring waveform frequencies are correlated on a logarithmic scale
rather than a linear
scale. As a result, mean frequencies in oscillatory bands cannot link together according to linearity of their mean frequencies. Instead, phase transitions are linked according to their ability to couple with adjacent phase shifts in a constant state of transition between unstable and stable phase synchronization
. This phase synchronization forms the basis of metastable behavior in neural networks.
Metastable behavior occurs at the high frequency
domain known as 1/f regime
. This regime describes an environment in which a noisy signal (also known as pink noise
) has been induced, where the amount of power
the signal outputs over a certain bandwidth (its power spectral density) is inversely proportional to its frequency.
Noise at the 1/f regime can be found in many biological systems – for instance, in the output of a heartbeat in an ECG waveform—but serves a unique purpose for phase synchrony in neuronal networks. At the 1/f regime, the brain is in the critical state necessary for a conscious response to weak or chaotic environmental signals because it can shift the random signals into identifiable and predictable oscillatory waveforms. While often transient, these waveforms exist in a stable form long enough to contribute to what can be thought of as conscious response to environmental stimuli.
History of Coordination Dynamics and the Haken-Kelso
The so-named HKB model is one of the earliest and well-respected theories to describe coordination dynamics in the brain. In this model, the formation of neural networks can be partly described as self-organization
, where individual neurons and small neuronal systems aggregate and coordinate to either adapt or respond to local stimuli or to divide labor and specialize
in function.
In the last 20 years, the HKB model has become a widely-accepted theory to explain the coordinated movements and behaviors of individual neurons into large, end-to-end neural networks. Originally the model described a system in which spontaneous transitions observed in finger movements could be described as a series of in-phase and out-of-phase movements.
In the mid-1980s HKB model experiments, subjects were asked to wave one finger on each hand in two modes of direction: first, known as out of phase, both fingers moving in the same direction back and forth (as windshield wipers might move); and second, known as in-phase, where both fingers come together and move away to and from the midline of the body. To illustrate coordination dynamics, the subjects were asked to move their fingers out of phase with increasing speed until their fingers were moving as fast as possible. As movement approached its critical speed, the subjects’ fingers were found to move from out-of-phase (windshield-wiper-like) movement to in-phase (toward midline movement).
The HKB model, which has also been elucidated by several complex mathematical descriptors, is still a relatively simple but powerful way to describe seemingly-independent systems that come to reach synchrony just before a state of self-organized criticality
.
The traditional EEG is still useful to investigate coordination between different parts of the brain. 40 Hz gamma wave
activity is a prominent example of the brain’s ability to be modeled dynamically and is a common example of coordination dynamics. Continuous study of these and other oscillations has led to an important conclusion: analyzing waves as having a common signal phase but a different amplitude
leads to the possibility that these different signals serve a synergistic function.
It is interesting to note some unusual characteristics of these waves: they are virtually simultaneous and have a very short onset latency, which implies that they operate faster than synaptic conduction
would allow; and that their recognizable patterns are sometimes interrupted by periods of randomness
. The latter idiosyncrasy has served as the basis for assuming an interaction and transition between neural subsystems. Analysis of activation and deactivation of regions of the cortex has shown a dynamic shift between dependence and interdependence
, reflecting the brain’s metastable nature as a function of a coordinated dynamical system.
fMRI, large-scale electrode arrays
, and MEG
expand upon the patterns seen in EEG by providing visual confirmation of coordinated dynamics. The fMRI, which provides an improvement over EEG in spatiotemporal characterization, allows researchers to stimulate certain parts of the brain with environmental cues and observe the response in a holistic brain model
. Additionally, the fMRI has a response time of about one millisecond
, allowing for a virtually real-time investigation of the active turning –on and –off of selected parts of the brain in response to environmental cues and conscious tasks.
