lecture 20: somatosensation and motor control

Question 1

forebrain: initiating movement

Answer 1

lashley: perform skilled movements too quickly to rely on feedback about movements so they must be preformed as motor seqeuences with next sequence held in readiness

Question 2

motor sequence

Answer 2

movement module preprogrammed by brain and prdocued as a unit

Question 3

frontal lobes

Answer 3

initiate most voluntary motor behavior:
- prefrontal cortex –> plans complex behavior
premotor cortex–> organizes and coordinates complex sequences
primary motor cortex–> produces focal skilled movements

Question 4

damage to premotor cortex

Answer 4

cannot put motor sequences together
- cant push through with 1 finger and catch it
cannot coordinate movement

Question 5

primary motor cortex function

Answer 5

producing focal skilled movements ex. arms, hands and mouth

- damage to M1 shows difficulty reaching and shaping fingers to perform various hand grasps

Question 6

brainstem: species-typical movement

Answer 6

hess:

• stumlate diff areas of brainstem and produce species typical behaviors
  1. brainstem controls
  2. species typical behaviors are complex and coordinated
  3. behaviors are adaptive: vary with context

Question 7

species typical behavior

Answer 7

actions produced by every member of species

ex. whales breaching

Question 8

spinal cord: executing movement

Answer 8

SC executes complex movements w/o brain
ex. scratching, walking, reflexes
damageL quad/paraplegia

Question 9

motor homonculus

Answer 9

spatial represnetation of body in motor cortex
distorted by: size of representation and discontinuous
- represents repertoire of fundamental movement categories similar to language

Question 10

role of motor cortex neurons

Answer 10

plan and initiate movements
exxecut emovement
code force of movement
movement position
- subthreshold activity in MC may underlie ability to imagine movement

Question 11

plasticity in MC

Answer 11

without: hand area becomes smaller and elbow/shoulder larger
with: hand area retains size and retain some ability to move hand
constraint: forces use of affected limb in stroke induced limb paralysis

Question 12

corticospinal tract: MC to muscle

Answer 12

main descending pathway from motor cortex (efferent)

• descend into BS
• emerge on ventral surface to form pyramidal tract where axons dessucate

Question 13

2 descending paths of CS tract

Answer 13

lateral: decussates at brainstem, moves digits/limbs
(extremeties, contralateral)
ventral/anterior: same side of brain, moves midline on same side of body (trunk/ipsilateral)

Question 14

CS in spinal cord

Answer 14

terminate in spinal cord

• synapses with interneurons and motor neurons
• motor neurons carry commands to muscles

Question 15

basal ganglia

Answer 15

subserve wide range of functions, association or habit learning, motivation, emotion, motor control
input from neocortex and dopaminergic system from substantia nigra
project back to motor cortex (recipricol loop)

Question 16

hyperkinetic disorders

Answer 16

striatum damage causes unwanted writhering twitching movements and too much force (huntingtons, tourettes)

Question 17

hypokinetic disorders

Answer 17

damage to basal ganglia leads to loss of motor ability, rigidity, trouble initiating / producing movements, not enough force (parkinsons)

Question 18

volume hypothesis

Answer 18

internal globus pallidus (GPi) acts like a volume control on motor cortex: turned up = movement blocked, turned down = movement allowed

direct: inhibited GPi and produces movement
indirect: activated GPi and blocks movement

Question 19

cerebellum

Answer 19

involved in refined execution and timing of movement

lobes: anterior, posterior, flocculur
hemispheres: homuncular organization, lateral (limbs, hands, feet), medial (face and midline of body)

Question 20

experimental clues to cerebellums role

Answer 20

1. cerebllar patients and movement corrections: many movements require rapid updating and correction from cerebellum
2. monkeys trained to point with/without prism glasses , learned adaption in long term motor learning
   - cerebellum compares intended movement with actual movement and reports errors for correction