Motor Systems 1 - Ebner

Question 1

What sorts of motor deficits accompany problems in the motor cortical areas?

Answer 1

Loss of voluntary movement
Paresis
Increased tone
Increased stretch reflex

Question 2

Are the motor cortical areas responsible for internally or externally generated movements?

Answer 2

Internally generated movements

Question 3

What is the cytoarchitectual and stimulation criteria required to be considered a MOTOR CORTICAL AREA?

Answer 3

Cytoarchitecture:
-Agranular
poorly developed granular layers
well developed pyramidal layers

Stimulation Criteria
-Evoke movements at low stimulus intensities

Question 4

What is the afferent innervation to the primary motor cortex?

Answer 4

1. Afferent input from periphery via dorsal column nuclei (DCN) and thalamus (VPL)
   a. Joints
   b. muscle spindles
   c. cutaneous skin
2. Cerebellum and basal ganglia
3. Cortical inputs to area 4
   a. Somatosensory cortex
   b. Premotor cortex
   c. Supplementary motor area
   d. Posterior parietal cortex (Areas 5 and 7)

Question 5

What percent of the output projects come from Giant Betz cells in the primary motor cortex?

Answer 5

Only about 3%

Question 6

Ouput projections from the motor cortical areas come from what types of neurons?

Answer 6

Pyramidal cells

Question 7

Most of the corticobulbar tract innervates bilaterally. What is the exception?
What are the slight exceptions?

Answer 7

Lower half of face -contralateral motor cortex ONLY

Spinal Accessory - slightly more ipsilateral

Hypoglossal - slightly more contralateral

Question 8

Where do the frontal eye fields project to?

Answer 8

Projects to brainstem gaze centers which surround and in turn project to cranial nerve nuclei III, IV and VI

Question 9

The corticospinal tract terminates in what part of the spinal cord?
Why?

Answer 9

If you said Ventral Horn - you are only partly right
They also terminate in the dorsal horn and intermediate gray.

They do this because they actually have the ability to help control sensory info coming through these areas.

Question 10

How did the monkey pulling their wrist against a load prove that cells can encode force?

Answer 10

Recording electrode showed that neurons fire with greater frequency before, during, and after a movement is made with greater force

Question 11

What is population code with regard to neurons? How is this functionally important for the nervous system?

Answer 11

A large amount of neurons are broadly tuned to a kind of movement, they all fire and contribute to that movement when the time comes. They can fire more or less depending on how closely the movement corresponds to the neuron’s “preference” (direction preference for example)

This makes the movements immune from the fluctuations that would exist if a single neuron were responsible for one very specific movement

Question 12

How is population code relevant clinically?

Answer 12

Scientists have been able to trace these population codes in order to try to stimulate controlled movement in prosthesis!