A new theory called the Phi complex
has been developed by J. A. Scott Kelso
and fellow researchers at Florida Atlantic University
to provide experimental results for the theory of social coordination dynamics. In Kelso's experiments, two subjects were separated by an opaque barrier and asked to wag their fingers; then the barrier was removed and the subjects were instructed to continue to wag their fingers as if no change had occurred. After a short period, the movements of the two subjects sometimes became coordinated and synchronized (but other times continued to be asynchronous). The link between EEG and conscious social interaction is described as Phi, one of several brain rhythms operating in the 10 Hz range. Phi consists of two components: one to favor solitary behavior and another to favor interactive (interpersonal) behavior. Further analysis of Phi may reveal the social and interpersonal implications of degenerative diseases such as schizophrenia
-- or may provide insight into common social relationships such as the dynamics of alpha and omega-males or the popular bystander effect
describing how people diffuse personal responsibility in emergency situations depending on the number of other individuals present.
interact in the form of synchronous oscillation. The interaction between distinct neuronal groups forms the dynamic core and may help explain the nature of conscious experience. A critical feature of the DCH is that instead of thinking binarily about transitions between neural integration and non-integration (i.e., that the two are either one or the other with no in-between), the metastable nature of the dynamic core can allow for a continuum of integration.
. In this model, metastable interactions in the thalamocortical region cause a process of selectionism through re-entry (a phenomenon describing the overall reciprocity and interactivity between signals in distant parts of the brain through coupled signal latency). Neuronal selectivity involves mechanochemical events that take place pre- and post-natally
whereby neuronal connections are influenced by environmental experiences. The modification of synaptic signals as it relates to the dynamic core provides further explanation for the DCH.
Despite growing evidence for the DCH, the ability to generate mathematical constructs to model and predict dynamic core behavior has been slow to progress. Continued development of stochastic processes designed to graph neuronal signals as chaotic and non-linear has provided some algorithmic basis for analyzing how chaotic environmental signals are coupled to enhance selectivity of neural outgrowth
or coordination in the dynamic core.
One interesting aspect of the GNW is that with sufficient intensity and length over which a signal travels, a small initiation signal can be compounded to activate an "ignition" of a critical spike-inducing state. This idea is analogous to a skier on the slope of a mountain, who, by disrupting a few blocks of ice with his skis, initiates a giant avalanche
in his wake. To help prove the circuit-like amplification theory, research has shown that inducing lesions in long-distance connections corrupts performance in integrative models.
A popular experiment to demonstrate the global workspace hypothesis involves showing a subject a series of backward-masked visual words
(e.g., "the dog sleeps quietly" is shown as "ylteiuq speels god eht") and then asking the subject to identify the forward "translation" of these words. Not only did fMRI detect activity in the word-recognition portion of the cortex, but additionally, activity is often detected in the parietal and prefrontal cortices
. In almost every experiment, conscious input in word and audition
tasks shows a much wider use of integrated portions of the brain than in identical unconscious input. The wide distribution and constant signal transfer between different areas of the brain in experimental results is a common method to attempt to prove the neural workspace hypothesis. More studies are being conducted to determine precisely the correlation between conscious and unconscious task deliberation in the realm of the global workspace.
, stroke
, and schizophrenia. Undoubtedly, spatiotemporal imaging techniques such as MEG and fMRI will elaborate on results already gleaned from analysis of EEG output.
An interest in the effect of a traumatic or semi-traumatic brain injury (TBI
) on the coordinated dynamical system has developed in the last five years as the number of TBI cases has risen from war-related injuries.
Computational neuroscience
Computational neuroscience is the study of brain function in terms of the information processing properties of the structures that make up the nervous system...
, the theory of metastability refers to the human brain’s
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
ability to integrate several functional parts and to produce neural oscillations
Neural oscillations
Neural oscillation is rhythmic or repetitive neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms localized within individual neurons or by interactions between neurons...
in a cooperative and coordinated manner, providing the basis for conscious
Consciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
activity.
Metastability, a state in which signals (such as oscillatory waves) fall outside their natural equilibrium state but persist for an extended period of time, is a principle that describes the brain’s ability to make sense out of seemingly random environmental cues. In the past 25 years, interest in metastability and the underlying framework of nonlinear dynamics has been fueled by advancements in the methods by which computers model brain activity.
