Meta-chemical Meta-chemical Control of Brain Control of Brain and Behaviourand Behaviour

V. Sutanovac

ContentsContents ChaptersChapters

I Sensitive periods in the I Sensitive periods in the development of brain and development of brain and behaviourbehaviour

II Perceptual control |II Perceptual control |theorytheory

III Perceptual control |III Perceptual control |practicepractice

ExamplesExamples

Ch. ICh. I

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Sensitive period –Sensitive period – point in point in one's existence wone's existence when effect hen effect of experience on the brain is of experience on the brain is particularly strong during a particularly strong during a

limited period in limited period in developmentdevelopment

Critical period point –Critical period point – in one's in one's existence whenexistence when experience experience

provides information provides information essential for normal essential for normal

development, altering development, altering performance permanentlyperformance permanently

Sensitive periods in the Sensitive periods in the development of Brain and development of Brain and BehaviourBehaviour

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Although reflected in behavior, Although reflected in behavior, actually property of neural circuitsactually property of neural circuits

HYPOTHESIS - experience during a HYPOTHESIS - experience during a sensitive period modifies sensitive period modifies architecture of a circuit in architecture of a circuit in

fundamental ways, causing certain fundamental ways, causing certain patterns of connectivity to become patterns of connectivity to become

highly stable and energetically highly stable and energetically preferredpreferred

Understanding at circuit level, as Understanding at circuit level, as well as relationship between well as relationship between

circuit properties and behavior, circuit properties and behavior, provides deeper insight into critical provides deeper insight into critical

role experience plays in shaping role experience plays in shaping development of brain and behaviordevelopment of brain and behavior

Sensitivity, what's it all Sensitivity, what's it all about?about?

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Learning that occurs during sensitive Learning that occurs during sensitive periods lays the foundation for periods lays the foundation for

future learning and exerts long-future learning and exerts long-lasting influence on development of lasting influence on development of

individual’s social and emotional individual’s social and emotional behavior behavior

Critical periods - special class of Critical periods - special class of sensitive periods that result in sensitive periods that result in

irreversible changes in brain functionirreversible changes in brain function

experience must be of a particular experience must be of a particular kind and it must occur within a kind and it must occur within a

certain period if the behavior is to certain period if the behavior is to developdevelop

Sensitivity and initial Sensitivity and initial learninglearning

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behavior results from behavior results from information that has been information that has been

processed through hierarchies processed through hierarchies of neural circuitsof neural circuits

to define sensitive periods and to define sensitive periods and to explore why they occur and to explore why they occur and

how they might be how they might be manipulated, must think about manipulated, must think about

them at the level of circuitsthem at the level of circuits

The circuitry of The circuitry of BehaviourBehaviour

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Not all circuits are shaped during Not all circuits are shaped during sensitive periodssensitive periods

Maintain high degree of plasticity Maintain high degree of plasticity throughout life, such as basolateral throughout life, such as basolateral nucleus of the amygdala, molecular nucleus of the amygdala, molecular

layer of the cerebellar cortex layer of the cerebellar cortex

When a circuit can select from large When a circuit can select from large range of potential patterns of range of potential patterns of

connectivity effect of experience connectivity effect of experience can have an enormous impact on its can have an enormous impact on its

connectivity connectivity

Conversely, when range of potential Conversely, when range of potential patterns of connectivity is highly patterns of connectivity is highly

constrained by genetic influences, constrained by genetic influences, effect of experience is effect of experience is correspondingly smallcorrespondingly small

Opening of sensitive Opening of sensitive periods initial conditions|periods initial conditions|

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1) information provided to circuit 1) information provided to circuit must be sufficiently reliable and must be sufficiently reliable and

precise to allow the circuit to carry precise to allow the circuit to carry out its function out its function

2) 2) circuit must contain adequate circuit must contain adequate connectivity (both excitatory and connectivity (both excitatory and

inhibitory connections) to process inhibitory connections) to process the informationthe information

3) activated mechanisms that enable 3) activated mechanisms that enable plasticity:plasticity:

a) capacity for altering axonal or a) capacity for altering axonal or dendritic morphologiesdendritic morphologies

b) making or eliminating synapses b) making or eliminating synapses c) changing strengths of synaptic c) changing strengths of synaptic

connections connections

Sensitive period Sensitive period prerequisitesprerequisites

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may be enabled bymay be enabled by1) progress of development 1) progress of development

2) individual’s experience2) individual’s experience

intense impulse activity (can intense impulse activity (can result from experience) shown result from experience) shown

to trigger:to trigger:1) gene transcription and 1) gene transcription and

translationtranslation2) activate existing molecular 2) activate existing molecular

cascades for processes cascades for processes underlying plasticity underlying plasticity

