Supplementary motor area (SMA) and premotor cortex (PM)

Question 1

supplementary motor area (SMA)

Answer 1

• direct projections (~10%) to spinal cord and cortico-cortico connections to M1
• different projections to spinal cord terminate on a-motorneurons that innervate hand musculature
• squence-specific
• active for internally generated movements
• activity increases with movement complexity
• active for real and “imagined” movements

Question 2

premotor cortex

Answer 2

• fewer direct projections (~10%) to spinal cord than SMA
• strong connections with subcortical structures (i.e. cerebellum)
• triggered by external sensory events and delayed action
• PMA important for: obstacle avoidance and perseveration behaviours

Question 3

M1, SMA and PMA

Answer 3

• finger sequencing task on monkeys

M1: visual task: increase neuron activity; internal condition: increase neuron activity

SMA: visual: no change; internal: increase

PMA: visual: increase; internal: no change

• specialised roles, SMA - internal movements, PMA - movements triggered by visual stimuli

Question 4

mirror neurons

Answer 4

• monkey watches another monkey grasp a peanut, a human grasp a peanut and the monkey grasp a peanut
• the specific neurons were activated on all three experiments

Question 5

mirror neuron network

Answer 5

Mirror neurons are known to be associated with 4 areas:

SMA - supplementary motor area

VPMA - ventral premotor area

S1 - primary somatosensory cortex

IPC - inferior parietal cortex