motor system 3

Question 1

voluntary movements vs reflexes

Answer 1

voluntary = purposeful and allow variable response to sensory input

effectiveness of voluntary movements improve with response and initiated internally (not seen with reflexes)

Question 2

somatotopy in M1

Answer 2

homunculus just like somatosensory cortex

Question 3

microstim experiments in M1 showed
1) if stim one part

2) if provide long trains of AP

Answer 3

1) recruit muscle groups not individual muscles

2) long trains = organized movements, complex motor sequences

Question 4

describe why there is not strict somatotopy (1:1 btwn stim and muscles)

what can expand zones

Answer 4

complex mosaic of overlapping and redundant fields

allow flexibility of recruitment of multiple muscle groups for movements

practice can expand zones

Question 5

Evarts experiments for motor physiology

Answer 5

M1 neuron fired before EMG activity of extensor muscle and action

shows that activity in M1 drives movement

Microstimulation of m1 at timescales relevant to movements result in mvmts that are sequentailly distributed across multiple joints and strikingly purposeful.

Question 6

relationship of single M1 cell activity and arm movement direction

single or populations of neurons?

what is active when pointing in a given direction at level of neurons

Answer 6

Upper motor neurons of M1 cannot specify direction of movement because they are too broadly tuned.

different populations of neurons encoding net direction; single vector summation has directionality

By combining the responses of all the neurons a population vector can be computed that represents the movement direction encoded by the simultaneous activity of the entire population. = net population vector of active neurons matches movement direction

Question 7

what happens if you don’t move limb after stroke?

How to enhance recovery after stroke?

Answer 7

the initial lesion becomes worse

Constraint induced movement therapy enhances recovery after stroke (can’t use good limb and forced to use stroke side)

Use of an area extensively can lead to an enlargement of that area’s representation in primary motor cortex

Question 8

lateral premotor cortex active with

Answer 8

cue initiated movements

If you see a red stop light, premotor areas will selectively light up before M1.

Question 9

medial areas of premotor cortex active with

Answer 9

spontaneously generated movements and memory guided movements, mental rehearsal

intention of movement

Question 10

mirror neurons in premotor cortex

Answer 10

active when another person doing movement you know how to do

if you see activity in premotor doesn’t mean you actually get movement