Motor Control

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Motor Control
2011-05-02 13:49:10

Chapter 7
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  1. Endpoint Control, Bizzi Experiment (pg 268)
    showed that central representations can be based on LOCATION code; deafferented monkeys were trained to move their arm to a target (light); the experiment was that they put these monkeys in the dark and did two trials, one where the monkey simply had to make the movement and the other where there was some opposing torque at the START of the movement, which was lifted after about a second; if the trajectory plan of movement was true, it would appear that the monkeys would overshoot their goal after the torque was removed, but they didn't, they still landed on the target
  2. endpoint control
    a hypothesis concerning how movements are planned in terms of the desired final location; endpoint control models emphasize that the motor representation is based on the final position required of the limbs to achieve the movement goal
  3. primary motor cortex (M1) [broadmann's area 4]
    region of the cerebral cortex that lies along the anterior bank of the central sulcus & precentral gyrus; some axons originating here form the majority of the corticospinal tract while others project to cortical and subcortical regions involved in motor control; contains a priminent somatotopic representation of the body
  4. memorize these dummy
  5. apractognosia
    disorder that consists of several apraxic and agnostic syndromes stemming from an impairment of spatial perception; due to lesions of the minor cerebral hemisphere?
  6. Somatotopic Organization of Primary Motor Cortex
    exquisite control of face and hands; ex: making sounds; organization is not as clean as you would imagine; even less clear in premotor cortex
  7. Graziano
    generated (by using more current for longer) different patterns of activity in monkeys; behavioral movements that appear to be meaningful – not just twitches; interface between face and hand representation: the monkey will bring his hand to his mouth and open his mouth (as if he’s invoked feeding movements); some areas are defensive/protective evoked gestures; recording from these cells: the activity in cells match when the animal does the movement on it’s own or when it’s stimulated
  8. Georgeopoulos center-out task
    monkeys with stickshifts; end result is that this specific neuron is most active for movements in the DOWNWARD (or toward) direction, no matter what the starting/final locations were, therefore cells in the motor cortex are more important for movement direction rather than target location
  9. population vector
    a cortical representation of movement; direction of a vector is ALWAYS plotted as the neuron's preferred direction, and the length corresponds to it's firing rate for a specified direction; provides a better correlation with behavior than recordings from an individual neuron
  10. Moran & Schwartz, as well as the Brain Machine Interface show:
    that the muscle pattern is somewhat identical to the neural pattern, therefore one can predict the other
  11. Brain Machine Interface
    electrical system controled only by the brain, no muscle movement is made; in addition control improves with practice/time as the neruons' spatial tuning properties change; ex: seen with the monkey and the marshmallow, robotic hand
  12. phantom limb mirror box
    besides how cool it is, the relief recieved when using the box and actual hand relieved tension from the phantom hand gives insights into how closely the visual system is intertwined with motor system
  13. MRI studies of the mirror box show....
    when looking in the mirror box and clenching/unclenching there's activity in the side of the brain that would correspond to the amputated limb; patterns like this indicate there’s more to motor areas that simply descending neurons going to spinal chord to effectors; motor system is not SIMPLY output areas
  14. Graziano Spatial Coordinates Study Showed:
    that some neurons in the basal ganglia would be useful for coordinating visually guided movement; the recorded neuron's receptive field shifts with the movement of the monkeys hand; when the hand's out of sight, the neuron doesn't fire;
  15. egocentric framework
    where something is in relation to myself; related to Graziano's study
  16. Goodale and Milner: ‘what’ & ‘where’ pathway
    said the ventral stream served to process visaul information to perceive things out there, and that the dorsal stream was vision for action; involves space, in a way that was useful for using vision to guide actions
  17. LIP
    contains a map of potential/planned saccade goals
  18. MIP (medial intraparietal region)
    basically MIP contains a map of potential arm reach goals; has cells that show that represent immediate external space (aka very near region you can reach to)
  19. AIP (anterior intraparietal region)
    contains a map not of the location but of shape information needed to grasp objects; represent shape/other characteristics of an object about to be interacted with
  20. VIP (ventral intraparietal region)
    represents ultra near space used to guide head, mouth, and lips during feeding; makes sense that a VENTRAL area would control that because visual information isn't needed as much as tactile/spatial for things like feeding
  21. Rizzolatti: Mirror Neurons in PMv (F5)
    found that neurons in this area fired both when the monkeys were moving their hands or mouths and when they were simply watching another animal or human perform the same task; F5 is analogous to human's Brocca's area
  22. canonical neurons
    become activated when you merely see an object that can be grasped by the prehensile movement of the hand whose movements they encode—as if the brain were foreseeing a possible interaction with this object and preparing itself accordingly