control of somatosensory feedback (goal directed actions)

Question 1

what is the cuneate fascicle

Answer 1

carries sensory info from the upper body and trunk
- at or above T6
- more white matter - more info being routed to the brain with less spinal processing

Question 2

what is the gracile fascicle

Answer 2

carries sensory info from the lower limbs and trunk
- only gracile present below T6
- more grey matter and less white matter (more spinal processing)

Question 3

what is the organisation of the fascicles in the spinal cord

Answer 3

medial to lateral = gracile to cuneate
feet = medial
hands = lateral
(think person standing in a T - move up from feet and out to hands as medial to lateral)

Question 4

where are sensory and motor neurons in the spinal cord

Answer 4

sensory neurons = dorsal horn
motor neruons = ventral horn

Question 5

what is the internal capsule

Answer 5

white matter tract that carries info from the thalamus to S1

Question 6

what is the purpose of the thalamus in this context

Answer 6

relay centre fro somatosensory info form the periphery to S1

Question 7

what is the VPMn

Answer 7

ventral posterior medial nucleus
- somatosensory info from the head, face, and neck

Question 8

what is the VPLn

Answer 8

ventral posterior lateral nucleus
- somatosensory info from the rest of the body

Question 9

what are the properties of long latency reflexes (50-105 ms post perturbation)

Answer 9

• recruit sensory and motor circuits in the brain
• show flexible goal directed processing
• slower but more functional than SLRs
• processing capabilities of LLRs depend on the task

Question 10

when do LLRs increase

Answer 10

when the goal of the task is to resist a mechanical perturbation

Question 11

where are CM cells concentrated

Answer 11

anterior (rostral) bank of the central sulcusw

Question 12

why is it useful to target CM cells to study activity in M1

Answer 12

neurons connect directly onto aMNs
- don’t have to worry about interneurons

Question 13

what is the initial response when asked to push or pull the handle, regardless of anything else

Answer 13

initial excitatory response regardless of perturbation and then M1 neurons show rapid, goal directed responses

Question 14

what is the response when the perturbation is opposite to the goal

Answer 14

clear sustained activity until the hand enters the target
fires until the goal is obtained and then stops firing

Question 15

what is the response when the perturbation is in the same direction as the goal

Answer 15

neuron shuts off until the hand enters the target
resumes low level background activity

Question 16

what does the posture control vs movie task examine

Answer 16

how the task goal influences the time course of somatosensory processing and resulting perturbation responses

Question 17

what is the order in which areas respond to somatosensory feedback

Answer 17

1. S1
2. area 2
3. area 5 (parietal)
4. M1
5. PMd (dorsal premotor)

Question 18

what does the order in which brain areas are activated correspond to

Answer 18

the order the brain areas receive somatosensory feedback from the periphery

Question 19

what is the order in which areas respond to somatosensory feedback in a task dependent way (show goal directed response)

Answer 19

1. area 5
2. M1
3. S1 (area 3a)
4. PMd
5. area 2

Question 20

why is area 5 the first area to respond in a task dependent way

Answer 20

responds quickly because it’s activity often depends on the goal
- important in attention

Question 21

why is M1 faster at responding in a task dependent way than S1

Answer 21

info travels from area 5 to M1 directly
- generates a motor command that is different for different goals

Question 22

what is the role of S1 in task dependent responses

Answer 22

responds to feedback and the feedback differs depending on the mvmt

Question 23

how can the onset of task directed processing be revealed

Answer 23

subtract the default perturbation response in posture task from the goal directed response

Question 24

what is the differences between the posture control task and movie task

Answer 24

posture control
- hand perturbed from green target and need to get back within a certain amount of time
- need to respond quick for reward

movie task
- reward regardless of response to perturbation
- elicits no response (or very little)

Question 25

what is the functional anatomy of the cerebellum

Answer 25

symmetrical - 2 hemispheres 3 sets of deep cerebellar nuclei fractured somatotopy (all areas are recognised but not organised)

Question 26

what does the spinocerebellum contain

Answer 26

vermis and intermediate hemispheres

Question 27

which deep cerebellar nuclei are in the spinocerebellum

Answer 27

fastigial nucleus (vermis) interposed nuclei (intermediate hemispheres)

Question 28

what does the cerebrocerebellum contain and what is its function

Answer 28

lateral hemispheres higher level, goal directed processing

Question 29

which deep cerebellar nuclei are in the cerebrocerebellum

Answer 29

dentate nuclei

Question 30

what is the effect of a cryoloop

Answer 30

causes reversible focal inactivation by lowering tissue temp until neurons stop firing (~21 C) - changes the neurons excitability by changing the ion concen - used to assess how the brain areas contribute to behaviour

Question 31

what was the purpose of cryoprobes in the cooling experiment with monkeys

Answer 31

enable direct control of the function of the interposed and dentate nuclei to quantify impact on behaviour

Question 32

what was the impact of cerebellar cooling on perturbation responses

Answer 32

interferes with sensory processing and begins to cause oscillatory corrective responses disrupting task behaviour (smooth correction back to postural target in absence of cooling)

Question 33

what was the impact of cooling on cortical recordings in M1 and EMG

Answer 33

- increased amplitude and improperly timed triceps (antagonist) EMG - increased oscillations - increased amplitude and phasic bursts of biceps EMG - increased amplitude and phasic bursts of M1 neuron

Question 34

are the behaviour impairments caused by proprioception or vision deficits

Answer 34

proprioception - oscillations, and improperly timed and scaled responses are seen in vision and no vision conditions (doesn't matter if vision is present or not because it's so slow to process feedback)

Question 35

where are electrodes placed for stimulas and instruction dependent activity in the cerebellum

Answer 35

interposed and dentate nuclei

Question 36

what do interposed nuclei process

Answer 36

process sensory feedback (don't reflect the goal)

Question 37

what do interposed nuclei respond to

Answer 37

direction of motion (inhibited during opposite direction) - have a preferred direction - sensitive to motion but not the goal

Question 38

what do dentate nuclei process

Answer 38

higher level processing process feedback in a goal directed way - sensitive to task instruction

Question 39

what do dentate nuclei respond to

Answer 39

goal of the task - responds or inhibited based on the goal regardless of the direction / perturbation doesn't respond to direction of motion

Question 40

what is the effect of cooling PMd on task performance

Answer 40

- hand displaced further - hand returns slower - larger endpoint errors (deviations increase as cooling continues)

Question 41

what is the effect of cooling area 5 on task performance

Answer 41

- respond more vigoursly - hand displaced less than baseline - hand returns faster - displays larger endpoint errors

Question 42

are neural responses in M1 larger when the hand is bumped towards or away from the target

Answer 42

larger when bumped away

Question 43

when do goal related difference in M1 processing emerge

Answer 43

50-60ms after perturbation

Question 44

why are there different responses before the perturbation is turned on

Answer 44

differences in set up allow for pre planning - neurons that are sensitive in that direction can fire more APs

Question 45

why does it show potential that goal directed processing can happen outside M1

Answer 45

if everything happened in M1, the neural response lines shoudl be separate the whole way

Question 46

are EMG responses larger when the hand is pumped away or towards the target

Answer 46

larger when bumped away

Question 47

when do goal related differences in EMG emerge

Answer 47

60-70ms after perturbation - after M1 burst of activity