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Andy Lee (27)

PSYC55 lec 3 jan 24.docx

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Andy Lee

PSYC55 – lec 3 Jan 24h Motor control: hieracrchical organization - Cerebellum and basal ganglia (subcortical regions) are heavily involved in feedback and adjusting motor - Motor cortex is most critical region for motor movements and output is most - Finer the movement, the greater the representation within motor cortex - Middle cerebral artery strokes cause most problems with motor cortex o Even if motor cortex is lesioned, reflexive movement is generally intact or even hyperactive o Motor cortex very important for voluntary movements, not involuntary - ** research on Georgopoulous experiment with motor cortex. Recorded for motor neurons as the monkeys are moving hte aactual joystick o More actionpotentials, more active cell, that’s where monkey is pointing? o Make a tuning curve for all directions o This cell responds the most when monkey is moving in 180 degrees towards the left. Meaning this is the preferred durectuin for the cell . o Each individual cell is directionally sensitive, codes movement in only one direction o All cells within same column all have the same selective direction o If you move across columns, you see the directional sensitivity shifts in a systematic way. Slight shift as you move columns across o The cell still does fire in other directions though, but most to a particular direction. Wide ranging tuning curve o Two cells with different preferred directions firing at the same time  you sum the vectors and you get an averaged direction. The weight of the direction depends on amount of firing from the cell o Whiel they were asking monkeys to move in different directions, the movement was confounded with muscle patterns  Unclear whether neurons are just coding direction of movement, or muscle contration  Kakei: instead of arm movement, move the wrist only. o In motor cortex, some neurons fire for muscle some do for direction o In the premotor cortex, they fire just for direction o Example of hierarchy: premotor is just direction, motor is also interested in execution of movement - PMC and SMA: critical for planning and sending signals for executing action, stimuli and sleecting correct movement to make o The closer the dots, more action potentials firing o Same movement , but different goals o Premotor cortex cells can be selective for the goal o This cell fires more when grasping the food, an d less when pushing it away o Goal encoding within the premotor cortex o Mirror neuron: firing to mirror actions (observing the hands). Significant firing within premotor cortex in mirror neurons. (A when experimentor is doing it, and B when monkey is doing it)  In humans too. Kilner  Significant difference within actual action executed and then when observing. Very little evidence . controversy  In monkeys, very fine movements will be mirrored in the mirror neurons - Distinction between PMS and SMA maybe the stimulus. SMA is internally guided and PMC is externally guided o Prefrontal cortex is cognitive control and goals are represented and formulated here. SMA receives alot of input from prefrontal cortex. This is why it is guided by internal cortex o Mushiake (in textbook) o PET: more blood flow there, more activity  Finger movements learned before into scanner (internal) or learned new pattern in scanner (external)  ‘b’ SMA more activated. Area black at the top  ‘a’ PMC more activated on black right side of pi
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