Cortico-motor pathway and motor plasticity

Question 1

Cerebral cortex, motor areas:

Answer 1

Premotor cortex

Planning and initiation of voluntary movement

Question 2

Sensory motor

Answer 2

integration & learning

Question 3

brain stem

Answer 3

Basic movement & posture

Question 4

reflex

Answer 4

• spinal cord

involuntary movement

Question 5

The corticospinal tract

Answer 5

upper motor neurons

motor cortex > anterior horn of sc

Question 6

The corticospinal tract

Answer 6

Direct pathway from the primary motor cortex to the spinal cord
- 75-90% of the axons cross over to the opposite side of the CNS in the medulla (referred to as pyramids)
• Lateralcortico-spinaltractorlateral pyramidal tract
• Essential for the fine movements of distal extremities (limbs)
10-25% don’t cross over
• Anterior corticospinal tract or anterior pyramidal tract
• Innervate axial motorneurons
• Some innervate bilaterally (neat for bilateral tasks, walking etc)

Question 7

Parallel Processing

Answer 7

• Simultaneous transmission of the same general type of information along separate neural pathways
– Corticospinalandcorticobulbar
• If a corticospinal pathway was damaged, the corticobulbar system can partially compensate so that some movements are not entirely lost

Question 8

Primary Motor Cortex

Answer 8

– initiation and execution of motor plans by developing a program of commands for lower motor neurons. 60% of upper motor neurons originate here.

Question 9

Premotor Cortices

Answer 9

• responsible for planning and selecting complex movements. Also has a role in postural preparation prior to an event and processing visual information.

Question 10

Supplementary Motor Area

Answer 10

provides a plan that specifies the sequence and extent of muscle contractions needed to execute a movement.

Question 11

Posterior Parietal Cortex –

Answer 11

takes in sensory information and forms a conscious map of the body and its relationship with its surroundings.

Question 12

cortical control of mvmt

Answer 12

Flexing the finger – M1 only
Writing a letter with finger (complex sequence of movement)
– M1, premotor and supplementary cortex Think about writing with the finger
- premotor and supplementary cortex, not M1.

Question 13

The somatotopic map

Answer 13

in primary motor cortex
Disproportionally large representation of parts requiring greater precision control
Somatotopic maps also exist in premotor cortex & supplementary motor cortex
- Deprivation causes reduction of representation
evidenced by Functional Magnetic Resonance Imaging (fMRI), electrical -
http://www.martinos.org/neurorecovery/technology.htm
Brain stimulation Electrical /magnetic
Intracortical stimulation and magnetic techniques - Transcranial Magnetic Stimulation

Question 14

Effect of voluntary contraction

Answer 14

Muscle contraction is associated with increased corticospinal excitability at spinal and cortical level
Observed as an increase in MEP amplitude following a TMS pulse

Question 15

The type of training is important

Answer 15

Complex skill learning - Corticospinal excitability i.e. MEP amplitude increase
Strength training - no change
no training - no change

Question 16

Pain and motor plasticity

Answer 16

Authors concluded that pain reduced ability to learn a new motor task (i.e. increase cortico-motor excitability).

1) Decreased ability to perform task
2) Altered attention to task due to pain

Question 17

back pain

Answer 17

Chronic low back pain is associated with altered trunk muscle coordination

• Training can improve motor behaviour
• Improvement in motor performance was related to a return to normal brain map of trunk muscles