Sensitive periods timing |Sensitive periods timing |of initiationof initiation

Ch. ICh. I

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Experience →Experience →

1) customizes a developing neural 1) customizes a developing neural circuit to the needs of the individual circuit to the needs of the individual

2) provides precise information 2) provides precise information about the individual or about about the individual or about

environment that often cannot be environment that often cannot be predicted and, therefore, genetically predicted and, therefore, genetically

encodedencoded

3) calibrates the circuits that process 3) calibrates the circuits that process stereoscopic information and stereoscopic information and

customizes circuits involved in customizes circuits involved in processing speech sounds for the processing speech sounds for the particular language(s) that will be particular language(s) that will be

spokenspokenDuring a sensitive period |During a sensitive period |experience and sens-experience and sens-period plasticityperiod plasticity

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predisposition of a circuit to predisposition of a circuit to be instructed by typical be instructed by typical

experience reflects:experience reflects:

1) selectivity of the circuit’s 1) selectivity of the circuit’s various inputs (may be various inputs (may be shaped during sensitive shaped during sensitive

periods)periods)2) innate connectivity of the 2) innate connectivity of the

circuit.circuit. Reflections Reflections of the circuitof the circuit

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1) axon elaboration and synapse 1) axon elaboration and synapse formation formation

2) axon and synapse elimination 2) axon and synapse elimination (shown to alter circuit (shown to alter circuit

architecture during sensitive architecture during sensitive periods) periods)

3) synapse consolidation 3) synapse consolidation

* Hebbian rule - activity of a * Hebbian rule - activity of a tentative, presynaptic element tentative, presynaptic element

consistently anticipates (contributes consistently anticipates (contributes to driving) the activity of a to driving) the activity of a

postsynaptic neuron, that synapse is postsynaptic neuron, that synapse is stabilized and strengthenedstabilized and strengthened

distribution of stabilized distribution of stabilized synapses shapes growth patterns synapses shapes growth patterns

of axons and dendrites of axons and dendrites

Mechanisms of sensitive Mechanisms of sensitive period plasticityperiod plasticity

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Mechanisms of sensitive Mechanisms of sensitive period plasticityperiod plasticity

Ch. ICh. I

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*Hypothesis - experience during a *Hypothesis - experience during a sensitive period potentiates sensitive period potentiates specific synapses which are specific synapses which are structurally stabilized by the structurally stabilized by the

insertion of particular kinds of insertion of particular kinds of CAMs CAMs

synapses become invulnerable to synapses become invulnerable to elimination, even if functional elimination, even if functional efficacy was to drop to zero efficacy was to drop to zero

persistence suggests they become persistence suggests they become relatively invulnerable to relatively invulnerable to

elimination, because they have elimination, because they have been consolidated by a particular been consolidated by a particular

kind of CAM kind of CAM

Mechanisms of Mechanisms of architectural change architectural change underlying Sensitive underlying Sensitive periodsperiods

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has a unique advantage in has a unique advantage in shaping the connectivity of a shaping the connectivity of a

circuitcircuit

Intense and repeated activation Intense and repeated activation alters the circuit conditions alters the circuit conditions

dramaticallydramatically

Although may have a uniquely Although may have a uniquely potent effect in shaping patterns potent effect in shaping patterns

of connectivity, subsequent of connectivity, subsequent experience has the ability to experience has the ability to cause further structural and cause further structural and

functional changes as long as the functional changes as long as the sensitive period remainssensitive period remains

openopenUnique advantage of Unique advantage of initial experienceinitial experience

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Unique advantage of Unique advantage of initial experienceinitial experience

The pattern of connectivity The pattern of connectivity instructed by experience instructed by experience

becomes more sharply defined becomes more sharply defined and highly preferred, even and highly preferred, even though the pattern may be though the pattern may be

atypicalatypical

Ch. ICh. I

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instructs a new pattern of connectivity, instructs a new pattern of connectivity, extra energy must be expended to extra energy must be expended to

overcome the influences that stabilize the overcome the influences that stabilize the initial patterninitial pattern

Repeated experience that instructs new Repeated experience that instructs new pattern of connectivity refines and pattern of connectivity refines and

stabilizes the new pattern, creating a new stabilizes the new pattern, creating a new low point in the landscapelow point in the landscape

humans are able to learn multiple languages humans are able to learn multiple languages with equal facility during a sensitive period with equal facility during a sensitive period

(Doupe & Kuhl, 1999)(Doupe & Kuhl, 1999)