Overview
EEGEEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
measures the gross electrical activity of the brain that can be observed on the surface of the skull. In the metastability theory, EEG outputs produce oscillations that can be described as having identifiable patterns that correlate with each other at certain frequencies. Each neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
in a neuronal network normally outputs a dynamical oscillatory waveform, but also has the ability to output a chaotic
Chaos theory
Chaos theory is a field of study in mathematics, with applications in several disciplines including physics, economics, biology, and philosophy. Chaos theory studies the behavior of dynamical systems that are highly sensitive to initial conditions, an effect which is popularly referred to as the...
waveform. When neurons are integrated into the neural network by interfacing neurons with each other, the dynamical oscillations created by each neuron can be combined to form highly predictable EEG oscillations.
By identifying these correlations and the individual neurons that contribute to predictable EEG oscillations, scientists can determine which cortical domains
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
are processing in parallel and which neuronal networks are intertwined. In many cases, metastability describes instances in which distal parts of the brain interact with each other to respond to environmental stimuli.
Frequency Domains of Metastability
It has been suggested that one integral facet of brain dynamics underlying conscious thought is the brain’s ability to convert seemingly noisyElectronic noise
Electronic noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly, as it can be produced by several different effects...
or chaotic signals into predictable oscillatory patterns.
In EEG oscillations of neural networks, neighboring waveform frequencies are correlated on a logarithmic scale
Logarithmic scale
A logarithmic scale is a scale of measurement using the logarithm of a physical quantity instead of the quantity itself.A simple example is a chart whose vertical axis increments are labeled 1, 10, 100, 1000, instead of 1, 2, 3, 4...
rather than a linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...
scale. As a result, mean frequencies in oscillatory bands cannot link together according to linearity of their mean frequencies. Instead, phase transitions are linked according to their ability to couple with adjacent phase shifts in a constant state of transition between unstable and stable phase synchronization
Synchronization
Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....
. This phase synchronization forms the basis of metastable behavior in neural networks.
Metastable behavior occurs at the high frequency
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
domain known as 1/f regime
Pink noise
Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power...
. This regime describes an environment in which a noisy signal (also known as pink noise
Pink noise
Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power...
) has been induced, where the amount of power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
the signal outputs over a certain bandwidth (its power spectral density) is inversely proportional to its frequency.
Noise at the 1/f regime can be found in many biological systems – for instance, in the output of a heartbeat in an ECG waveform—but serves a unique purpose for phase synchrony in neuronal networks. At the 1/f regime, the brain is in the critical state necessary for a conscious response to weak or chaotic environmental signals because it can shift the random signals into identifiable and predictable oscillatory waveforms. While often transient, these waveforms exist in a stable form long enough to contribute to what can be thought of as conscious response to environmental stimuli.
Oscillatory Activity and Coordination Dynamics
The dynamical system model, which represents networks composed of integrated neural systems communicating with one another between unstable and stable phases, has become an increasingly popular theory underpinning the understanding of metastability. Coordination dynamics forms the basis for this dynamical system model by describing mathematical formulae and paradigms governing the coupling of environmental stimuli to their effectors. History of Coordination Dynamics and the Haken-KelsoJ. A. Scott KelsoJ. A. Scott Kelso is a neuroscientist, and Professor of Complex Systems and Brain Sciences, Professor of Psychology, Biological Sciences and Biomedical Science at Florida Atlantic University in Boca Raton, Florida and The University of Ulster in Derry, N...
-Bunz (HKB) Model
The so-named HKB model is one of the earliest and well-respected theories to describe coordination dynamics in the brain. In this model, the formation of neural networks can be partly described as self-organizationSelf-organization
Self-organization is the process where a structure or pattern appears in a system without a central authority or external element imposing it through planning...
, where individual neurons and small neuronal systems aggregate and coordinate to either adapt or respond to local stimuli or to divide labor and specialize
Specialization (functional)
Specialization is the separation of tasks within a system. In a multicellular creature, cells are specialized for functions such as bone construction or oxygen transport. In capitalist societies, individual workers specialize for functions such as building construction or gasoline transport...
in function.
