Executive Skills Part 1: Definition, over-view, brain basis

Isabelle Rapin

Seminar in Developmental Disabilities

March 21, 2013No conflict of interest

NIH Tool Box Definition*Neurology March 12, 2013: S54-64

Executive function (cognitive control) = top-down cognitive modulation of goal directed activity• Set shifting

Lateral prefrontal, anterior cingular, inferior parietal network

• Attention and inhibitory control (visual)Frontal eye fields, posterior parietal, anterior cingulate, thalamus, basal ganglia network

• Working memoryPrefrontal, posterior parietal network

* Tests for uniform research projects

Definition Top-down executive/control system(s) --

enable(s) endogeneously-generated goal-directed behaviors

Some on-line requirements:• Planning (awareness of the future)• Motivation• Cognitive/behavioral flexibility (shifting)• Selective/focused attention• Inhibition of automatic sensory/affective responses• Sustaining active working memory• Exploit long-term memories (learning)

1. Schema of STM systems

Short Term Memory

Sensory buffers Working memory

Sensory cortices Prefrontal cortex

LTM declarative systems

Long term memory

Declarative(explicit,items))

Non-declarative(implicit skills, etc)

Episodic (individual)

Several subtypesSemantic

(knowledge)

More requirements

Awareness of problem to be solved Advance planning Self-awareness, -monitoring Meta-cognition/multi-tasking Self-control, delay gratification Attend to feedback, shift accordingly

Executive function: slowly maturing

Requires repeated experiences to develop Modular aspects

• Visuo-motor

• Sensori-motor

• Verbal

• Implicit/social

Considered “mature” @ start of 3rd decade Actually continues to develop life-long Susceptible to decay: dementia, frontal damage

Brodmann map in color

Brodmann (1909)

52 histologically distinct cortical areas

Prefrontal cortex

Gross anatomo-functional

approximations (most

functions are not localized)

Dorso-lateral prefrontal

~ area 48 working memory

Orbito-frontal

~ areas 10, 11, 47 inhibitory

Mesial prefrontal

~ areas 8-11, 13, 32 limbic

Scott, Schoenberg

Developmental disorders with prominently affected executive

skills

ADHD (attention deficit hyperactivity disorders)

ASD (autism spectrum disorders) Conduct disorders Etc.

Attention - Definition

Presupposes vigilance (RAS) Ability to make choices among a myriad of

competing stimuli in order to match task demands by• Enhancement of attended stimuli

• Suppression of unattended stimuli

Requires executive skills (prioritize, etc.) “ working memory

Overlaps with attention

Control of attention

Exogenous (reflexive, bottom-up – does not require conscious awareness)

Endogenous (cortical, top-down choices to match on-going needs)• Monitor & maintain goal directed activities

• Deactivate inappropriate tasks

• Prepare activation of relevant tasks

• Modulation by on-going affective signals

Major anatomic circuitry

Subcortical areas (multiple neurotransmitters)

• Midbrain (ascending RAS, raphé, etc.)

• Intralaminar nuclei of thalamus

• Diencephalon, caudate

Cortical areas (right dominant > left)• Inferior parietal – multimodal sensory processing

• Lateral prefrontal - working memory, executive

• Anterior cingulate - interface cognition & emotion

ADHD

↓ sustained attention → distractible ↓ working memory → forgetful ↓ response inhibition → impulsive ↓ input inhibition and response monitoring ↓ awareness of affective signals &

environmental rewards

Autism

Rigidity, narrow focus, perseveration Impaired awareness of social/

environmental cues But

• Selective/focused attention may be OK

• Inhibition of irrelevant sensory inputs may be OK

• Memory (working and long-term) may be OK

Overlaps with memory

Multiple Memory Systems

Short term memory systems• Sensory buffers (for each modality +

endogenous inputs from memory)

• Working memory

Long term memory systems• Declarative (or explicit)

• Non-declarative (or implicit)

Retrieval systems

1. Schema of STM systems

Short Term Memory

Sensory buffers Working memory

Sensory cortices Prefrontal cortex

Working Memory Circuitry

Prefrontal cortex: in continuous on-line reciprocal connections with• Sensory cortices for each modality (specific buffers)• Limbic circuits• Arousal circuits• Motor output circuits

* * * Note: Hippocampus circuitry: (data from amnestic

patients) • Not critical on-line, • Critical for long term storage

LTM declarative systems

Long term memory

Declarative(explicit,items))

Non-declarative(implicit skills, etc)

Episodic (individual)

Several subtypesSemantic

(knowledge)

Declarative (explicit) LTM1. Episodic (Tulving)

Uniquely human Powerful tool Specific particular facts/events

(autobiographical) Late to develop evolutionarily (man only?)

and ontogenitically (infant amnesia) Fragile to degeneration Critically dependent on (not limited to!)

hippocampal/medial temporal cortices

Declarative LTM Memory 2. Semantic Memory

Knowledge (as opposed to remembrance of specific facts)

“Picked-up” knowledge Starts at birth, long before episodic

memory Broad and powerful Much more resilient than episodic memory

Hippocampus system

Binds inputs from all sensory modalities with limbic and prefrontal executive inputs

Reciprocally connected with relevant cortical and subcortical circuitry

Required for declarative LT memory• For fresh and midterm declarative memories

• Not for very long term “ “

Not required for non-declarative memories

Executive Skills Part 2

Puja Patel

Seminar in Developmental Disabilities

March 20, 2013No conflict of interest