Ch. ICh. I

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‘‘‘‘stability landscape’’- stability landscape’’- functional implications of the functional implications of the cellular and molecular events cellular and molecular events for the future performance of for the future performance of

a circuita circuit

represents the range of represents the range of possible connectivity patterns possible connectivity patterns

circuit might acquire and circuit might acquire and degree to which any degree to which any

particular pattern is preferredparticular pattern is preferred

““Stability landscape” as a Stability landscape” as a metaphor for sensitive metaphor for sensitive period plasticity period plasticity

Ch. ICh. I

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Ending of Ending of sensitive periodssensitive periods

change may still occur (as long change may still occur (as long as not a critical period) but extra as not a critical period) but extra energy required for a circuit to energy required for a circuit to

maintain a less stable pattern of maintain a less stable pattern of connectivityconnectivity

critical period ends - alternative critical period ends - alternative patterns of connectivity are no patterns of connectivity are no

longer possible due to the longer possible due to the properties of the circuit’s properties of the circuit’s

stability landscapestability landscape

Ch. ICh. I

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- (as a function of developmental - (as a function of developmental stage) involve circuits that have stage) involve circuits that have the potential to learn multiple, the potential to learn multiple, stable patterns of connectivity stable patterns of connectivity

during the sensitive period during the sensitive period

that end rapidly involve circuits that end rapidly involve circuits with strong innate with strong innate

predispositions to be shaped by predispositions to be shaped by certain kinds of stimulicertain kinds of stimuli

These circuits learn to respond to These circuits learn to respond to a particular stimulus - once the a particular stimulus - once the circuit acquires selectivity for circuit acquires selectivity for

that stimulus, subsequent that stimulus, subsequent experience has little or no effectexperience has little or no effect

Ending of Ending of sensitive periodssensitive periods

Ch. ICh. I

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irreversible changes in neural circuit irreversible changes in neural circuit do not necessarily mean irreversible do not necessarily mean irreversible

changes in complex behaviorchanges in complex behavior

To minimize contradictions in the To minimize contradictions in the interpretation ofinterpretation of

behavioral observations, essential to behavioral observations, essential to analyze behavior into elementary analyze behavior into elementary components that reflect specific components that reflect specific

levels of neural processing shaped by levels of neural processing shaped by experienceexperience

critical periods act at the level of critical periods act at the level of specific neural circuits, to avoid specific neural circuits, to avoid

apparent contradictions essential to apparent contradictions essential to analyze a critical period in the circuit analyze a critical period in the circuit

in which it occurs.in which it occurs.Critical periods for Critical periods for circuits vs. behaviourcircuits vs. behaviour

Ch. ICh. I

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During sensitive period, During sensitive period, particular kinds of experience particular kinds of experience

shape the connectivity of a shape the connectivity of a circuit in fundamental ways, circuit in fundamental ways, causing certain patterns of causing certain patterns of

connectivity to become connectivity to become energetically preferred or energetically preferred or mechanistically specifiedmechanistically specified

Critical periods - a subset of Critical periods - a subset of sensitive periods for which the sensitive periods for which the

instructive influence of instructive influence of experience is essential for experience is essential for typical circuit performance typical circuit performance (effects of experience on (effects of experience on

performance are irreversible)performance are irreversible)

In RetrospectIn Retrospect

Ch. IICh. II

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● William T. (Bill) Powers began William T. (Bill) Powers began in early 1950s by applying in early 1950s by applying control engineering and control engineering and

natural science to the subject natural science to the subject of psychologyof psychology

● Control theory explains how Control theory explains how organisms can control what organisms can control what

happens to themhappens to them

● explains what a goal is, how explains what a goal is, how goals relate to behavior, how goals relate to behavior, how

behavior affects perceptions, behavior affects perceptions, how perceptions define reality how perceptions define reality we live in and move and have we live in and move and have

our beingour beingPerceptual control|Perceptual control|in theoryin theory

Ch. IICh. II

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● behavior IS orderly behavior IS orderly

● CONSEQUENCES of output forces CONSEQUENCES of output forces are shaped by organism into are shaped by organism into

highly regular and reliably highly regular and reliably repeatable states and patternsrepeatable states and patterns

● IMPORTANT: how much you know IMPORTANT: how much you know about the outcomes that are under about the outcomes that are under

controlcontrol

● confusion is all in the eye of the confusion is all in the eye of the beholder beholder

● Each person controls one Each person controls one contribution to the pattern that all contribution to the pattern that all

perceive, in such a way as to perceive, in such a way as to preserve the higher-level pattern preserve the higher-level pattern as each person desires to see itas each person desires to see it