In the mid-1980s HKB model experiments, subjects were asked to wave one finger on each hand in two modes of direction: first, known as out of phase, both fingers moving in the same direction back and forth (as windshield wipers might move); and second, known as in-phase, where both fingers come together and move away to and from the midline of the body. To illustrate coordination dynamics, the subjects were asked to move their fingers out of phase with increasing speed until their fingers were moving as fast as possible. As movement approached its critical speed, the subjects’ fingers were found to move from out-of-phase (windshield-wiper-like) movement to in-phase (toward midline movement).
The HKB model, which has also been elucidated by several complex mathematical descriptors, is still a relatively simple but powerful way to describe seemingly-independent systems that come to reach synchrony just before a state of self-organized criticality
Self-organized criticality
In physics, self-organized criticality is a property of dynamical systems which have a critical point as an attractor. Their macroscopic behaviour thus displays the spatial and/or temporal scale-invariance characteristic of the critical point of a phase transition, but without the need to tune...
.
Evolution of Cognitive Coordination Dynamics
In the last 10 years, the HKB model has been reconciled with advanced mathematical models and supercomputer-based computation to link rudimentary coordination dynamics to higher-order processes such as learning and memory.The traditional EEG is still useful to investigate coordination between different parts of the brain. 40 Hz gamma wave
Gamma wave
A gamma wave is a pattern of neural oscillation in humans with a frequency between 25 to 100 Hz, though 40 Hz is prototypical.According to a popular theory, gamma waves may be implicated in creating the unity of conscious perception...
activity is a prominent example of the brain’s ability to be modeled dynamically and is a common example of coordination dynamics. Continuous study of these and other oscillations has led to an important conclusion: analyzing waves as having a common signal phase but a different amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
leads to the possibility that these different signals serve a synergistic function.
It is interesting to note some unusual characteristics of these waves: they are virtually simultaneous and have a very short onset latency, which implies that they operate faster than synaptic conduction
Chemical synapse
Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie...
would allow; and that their recognizable patterns are sometimes interrupted by periods of randomness
Randomness
Randomness has somewhat differing meanings as used in various fields. It also has common meanings which are connected to the notion of predictability of events....
. The latter idiosyncrasy has served as the basis for assuming an interaction and transition between neural subsystems. Analysis of activation and deactivation of regions of the cortex has shown a dynamic shift between dependence and interdependence
Interdependence
Interdependence is a relation between its members such that each is mutually dependent on the others. This concept differs from a simple dependence relation, which implies that one member of the relationship can function or survive apart from the other....
, reflecting the brain’s metastable nature as a function of a coordinated dynamical system.
fMRI, large-scale electrode arrays
Electrode array
An electrode array is a configuration of electrodes used for measuring either an electric current or voltage. Some electrode arrays can operate in a bidirectional fashion, in that they can also be used to provide a stimulating pattern of electric current or voltage.Common arrays...
, and MEG
Magnetoencephalography
Magnetoencephalography is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs...
expand upon the patterns seen in EEG by providing visual confirmation of coordinated dynamics. The fMRI, which provides an improvement over EEG in spatiotemporal characterization, allows researchers to stimulate certain parts of the brain with environmental cues and observe the response in a holistic brain model
Holism in science
Holism in science, or Holistic science, is an approach to research that emphasizes the study of complex systems. This practice is in contrast to a purely analytic tradition which aims to gain understanding of systems by dividing them into smaller composing elements and gaining understanding of the...
. Additionally, the fMRI has a response time of about one millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
, allowing for a virtually real-time investigation of the active turning –on and –off of selected parts of the brain in response to environmental cues and conscious tasks.
