1. MSc CogNeuro Lecture 1-2: Intro + Primary Motor Cortex (MI) www.psychol.ucl.ac.uk/patrick.haggard/MSC/msc_1.ppt

2. Action Behaviour Movement Cognition Survival

3. Brain control to action Not conscious Computational processes Learning

4. Computational process VolitionI want to do X SelectionHow will I do X? InitiationStart to do X ExecutionMovement towards… MonitoringHave I got there yet… StoppingDeactivate X NOTE: Process is serial, hierarchical, and information expansion

5. Computational model of action control (Blakemore, Wolpert, Frith, Trends in Cognitive Science, 2002) Planner (Inverse model) motor command Limb Goal/ Intention Forward model efference copy sensory feedback

6. Provisional Road Map (PH) A backwards hierarchy –(Muscle) –Primary motor cortex –Premotor cortex (preparation) –Supplementary motor area (physiology, psychology) –Basal Ganglia (physiology, neurology) –Cerebellum (physiology, neurology) –Cortical association circuits (somatosensory, social)

11. Primary motor cortex (MI)

12. Layered structure of cortex Descending output from layer 5 (pronounced in cortex) Layer 4 absent Betz/pyramidal cells

14. Fine-grained local somatotopy in MI is quite fractured/overlap ping Several MI zones produce same movement when stimulated Perhaps each movement is represented once for each task or synergy? We don’t know…

15. Rathelot & Strick (2006). Muscle representation in the macaque motor cortex: An anatomical perspective. PNAS, 103, 8257-8263

17. Lateral corticospinal tract (Pyramidal tract) Fine motor control of contralateral muscles Kuypers (1968) Corticomotoneuronal cell: 1 synapse from muscle - Cell body in MI, leaves via pyramidal tract

20. Lawrence & Kuypers 1968 Pyramidal tract lesion Removes key output from MI direct to muscles Lasting deficit in fine finger movement

21. Primary motor cortex code for muscle force. Evarts et al., 1968

22. Lemon 1988. Spike triggered averaging 1 MI cell contributes to force in several muscles (one- many mapping) Task-specificity 1 MI cell drives a given muscle in task A but not in task B Looks smarter than a marionette!

23. Graziano et al (2002) Micro-stimulate right M1 (and towards PMC) Long stimulation (behavioural timescale) Postures independent of start position Defensive ‘sensory-relevant’ postures

24. “Somatotopic map” is in fact a functional map of different types of manual behaviour Pro: sensorimotor transformation, motor equivalence, inverse model Con: artificial, not physiological, M1 with amputated inputs!

25. Population coding in MI? Each neuron broadly tuned for direction Multiple neurons in population Population vector predicts movement direction (Georgopoulos et al., 1998)

27. Additional topics Task specificity of MI neurons –Relation to somatotopy MI lesions in man –Hemiplegia –Psychological consequences: anosognosia for plegia Right hemisphere lesions Probably requires parietal damage also

28. Anosognosia RH damage MI AND Temporoparietal junction