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Cogsci/Psychology 127: Lecture 12 Cortical Representation of Action

Cogsci/Psychology 127: Lecture 12 Cortical Representation of Action. Clarification of Apraxia Ideomotor apraxia: Difficulty in carrying out commands, producing coherent actions, esp. with sequential actions.

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Cogsci/Psychology 127: Lecture 12 Cortical Representation of Action

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  1. Cogsci/Psychology 127: Lecture 12 Cortical Representation of Action

  2. Clarification of Apraxia Ideomotor apraxia: Difficulty in carrying out commands, producing coherent actions, esp. with sequential actions. Ideational apraxia: Loss of knowledge about actions and how they are used to manipulate objects. Parallel to distinction between apperceptive and associative agnosia. Associative agnosia and ideational involve loss of functional knowledge. Both associated with left hemisphere damage.

  3. fMRI activation during planned tool use Right Hand Movement Left Hand Movement Left hemisphere asymmetry for either hands. Dorsal and ventral extension. Clinical predictions?

  4. Neural Code of Action in Motor Cortex: Directional tuning of single cells.

  5. Neural Code of Action in Motor Cortex: Directional tuning of single cells. What is being coded?

  6. Preferred direction is usually confounded with muscle activity. Direction: External reference frame Muscle: Internal reference frame Method to test if representation is direction or muscle.

  7. Direction and muscle representations are found in primary motor cortex Cell A: Muscle-based Cell B: Direction Based

  8. Neural Region Computation Motor Cortex Simple Movements codes in terms of muscles, movement direction

  9. Premotor cortex and SMA: Fewer cells are muscle-based. Cellular activity is sequence dependent. Link of simple gestures into more complex representations.

  10. TMS during Movement Sequences Train with movement sequences: 1-4-3-2-1-3-4-2 TMS at various points (high frequency for 2 s) SMA Stimulation Motor Cortex Stimulation

  11. Range over which errors occurred after TMS SMA: “I forgot where I was in the sequence” MC: “My hand got stuck.”

  12. Neural Region Computation Motor Cortex Simple Movements codes in terms of muscles, movement direction SMA/Premotor Translation of goals into motor codes; Formation of stimulus-response links; Formation of sequential representations

  13. Abstract Representation of Action Goals R Hand R Wrist L Hand Mouth R Foot

  14. Neural Representation of Action Goals Repeated movements vs. repeated outcomes (goals) Movements: push or pull Outcome: open or close

  15. Neural Representation of Action Goals Repeated movements vs. repeated outcomes (goals) Movements: push or pull Outcome: open or close Repetition Suppression Effect: Reduced BOLD response as neural marker of consistency in representation.

  16. Neural Representation of Action Goals Repeated movements vs. repeated outcomes (goals) Movements: push or pull Outcome: open or close Repetition Suppression Effect: Parietal areas showing reduced BOLD when goal remains same.

  17. Neural Region Computation Motor Cortex Simple Movements codes in terms of muscles, movement direction SMA/Premotor Translation of goals into motor codes; Formation of stimulus-response links; Formation of sequential representations Parietal Abstract representations of action goals.

  18. Goal-directed reaching… Parietal: Use spatial information to develop action goal. Premotor: Translate goal into movement path/sequence. Motor: Translate movement path/sequence into motor commands. Spinal: Activate muscles.

  19. Goal-directed reaching… …without arm movement? Parietal: Use spatial information to develop action goal. Premotor: Translate goal into sequential movement path. Motor: Translate movement path into motor commands. Spinal: Activate muscles.

  20. Neuroprosthetics: Brain-Machine Interface (BMI) Systems Decode neural signals to control prosthetic limbs. Visual input

  21. Population Vector Describes representation across many neurons. Movement of animal is function of summed activity over all of the cells. % of maximal activity Preferred Movement Direction Direction of Cell Right Down Left Cell 1 Right 80% 40% 40% Cell 2 Left 10% 50% 80% Cell 3 Down 40% 90% 40%

  22. First generation Brain Machine Interface (BMI) Population vector derived from 24 cells is used to drive lever.

  23. Second Generation BMI: 2-d Movements Train with monkey using mouse-like device to move cursor while recording from motor cortex neurons. Test with cursor driven by population vector constructed on-line from neural signals. Donoghue Movie (monkey_cursor_control) NOTE: Animal sometimes moves, sometimes doesn’t.

  24. Second Generation BMI: 2-d Movements Train with monkey making reaching movements while recording from premotor cortex neurons. Representation is more location/goal based. Test with cursor driven by population vector constructed on-line from goal-based signals. Shenoy movies (delayed reach, medium and fast speed): Train and record, then BMI control Delay: Animal moves when target expands. Medium, Fast: BMI to small. Reach to large. Needed to keep monkey focused.

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