Social Coordination Dynamics and the Phi Complex
A developing field in coordination dynamics involves the theory of social coordination, which attempts to relate the DC to normal human development of complex social cues following certain patterns of interaction. This work is aimed at understanding how human social interaction is mediated by metastability of neural networks. fMRI and EEG are particularly useful in mapping thalamocortical response to social cues in experimental studies.A new theory called the Phi complex
Phi complex
The phi complex is a brain rhythm in the awake human brain that appears to serve various social functions. Phi is one of several brain rhythms in the awake human brain that coordinate human behavior. "Phi" operates in the 10-Hz band , and is located above the right centro-parietal cortex...
has been developed by J. A. Scott Kelso
J. A. Scott Kelso
J. A. Scott Kelso is a neuroscientist, and Professor of Complex Systems and Brain Sciences, Professor of Psychology, Biological Sciences and Biomedical Science at Florida Atlantic University in Boca Raton, Florida and The University of Ulster in Derry, N...
and fellow researchers at Florida Atlantic University
Florida Atlantic University
Florida Atlantic University, also referred to as FAU or Florida Atlantic, is a public, coeducational, research university located in , United States. The university has six satellite campuses located in the Florida cities of Dania Beach, Davie, Fort Lauderdale, Jupiter, Port St. Lucie, and in Fort...
to provide experimental results for the theory of social coordination dynamics. In Kelso's experiments, two subjects were separated by an opaque barrier and asked to wag their fingers; then the barrier was removed and the subjects were instructed to continue to wag their fingers as if no change had occurred. After a short period, the movements of the two subjects sometimes became coordinated and synchronized (but other times continued to be asynchronous). The link between EEG and conscious social interaction is described as Phi, one of several brain rhythms operating in the 10 Hz range. Phi consists of two components: one to favor solitary behavior and another to favor interactive (interpersonal) behavior. Further analysis of Phi may reveal the social and interpersonal implications of degenerative diseases such as schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
-- or may provide insight into common social relationships such as the dynamics of alpha and omega-males or the popular bystander effect
Bystander effect
The bystander effect or Genovese syndrome is a social psychological phenomenon that refers to cases where individuals do not offer any means of help in an emergency situation to the victim when other people are present...
describing how people diffuse personal responsibility in emergency situations depending on the number of other individuals present.
The Dynamic Core
A second theory of metastability involves a so-called dynamic core, which is a term to loosely describe the thalamocortical region believed to be the integration center of consciousness. The dynamic core hypothesis (DCH) reflects the use and disuse of interconnected neuronal networks during stimulation of this region. A computer model of 65,000 spiking neurons shows that neuronal groups existing in the cortex and thalamusThalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
interact in the form of synchronous oscillation. The interaction between distinct neuronal groups forms the dynamic core and may help explain the nature of conscious experience. A critical feature of the DCH is that instead of thinking binarily about transitions between neural integration and non-integration (i.e., that the two are either one or the other with no in-between), the metastable nature of the dynamic core can allow for a continuum of integration.
Neural Darwinism
One theory used to integrate the dynamic core with conscious thought involves a developing concept known as neural DarwinismNeural Darwinism
Neural Darwinism, a large scale theory of brain function by Gerald Edelman, was initially published in 1978, in a book called The Mindful Brain...
. In this model, metastable interactions in the thalamocortical region cause a process of selectionism through re-entry (a phenomenon describing the overall reciprocity and interactivity between signals in distant parts of the brain through coupled signal latency). Neuronal selectivity involves mechanochemical events that take place pre- and post-natally
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
whereby neuronal connections are influenced by environmental experiences. The modification of synaptic signals as it relates to the dynamic core provides further explanation for the DCH.
Despite growing evidence for the DCH, the ability to generate mathematical constructs to model and predict dynamic core behavior has been slow to progress. Continued development of stochastic processes designed to graph neuronal signals as chaotic and non-linear has provided some algorithmic basis for analyzing how chaotic environmental signals are coupled to enhance selectivity of neural outgrowth
Axon guidance
Axon guidance is a subfield of neural development concerning the process by which neurons send out axons to reach the correct targets...
or coordination in the dynamic core.
