Understanding Executive Skills in Developmental Disorders

1. Executive SkillsPart 1: Definition, over-view, brain basis Isabelle Rapin Seminar in Developmental Disabilities March 21, 2013 No conflict of interest

2. NIH Tool Box Definition*NeurologyMarch 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 memory Prefrontal, posterior parietal network * Tests for uniform research projects

3. 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)

4. 1. Schema of STM systems Short Term Memory Sensory buffers Working memory Sensory cortices Prefrontal cortex

5. LTM declarative systems Long term memory Declarative (explicit,items)) Non-declarative (implicit skills, etc) Episodic (individual) Semantic (knowledge) Several subtypes

6. 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

7. 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

8. Brodmann map in color Brodmann (1909) 52 histologically distinct cortical areas

9. 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

10. Developmental disorders with prominently affected executive skills • ADHD (attention deficit hyperactivity disorders) • ASD (autism spectrum disorders) • Conduct disorders • Etc.

11. 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

12. Overlaps with attention

13. 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

14. 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

15. ADHD • ↓ sustained attention → distractible • ↓ working memory → forgetful • ↓ response inhibition → impulsive • ↓ input inhibition and response monitoring • ↓ awareness of affective signals & environmental rewards

16. 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

17. Overlaps with memory

18. 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

19. 1. Schema of STM systems Short Term Memory Sensory buffers Working memory Sensory cortices Prefrontal cortex

20. 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

21. LTM declarative systems Long term memory Declarative (explicit,items)) Non-declarative (implicit skills, etc) Episodic (individual) Semantic (knowledge) Several subtypes

22. 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

23. 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

24. 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

25. Executive SkillsPart 2 Puja Patel Seminar in Developmental Disabilities March 20, 2013 No conflict of interest