Topic 8

Question 1

What are central and peripheral constraints?

Answer 1

Central constraints: on movement comes from the organization of the brain and nervous system.

Peripheral constraints: come from the physical structure of the body

Question 2

Name and describe the five constraints on somatotopic organization that were presented

Answer 2

1. Convergent: output from a large M1 territory controls a particular body joint or muscle
2. Divergent: output of many single M1 (primary motor neuron) neurons reaches multiple spinal MN ( motor neuron) pools
3. Horizontal Connections: interlink the cortex throughout a major body part region
4. Partial inactivation: of major region affects many smaller body parts simultaneously
5. Plasticity: limits the extent to which a specific body part can be assigned to a specific part of the cortex

Question 3

Explain the cortical piano metaphor for cortical arrangement and how it explains the production of complex voluntary movement.

Answer 3

The cortical piano metaphor describes how different areas of the motor cortex control different parts of the body, just like keys on a piano produce different notes. This arrangement, with its overlapping and interconnected regions, allows for the production of complex movements by activating different combinations of cortical areas.

Question 4

Explain an example of peripheral constraints and how would it influence a specific movement.

Answer 4

Juncturae Tendinium connects the EDC tendons in the fingers. These connections limit independent finger extension. when you try to extend one finger, the juncturae tendinium will also cause some extension in the adjacent fingers.

Question 5

Describe what is needed to plan a reaching movement.

Answer 5

Planning a reaching movement involves the central nervous system considering the limb’s current state (position, velocity, and acceleration) and the target’s location. the CNS plans straight movements visually. the movement proceeds using a “next state planner:” which utilizes feedback on the limb’s state and the target’s estimated location to determine next step.

Question 6

what happens if the movement is interrupted?

Answer 6

The CNS must adjust the planned trajectory based on the new information about the limb’s position and the target.

Question 7

Explain the prism adaptation study. What do studies on prism adaptation tell us about planning reaches and upper limb control?

Answer 7

in the prism adaptation studies, subjects were prisms that changed their visual field. Initially, reaching movements are inaccurate because of the visual distortion. However, the practice, with practice, they adapt and learn to reach accurately despite the prisms. This adaptation suggests that the brain uses visual feedback to update its internal model of the relationship between motor commands and resulting hand position. This highlights th role of sensory feedback in motor planning and the brain’s ability to adapt to changes in sensory input to maintain accurate movements.