The Global Workspace Hypothesis
The global workspace hypothesis is another theory to elucidate metastability, and has existed in some form since 1983. This hypothesis focuses again on re-entry, the ability of a routine or process to be used by multiple parts of the brain simultaneously. Both the DC and global neuronal workspace (GNW) models involve re-entrance, but the GNW model elaborates on re-entrant connectivity between distant parts of the brain and long-range signal flow. Workspace neurons are similar anatomically but separated spatially from each other.One interesting aspect of the GNW is that with sufficient intensity and length over which a signal travels, a small initiation signal can be compounded to activate an "ignition" of a critical spike-inducing state. This idea is analogous to a skier on the slope of a mountain, who, by disrupting a few blocks of ice with his skis, initiates a giant avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...
in his wake. To help prove the circuit-like amplification theory, research has shown that inducing lesions in long-distance connections corrupts performance in integrative models.
A popular experiment to demonstrate the global workspace hypothesis involves showing a subject a series of backward-masked visual words
Backmasking
Backmasking is a recording technique in which a sound or message is recorded backward on to a track that is meant to be played forward...
(e.g., "the dog sleeps quietly" is shown as "ylteiuq speels god eht") and then asking the subject to identify the forward "translation" of these words. Not only did fMRI detect activity in the word-recognition portion of the cortex, but additionally, activity is often detected in the parietal and prefrontal cortices
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
. In almost every experiment, conscious input in word and audition
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
tasks shows a much wider use of integrated portions of the brain than in identical unconscious input. The wide distribution and constant signal transfer between different areas of the brain in experimental results is a common method to attempt to prove the neural workspace hypothesis. More studies are being conducted to determine precisely the correlation between conscious and unconscious task deliberation in the realm of the global workspace.
The Operational Architectonics Theory of Brain~Mind
Although the concept of metastability has been around in the Neuroscience for some time, the specific interpretation of metastability in the context of brain operations of different complexity has been developed by Andrew and Alexander Fingelkurts within their model of Operational Architectonics of brain~mind functioning. Metastability is basically a theory of how global integrative and local segregative tendencies coexist in the brain. The Operational Architectonics is centered around the fact that in the metastable regime of brain functioning, the individual parts of the brain exhibit tendencies to function autonomously at the same time as they exhibit tendencies for coordinated activity. In accordance with Operational Architectonics, the synchronized operations produced by distributed neuronal assemblies constitute the metastable spatial-temporal patterns. They are metastable because intrinsic differences in the activity between neuronal assemblies are sufficiently large that they do each their own job (operation), while still retaining a tendency to be coordinated together in order to realize the complex brain operation.The Future of Metastability
In addition to study investigating the effects of metastable interactions on traditional social function, much research will likely focus on determining the role of the coordinated dynamic system and the global workspace in the progression of debilitating diseases such as Alzheimer’s Disease, Parkinson's DiseaseParkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, and schizophrenia. Undoubtedly, spatiotemporal imaging techniques such as MEG and fMRI will elaborate on results already gleaned from analysis of EEG output.
An interest in the effect of a traumatic or semi-traumatic brain injury (TBI
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
) on the coordinated dynamical system has developed in the last five years as the number of TBI cases has risen from war-related injuries.
See also
- ConsciousnessConsciousnessConsciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
- Cognitive PsychologyCognitive psychologyCognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....
- Computational NeuroscienceComputational neuroscienceComputational neuroscience is the study of brain function in terms of the information processing properties of the structures that make up the nervous system...
- Electroencephalogram
- Functional MRI
- MagnetoencephalographyMagnetoencephalographyMagnetoencephalography is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs...
- Neural DarwinismNeural DarwinismNeural Darwinism, a large scale theory of brain function by Gerald Edelman, was initially published in 1978, in a book called The Mindful Brain...
- Self-organizationSelf-organizationSelf-organization is the process where a structure or pattern appears in a system without a central authority or external element imposing it through planning...
External links
- The Human Brain and Behavior Laboratory - Florida Atlantic University
- Laboratory for Coordination Dynamics - Florida Atlantic University
- BM-Science - Brain & Mind Technologies Research Centre, Finland
- An update on the global workspace theory - article discussing the global workspace theory in the context of metastability in the brain.