The Prefrontal Cortex – An Update: Time Is of the - PowerPoint Presentation

Slide1

The Prefrontal Cortex – An Update: Time Is of the Essence (Joaquin M. Fuster, 2001)

Action-Perception-Learning Cycles

2012-09-13

Chun,

Hyo

-sunSlide2

The Prefrontal Cortex – An Update: Time Is of the EssenceJoaquin M. Fuster, 2001The cognit

: A network model of cortical representation

Joaquin M.

Fuster

, 2006Slide3

Joaquin M. FusterProfessor of Psychiatry and Biobehavioral Sciences, UCLA

cortical mechanisms of cognitive functions

memory and the prefrontal

cortex

http

://www.joaquinfuster.com/Slide4

OverviewAnatomy and ConnectionsNeuropsychology of the PFCThe PFC in the Cortical Cognitive MapThe PFC in the Cortical Dynamics of Cognition

Memory and Set, for the Two Sides of Time

Cortical Mechanisms of Temporal Integration

ConclusionsSlide5

Anatomy and ConnectionsCerebral cortexPrefrontal cortexThree major regions of PFCDevelopment of PFC

ConnectionsSlide6

Cerebral cortexCerebral cortex is the out layer of the cerebrumIt plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness

It is organized in hierarchical manner

sensory and motor areas

s

pecific sensory and motor functions

PFC: representation and

execution of actionsSlide7

The prefrontal cortex (PFC)The PFC is the association cortex of the frontal lobe.The PFC constitutes the highest level of the cortical hierarchy dedicated to the representation and execution of actions

Frontal lobeSlide8

Three major regions of PFCorbital / medial / lateral

orbital and medial:

e

motional behavior

lateral:

t

emporal organization of behavior, speech, and reasoning

Two common errors:

1) to argue for one particular prefrontal function while opposing or neglecting others that complement it

2) to localize any of them within a discrete portion of PFCSlide9

Development of PFCPhylogenetically, PFC is one of the latest cortices to develop, having attained maximum relative growth in the human brain (

Brodmann

, 1912;

Jerison

, 1994)

The PFC undergoes late development in the course of ontogeny. (

Flechsig

, 1920;

Conel

, 1939;

Huttenlocher

, 1990;

Huttenlocher

and

Dabholkar

, 1997)Neuroimaging studies indicate that, in the human, prefrontal areas do not attain full maturity until adolescence. (Chugani

et al., 1987; Paus et al., 1999; Sowell et al., 1999)Thus, these areas are critical for higher cognitive functionsSlide10

ConnectionsThe functions of the PFC rely closely on its connections with a vast array of other cerebral structures.Brainstem, thalamus, basal ganglia, limbic systemThe

profuse variety of connections of the PFC is obviously related to the variety of the information it integrates

.

Those connections presumably constitute the structural frame of cognitive networks(

Fuster

, 1995)A cognit is one such

network(Ref)Slide11

Summary:Anatomy and ConnectionsCerebral cortex is organized in hierarchical manner

The

PFC is the association cortex of the frontal lobe

.

Three major regions of PFC: orbital / medial / lateral

Orbital and medial region: emotional behaviorLateral region: temporal integrationPhylogenetically

and ontogenetically, PFC

is one of the latest

part to develop.

These areas are critical for higher cognitive

functions

The complex connections with other cerebral structures are related to its function of integrationSlide12

Neuropsychology of the PFCLesions of orbital PFCLesions of medial PFCLesions of lateral PFCSlide13

Lesions of orbital PFCPhineas Gage Showed dramatic changes of personality

(

Damasio

et al., 1994;

Fuster

, 1997)Impulsive, disinhibited in a host of instinctual behaviors, irritable, contentious, and exhibit a severe disorder

of attention.

Thus, major role of

orbital PFC is to control

emotional behaviorSlide14

Lesions of medial PFCLoss of spontaneity and difficulty in the initiation of movements and speech (Verfaellie and Heilman

, 1987; Cummings, 1993)

Apathetic, disinterested in the environment, and unable to concentrate their attention on behavioral or cognitive tasks.

Neuroimaging of normal subjects shows marked activations of the medial region in tasks that demand sustained effort and concentrated attention (Posner et al., 1988;

Raichle

, 1994)

Thus, the major role of

medial PFC is to maintain attentionSlide15

Lesions of lateral PFCThe inability to formulate and to carry out plans and sequences of actions.The difficulty to consciously represent sequences of speech or behavior, especially if they are novel or complexThe difficulty to initiate sequences and to execute them in orderly manner

Thus, lateral PFC plays a crucial role in the organization and execution of behavior, speech, and reasoningSlide16

Summary:Neuropsychology of the PFCorbital PFC controls emotional

behavior

medial

PFC

helps to sustain attention

lateral PFC plays a crucial role in the organization and execution of behavior, speech, and reasoningSlide17

The PFC in the Cortical Cognitive MapThe cortex of the human appears divided by the Rolandic fissure into two major parts

The cortex of the occipital, temporal, and parietal lobes

Sensory functions - Perceptual memory

The cortex of the frontal lobe

Motor functions - Executive memorySlide18
Slide19

Summary:The PFC in the Cortical Cognitive MapPerceptual memory network

Executive memory network

These are organized hierarchically.Slide20

The PFC in the Cortical Dynamics of CognitionEncoding and retrieving memoryTemporal integrationSlide21

Encoding and retrieving memoryBy functional imaging methodsEncoding new memory activates the left more than the right PFC

Conversely, retrieving stored memory activates the right more than the left PFC

It is not clear that the asymmetric activations are attributable to their differential involvement in two cognitive operations

.Slide22

Temporal integration

Basal ganglia

Cerebellum

Lateral thalamus

PFCSlide23

Summary:The PFC in the Cortical Dynamics of CognitionIn fMRI studies, encoding new memory: left >> right PFC

retrieving stored memory: left <<

right

PFC

but, not clear dissociation of the function.

