Sensorimotor System 3

Question 1

What do long-current stimulations reveal about PMC outputs?

Answer 1

They elicit complex, natural, species-typical movement sequences rather than single muscle contractions (e.g., reaching, grasping, bringing food to the mouth).

Question 2

How is the somatotopic organization of PMC viewed currently?

Answer 2

Looser than previously thought; stimulation sites overlap across body parts, and movements are complex rather than isolated muscle contractions.

Question 3

What does overlap in PMC stimulation sites explain?

Answer 3

Why small lesions in areas like the hand region do not selectively disrupt a single finger’s activity.

Question 4

What evidence supports the endpoint/goal coding of PMC neurons?

Answer 4

Studies in freely moving monkeys show neurons fire when reaching a specific location, independent of the trajectory taken.

Question 6

What are the three main sources of input to the cerebellum?

Answer 6

Primary and secondary motor cortex, Brainstem motor nuclei, Somatosensory and vestibular feedback

Question 7

What is the main function of the cerebellum?

Answer 7

While movement is initiated, the cerebellum is responsible for a quality check of the movement.
- Cerebellum will give you an alternate plan to keep you from deviating form the target.

Question 8

What role does the cerebellum play in motor learning?

Answer 8

It helps in learning and refining movement, especially those that require precise timing.

Question 9

What happens when the cerebellum is damaged?

Answer 9

Loss of coordination, inaccurate movements, tremors, poor balance, speech and eye movement problems, and difficulty learning new motor skills.

Question 10

What was the older view of cerebellar function and what is the modern view now?

Answer 10

That it was purely for motor control (sensorimotor).

Now: It also contributes to sensory, cognitive, emotional, and memory processing.

Question 11

What theory explains the cerebellum’s role in learning?

Answer 11

The cerebellum helps learn from errors and predict future errors.

Question 12

Give an example of cerebellar function in everyday life.

Answer 12

excercise machine that changes speed in each leg.

Question 13

Why is the cerebellum considered functionally complex?

Answer 13

Because of its dense neuron count and extensive connectivity with other brain regions.

Question 14

How is the structure of the basal ganglia different from the cerebellum?

Answer 14

The basal ganglia are irregular and not organized into lobes or layers like the cerebellum.

Question 15

Do the basal ganglia send direct signals to muscles?

Answer 15

No — they influence movement indirectly through loops that connect with the cortex and cerebellum.

Question 16

What are the functions of the basal ganglia?

Answer 16

• To modulate and control motor output.
• Makes movement smoother and easier to control.

Question 17

What types of learning involve the basal ganglia?

Answer 17

Habit learning (gradual, trial-by-trial learning) and classical conditioning (learning through association).

Question 18

What are the two main roles of the basal ganglia in sensorimotor function?

Answer 18

Movement vigor — controlling the speed and force of movement.
Movement inhibition— suppressing unwanted or inappropriate movements.
(Example: resisting the urge to yawn or scratch in public.)

Question 19

What happens if the basal ganglia fail to inhibit unwanted movement?

Answer 19

It can lead to motor or psychiatric symptoms, such as tremors, tics, or compulsive behaviors.

Question 20

What neurological disorders are linked to basal ganglia dysfunction?

Answer 20

Parkinson’s disease , Huntington’s disease and tourette’s.

Question 21

What do the basal ganglia and cerebellum have in common?

Answer 21

Both modulate movement and form loops with cortical motor areas.

Question 22

What are the two main types of descending motor pathways, and what do they have in common?

Answer 22

Types:
* Dorsolateral pathways
* Ventromedial pathways

Common features:

• Each has two tracts (direct & indirect)
• Originate in the cerebral cortex
• Control voluntary movement

Question 23

How do dorsolateral and ventromedial pathways differ in their synaptic connections?

Answer 23

Dorsolateral:

• When the signals leave the spinal cord, they snapyse only n the contralateral half.
• Less diffused

Ventromedial:

• They descend through both sides of the spinal cord , bilateral
• More diffused

Question 24

What muscles do the dorsolateral and ventromedial tracts control?

Answer 24

Dorsolateral:
Controls distal muscles (hands, fingers, face, toes)

Ventromedial:
Controls proximal muscles (trunk, shoulders, hips