Reaction to removal of a digit the maps of digit 2

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Reaction to removal of a digit The maps of Digit 2 and Digit 4 have sprouted to take the place of Digit 3 Collateral Sprouting input 1 & 2 both send signals to soma if you cut input 2, input 1 grows new connections to send signals to axon Phantom Limbs Case: guy lost limb next to his elbow Felt his arm moving to grab an object – why? Still has representation in the brain and in
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upper shoulder/arm Why would you feel the hand representation on face/arm? Order in homunculus Phantom Limb Pain Lost arm/hand but feels pain from clenching fist still has motor command in brain (clench my fist) but don't have feedback to stop Mirror box fools your brain that your limb exists visual feedback instead of somatosensory feedback practice and can stop phantom pain V. Beyond Somatosensation Dorsal and ventral streams leading FROM primary visual cortex: Dorsal: to parietal lobes Ventral: to temporal lobes Egocentric space – the world is orientated entirely on one's body position dorsal stream Allocentric space – map of the world based independent of body position – position of objects in relation to one another memory of space/relationships between objects (long-term storage) ventral stream Posterior parietal cortex all the information comes together Hemi-Neglect holes in egocentric space damage to right posterior parietal cortex vs. damage to left posterior parietal cortex right: gestalt representation of left and right side of the world left: only processes right side of the world don't see hemi-neglect when you damage left posterior parietal cortex right can visualize right side of the world “real space” - instantaneous map of egocentric space continually updated – changes every millisecond November 30, 2012: Motor 1993 study put into a PET scan asked to tap finger primary motor cortex lit up asked to do a motor sequence premotor cortex and primary motor cortex lit up asked to follow a route prefrontal cortex, premotor cortex, and primary motor cortex lit up Sensor and Motor Homunculus part of your body that needs the greater dexterity have the largest components in homunculus Neurons in M1 Specify Movement, Force and Direction 1982 study before movement neuron fires → anticipation need to figure out motor sequence – what muscles do I need to move this rod?
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during movement greater weight = more firing from cells → cell's responding to force required to move rod Corticospinal tract Down from cortex → midbrain → middle pons → middle medulla -. Caudal medulla → spinal cord aka “pyramidal tract” damage results in paralysis Motor Systems 1. Pyramidal system corticospinal tract motor cortex voluntary movements 2. Extrapyramidal system Midbrain nuclei basal ganglia inhibits unwanted movements movement initiation maintains muscle tone and trunk stability (posture)
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