On the obviousOn the obvious

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● once we understood the once we understood the orderliness of simple acts and their orderliness of simple acts and their

immediate consequences, we immediate consequences, we should be able to go on and should be able to go on and

understand more general patterns understand more general patterns

● We must explore all levels - what We must explore all levels - what we find at each level makes sense we find at each level makes sense only in the context of the othersonly in the context of the others

● PCT: PCT: ● focuses on how we look at and focuses on how we look at and

experience things, and the way experience things, and the way these perceptions are compared these perceptions are compared

with experiences we wantwith experiences we want● explains how thoughts become explains how thoughts become

actions and feelings and why actions and feelings and why stimuli appear to cause responsesstimuli appear to cause responses

On the obviousOn the obvious

Ch. IICh. II

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● ProposesProposes - nervous system is - nervous system is made up of large number of made up of large number of

control systems in a control systems in a hierarchical arrangement, each hierarchical arrangement, each

a simple circuit of neurons a simple circuit of neurons which quickly and efficiently which quickly and efficiently can perform the way we docan perform the way we do

● OffersOffers - explanation - explanation of how of how purposeful behavior works and purposeful behavior works and

what it accomplisheswhat it accomplishes

● ExplainsExplains - behavior from inside - behavior from inside perspective of controlling perspective of controlling organism rather than from organism rather than from

outside perspective of outside perspective of observerobserver

People as living things: People as living things: The storyThe story

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● Control of input by means of Control of input by means of output - defining characteristic output - defining characteristic distinguishing living things from distinguishing living things from

inanimate objectsinanimate objects

● Essence (of PCT method) - to Essence (of PCT method) - to apply a force, stimulus or apply a force, stimulus or

disturbance to an object and disturbance to an object and observe the result or reactionobserve the result or reaction

● If a force/stimulus is applied to If a force/stimulus is applied to a variable that a living organism a variable that a living organism perceives and is controlling, the perceives and is controlling, the

organism produces organism produces countervailing forces to countervailing forces to

maintain that variable in states maintain that variable in states that it prefersthat it prefers

People as living things: People as living things: The storyThe story

Ch. IICh. II

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* a theory of human * a theory of human communication is an extension communication is an extension of our efforts to explain brain of our efforts to explain brain

and behaviorand behavior

our beliefs about the brain our beliefs about the brain should have direct implications should have direct implications

for our characterization of for our characterization of language (vice versa)language (vice versa)

Hierarchical Perceptual Control Hierarchical Perceptual Control Theory (HPCT) one of –Theory (HPCT) one of –

theories addressing the brain-theories addressing the brain-language connection islanguage connection isLanguage: control ofLanguage: control of

perceptionperception

Ch. IICh. II

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Powers’ insight was to Powers’ insight was to emphasize the role of behavior in emphasize the role of behavior in

perceptual controlperceptual control

language is just as purposeful as language is just as purposeful as other behaviorsother behaviors

- Language forms the basis for - Language forms the basis for most of our complex most of our complex

interactions..allows for possibility interactions..allows for possibility of resolving disputes and of resolving disputes and

conflicts without resorting to conflicts without resorting to violenceviolence

““higher” level variability in higher” level variability in

morphology and syntax may be morphology and syntax may be crucial, even life-threatening crucial, even life-threatening

(What did you call me?!)(What did you call me?!)Language: control ofLanguage: control ofperceptionperception

Ch. IICh. II

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HPCT offers a recast of HPCT offers a recast of important questions about important questions about

individual linguistic behaviourindividual linguistic behaviour

- If there is a hierarchy to If there is a hierarchy to perception in general, then the perception in general, then the same principles may apply to same principles may apply to

language as welllanguage as well

- If behavior is the control of - If behavior is the control of perception, then linguistic perception, then linguistic

behavior may be viewed as behavior may be viewed as control of perception as wellcontrol of perception as well

Language: control ofLanguage: control ofperceptionperception

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Any discussion of development Any discussion of development also raises the question of also raises the question of

critical periods: is there one or critical periods: is there one or more such periods for human more such periods for human

language?language?

A true critical period for A true critical period for “language” would involve “language” would involve virtually the entire brain! virtually the entire brain!