Routine sequences do not engage PFCNovel and complex sequences do engage PFCSlide24

Memory and Set, for the Two Sides of TimeWorking memory: “memory for action”Preparatory set: “memory of the future”Slide25

Temporal integrationExperiment(1) Brief tone from overhead loudspeaker(2) 10s delay

(3) two colors simultaneously in two buttons

(4) animal rewarded for choosing the color that matches the toneSlide26

ResultsFiring frequency histograms of two cellsTwo separated stimulus are integratedSlide27

Cortical Mechanisms of Temporal IntegrationThe mechanisms of temporal integration and the role of the PFC in them are still poorly understood.How are the components of an executive cortical network timely and selectively activated in the execution of a goal-directed sequence of behavior?

How is a cortical network maintained active in the process of bridging temporally separated components of the sequence?Slide28
Slide29
Slide30

Perception-action cycleThe behavior of an organism is subject to a continuous circular flow of information between itself and its environmentSlide31

ConclusionPFC: memory, planning, execution of actionsOrbital, medial: emotional behaviorLateral: temporal organization of behaviorPerceptual memory and Executive memory

Organized hierarchically

Temporal integration

Working memory, preparatory set

Perception-action cycleSlide32

Q1

Explain the general organization of cognitive representations of the human cortex in Figure

3. Is

it hierarchically organized?

What are the three major regions of the prefrontal cortex (PFC) and what are their functions?Slide33

Q1- answerTwo memory networkAnterior part(PFC) represents executive memoryPosterior part represents perceptual memory

Hierarchical,

heterarchical

Interacts

with each

otherOrbital / medial / lateral regionFunctionsOrbital, Medial: emotional behavior

Lateral: temporal organization of behaviorSlide34

Q2How are the actions temporally sequenced or integrated? Explain Figure 4. How does the cortex process a novel and complex sequence

?Slide35

Q2- answerRoutine, automatic, or overlearned behavioral sequences, however complex, do not engage the PFC and may be entirely organized in subcortical structures (basal ganglia, cerebellum, lateral thalamus, etc.)

Sequences with cross-temporal contingencies, or with ambiguities and uncertainties in their controlling stimuli or in their motor acts, do engage the PFC.Slide36

Q3

Explain

Figure 7. What is the experimental paradigm? What is the objective of the experiment? What is the conclusion of the experimental results? How sound and color are cross-temporally integrated in frontal cortex? Slide37

Q3- answerWhat is the experimental paradigm? What is the objective of the experiment?

To see the temporal integration in the PFC

What

is the conclusion of the experimental results?

Different kinds of temporally separated stimulus integrated at lateral PFC

How sound and color are cross-temporally integrated in frontal cortex

?Slide38

Q4Explain the cortical dynamics in the perception-action cycle in Figure 10.Slide39

Q4- answerThe behavior of an organism is subject to a continuous circular flow of information between itself and its environmentEnvironmental stimuli are received and processed by sensory structures;

as

a result of sensory processing,

actions are generated

that cause certain changes in the environment,

which lead to new sensory input, and so on.Working memory and preparatory set work together toward their goals in every sphere of action, including speech.Slide40

Q5-1Q5-1: Compare the modular models and network models of the cortex. How do they view the cortex differently? What can they explain and what they cannot?

Modular model

A discrete area of the cortex has functions

Most of these models have failed for lack of conclusive evidence

Network Model

Cognitive representations consist of widely distributed networks of cortical neurons

Only large cortical lesions were observed to lead to deficits in cognitive memory and function.Slide41

Q5-2What are the cognits? Explain the global architecture of the brain in terms of the cognits.

The network model postulates the memory and knowledge are represented by distributed, interactive, and overlapping networks of neurons in association cortex. Such networks are

cognits

.

They constitute the basic units of memory or knowledge. The association cortex of post-

rolandic region contains perceptual

cognit

, frontal-association cortex contains executive

cognit

. Slide42

Q5-3Explain the main cognitive functions of the brain in the following regions: posterior and frontal cortex, parasensory and premotor and prefrontal cortex?

-> Question 1Slide43

Q5-4 What brain connections are responsible for the perception-action cycle in sequential behavior, speech, and reasoning?Connections between posterior and frontal cortexSlide44

Q5-5What is a relation code? Why is it important? How is it different from other coding mechanisms known to be used in the brain?

the code of cortical representation is a relational code

Memories consist of networks made of connections between more or less widely dispersed neurons of the cortex of association