Supplementary and pre motor areas

Question 1

where are the SMA and PMA located

Answer 1

frontal lobe
rostral to M1

Question 2

what are the 3 functionally distinct areas in the SMA and PMA

Answer 2

dorsal pre motor area (PMd)
ventral pre motor area (PMv)
supplementary motor area (SMA)

Question 3

function of dorsal pre motor area (PMd)

Answer 3

planning and selection of goal directed voluntary mvmts
somatosensory feedback during ongoing mvmts

Question 4

function of ventral pre motor area (PMv)

Answer 4

somatosensory, visual, auditory feedback during mvmts
hand shape for grasping, aligning the hand and mouth

Question 5

function of supplementary motor area (SMA)

Answer 5

important for planning and selecting sequences of self initiated voluntary actions

Question 6

what are the inputs into the SMA and PMA (3)

Answer 6

prefrontal cortex (PFC)
- selecting and planning voluntary motor actions
S1
- somatosensory feedback for the selection and guidance of motor actions
posterior parietal cortex (PPC)
- somatosensory and visual feedback for selection and guidance of motor actions

Question 7

what is the somatotopic organisation of the SMA and PMA

Answer 7

more overlap in the representation of body areas compared to M1 and S1

Question 8

what are the two main outputs from SMA and PMAs

Answer 8

outputs to cortical and subcortical structures

Question 9

what are the ouputs to cortical structures responsible for

Answer 9

M1
- selection, planning, and initiation of a specific motor action amongst possible alternatives
PPC
- influence the processing and integration of somatosensory and visaul feedback during ongoing actions

Question 10

what are the ouputs to subcortical structures responsible for

Answer 10

descending motor tracts
- to initiate and control voluntary motor actions (CSTs)
nuclei in basal ganglia and thalamus
- recurrent connections influence ongoing porcessing in the motor and PMA (basal ganglia-thalamocortical circuit)

connections are limited compared to projections from M1

Question 11

what is the role of PMv (ventral pre motor area)

Answer 11

involved in the shaping of the hand for grasping mvmts

Question 12

what are the two types of neurons present in the PMv

Answer 12

canonical PMv neurons
mirror neurons

Question 13

what is the function of canonical neurons

Answer 13

respond to the presentation of an object
sensitive to object change and encode object shape for grasping
represent overall goal of action

Question 14

what / when are canonical neurons sensitive

Answer 14

sensitive to goal of performing a precision grip regardless of whether it is performed with the left or right hand
- firing rate is slightly better when its performed with the contralateral hand
different neurons are sensitive to every type of grip and different postures / configurations of hands

Question 15

what is the function of mirror neurons in the PMv

Answer 15

represent the overall goal of action
- selectively respond to different types of arm and hand mvmts regardless of whether the mvmts are performed by the subject or by watching someone else

Question 16

what is the role of PMd (dorsal pre motor area)

Answer 16

selecting and planning motor mvmts
- selecting and performing and action when there are several alternatives
- also processes sensory feedback during ongoing voluntary actions

Question 17

what is the function of neurons in the PMd

Answer 17

neurons have a preferred direction (max activity)
- potential target locations are encoded in rostral PMd (less in caudal PMd)

Question 18

what is the difference between rostral and caudal PMd neurons

Answer 18

rostral = encodes potential action alternatives
rostral and caudal = plan and control ongoing reaching mvmts

Question 19

what are some of the lesser functions of the PMd

Answer 19

performing and simulating motor actions
important for simulating goal directed motor actions

Question 20

when is the PMd active

Answer 20

engaged in task regardless of whether action is performed or not
same preferred direction for action and observe only conditions
neuron fires when a reaching or observing a target in its preferred direction and inhibits firing when in anti preferred direction

Question 21

what is the function of the SMA (supplementary motor area)

Answer 21

selecting and executing self generating voluntary actions
- contrast with stimulus driven actions
postural stabilisation
- shifts in balance preceding voluntary mvmts
bimanual action
- coordinating mvmts of two arms

Question 22

what is the activity of SMA neurons

Answer 22

show selective activity when preparing for and performing familiar learned actions
- show little to no activity when performing unfamiliar sequences

Question 23

what occurs with damage to SMA

Answer 23

alien hand syndrome
- hand would hit and remove items from bag and throw them (involuntary)