Alternative - multiple critical or Alternative - multiple critical or sensitive periods for: sensitive periods for:

1) configuration-related 1) configuration-related perceptual developmentperceptual development

2) transition-related perceptual 2) transition-related perceptual development etc.development etc.Perceptual control|Perceptual control|

in theoryin theory

Ch. IICh. II

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Linguistic behaviors result from Linguistic behaviors result from the interplay of various contextual the interplay of various contextual

and neurological factors and neurological factors (in PCT terms, reference levels and (in PCT terms, reference levels and

disturbances to them)disturbances to them)

The semantics for objects or for The semantics for objects or for concepts we use changes as we concepts we use changes as we

gain relevant experiencesgain relevant experiences

our [implicit] understanding of our [implicit] understanding of language grows and changes language grows and changes

through our experiencesthrough our experiences

These experiences form the basis These experiences form the basis for our decisions regarding such for our decisions regarding such

things as word choice (categories) things as word choice (categories) or lexical ordering (sequence).or lexical ordering (sequence).

Language and subjective Language and subjective perceptionsperceptions

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- move beyond “word-- move beyond “word-manipulation” to completely manipulation” to completely

understand connection between understand connection between language and behaviorlanguage and behavior

primary interest in effect we primary interest in effect we desire to produce upon the desire to produce upon the

listener and so are usually not listener and so are usually not attentive to the processes by attentive to the processes by which we produce the effect” which we produce the effect”

((Pillsbury and Meader; Bakhtin and Pillsbury and Meader; Bakhtin and Vygotsky)Vygotsky)

..“purpose,” “volition,” “will,” ..“purpose,” “volition,” “will,” “motive,” ..whatever this guiding “motive,” ..whatever this guiding

force may be, is ultimate force may be, is ultimate dictator of the whole process of dictator of the whole process of

speech (Dunkel 1948)speech (Dunkel 1948)

Language and subjective Language and subjective perceptionsperceptions

Ch. IIICh. III

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● neural processing in low-level neural processing in low-level cortices can be modulated by cortices can be modulated by

interactions between senses at interactions between senses at specific, early poststimulus time specific, early poststimulus time

periodsperiods

● early onset of cortical responses in early onset of cortical responses in humans to auditory relative to humans to auditory relative to

visual stimulation makes it visual stimulation makes it conceivable that auditory processes conceivable that auditory processes

can impact feedforward visual can impact feedforward visual processes within nominally visual processes within nominally visual cortices (Schroeder et al., 2004).cortices (Schroeder et al., 2004).

● evidence of auditory-driven evidence of auditory-driven responses within inferior parietal responses within inferior parietal

cortex of humans (Schroeder et al., cortex of humans (Schroeder et al., 2004) that represent a potential 2004) that represent a potential

basis for modulation of early basis for modulation of early sensory processing within visual sensory processing within visual

cortexcortex

Perceptual control|Perceptual control|in practicein practice

Ch. IIICh. III

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● auditory inputs particularly auditory inputs particularly well poised to impact visual well poised to impact visual processing not only at the processing not only at the lowest cortical levels but lowest cortical levels but

potentially at poststimulus potentially at poststimulus latencies (as short as 20 ms)latencies (as short as 20 ms)

● E.g. occipital TMS has E.g. occipital TMS has opposing effects on visual opposing effects on visual

and auditory stimulus and auditory stimulus detection over identical time detection over identical time

periodsperiods

● external auditory stimuli external auditory stimuli enhance visual cortex enhance visual cortex

excitability as measured by excitability as measured by induction via TMSinduction via TMS

Perceptual control|Perceptual control|in practicein practice

Ch. IIICh. III

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● overall pattern of results overall pattern of results indicates that there is a indicates that there is a

period during which period during which behavioral consequences of behavioral consequences of occipital TMS depend on the occipital TMS depend on the

sensory modality of external sensory modality of external inputsinputs

● results support the existence of results support the existence of early critical period for producing early critical period for producing

facilitative multisensory facilitative multisensory interactions and suggest interactions and suggest

auditory and visual inputs are auditory and visual inputs are converging within the occipital converging within the occipital

cortexcortexPerceptual control|Perceptual control|in practicein practice

Ch. IIICh. III

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● studies revealing visual studies revealing visual suppression by occipital TMS suppression by occipital TMS

(Amassian et al., 1989)(Amassian et al., 1989)

● showed that stimulation of a showed that stimulation of a given area can induce opposing given area can induce opposing

(disruptive or facilitative) (disruptive or facilitative) effects depending on task or effects depending on task or

behavioral context (Walsh et al., behavioral context (Walsh et al., 1998; Grosbras and Paus, 2002, 1998; Grosbras and Paus, 2002,

2003)2003)

● results imply that visual results imply that visual perception and brain plasticity perception and brain plasticity can be heavily influenced by a can be heavily influenced by a 'targeted' auditory stimulus, 'targeted' auditory stimulus,

(especially under occipital TMS)(especially under occipital TMS)Perceptual control|Perceptual control|in practicein practice

Thank'YThank'YVery MuchlyVery Muchly