Lecture 17 - cortical contributions to movement

Question 1

Describe the primary motor cortex.

Answer 1

• located anteriorly to the central sulcus
• associated with voluntary movements
• neurons in m1 modulate their activity prior to movement
• how much neurons fire can be related to the force exerted during the movement

Question 2

What is used to activate the motor cortex non-invasively?

Answer 2

transcranial magnetic stimulation

Question 3

What is the pegboard task?

Answer 3

• involves the subject has to pick up pegs and put them in holes
• measure how long this takes
• can compare between affected and non-affected sides of the brain

Question 4

What results are shown in the peg-board task when there is a lesion to the motor cortical region?

Answer 4

• reduced movement speed
• reduced accuracy
• abberant muscle synergies
• muscle weakness

Question 5

What are the 3 secondary motor areas?

Answer 5

1. premotor cortex
2. supplementary motor area
3. cingulate cortex
   - these areas send projections to M1

Question 6

Neural activity in different motor areas - describe what happens in M1.

Answer 6

• the neuron shows very similar responses in both of the trials as motor output is the same

Question 7

Neural activity in different motor areas - describe what happens in the lateral premotor cortex.

Answer 7

• the neuron fires before the movement only in the visually triggered activity

Question 8

Neural activity in different motor areas - describe what happens in the SMA.

Answer 8

• the inverse result
• SMA neuron is much more active around the time of movement for internally triggered trials than visually triggered trials

Question 9

Bimanual movements - describe the results.

Answer 9

• left motor cortex is very active in movements of the right hand and both hands but does not show activity of the left hand
• SMA has neurons that are active during the movement of the right hand and won’t fire when the left hand or both hands are used
• the SMA has neurons that fire when either the left or right is used but not when both are used
• SMA more sensitive to bimanual nature of movements

Question 10

What are mirror neurons?

Answer 10

• active when an animal does a task
• the same neurons are active when the animal observes another animal or even human doing the same task
• more common in the premotor cortex

Question 11

What is alien hand syndrome?

Answer 11

an elaborate deficit following a lesion in the SMA and corpus colosseum. purposeful and autonomous movements that are not voluntary initiated by the patient.

Question 12

Where is the somatosensory system located?

Answer 12

behind the motor cortex on the other side of the central sulcus

Question 13

What is the corticospinal system?

Answer 13

the direct line for communication from cortex to the spinal cord

Question 14

What is the corticospinal system made up of?

Answer 14

• neurons projecting from several different areas
• M1 is the biggest contributor
• SMA contributes about 30% of the fibres
• the remaining 30% of fibres comes form the somatosensory areas

Question 15

What type of termination pattern correlates with improved fine motor control?

Answer 15

ventral termination pattern

Question 16

Describe corticomotoneuronal connections and manual dexterity.

Answer 16

as index of dexterity increases so does the strength of the connection to motor neurons
the lack of this connection in rodents blocks it from being used for research purposes in these experiments