IC3 Motor Behaviour

Question 1

What are the 3 types of movements generated?

Answer 1

1. Reflexes - involuntary
2. Rhythmic motor patterns - voluntary initiation and termination (e.g., walking)
3. Voluntary

Question 2

Hierarchical features of motor control

Answer 2

1. Cortex (primary motor cortex, premotor area) - voluntary movement
2. Brain stem - postural reflexes, rhythmic motor patterns

• Rhythmic motor patterns usually triggered by the cortex (somewhat voluntary)

3. Spinal cord - motor neurons, control muscle activity

• Efferents are the final common pathway, they control the muscles for all types of motor behavior
• Spinal efferents found mostly in ventral horn

Question 3

Where is the primary motor cortex and the premotor cortex?

Answer 3

Primary motor cortex is the precentral gyrus, in front of the central sulcus

*The primary function of the motor cortex is to generate signals to direct the movement of the body

Premotor cortex is in the somatic motor association area in front of the primary motor cortex

Question 4

Loss of output in the final common pathway (spinal cord efferents => control muscle activity), may lead to?

Answer 4

Flaccid paralysis - muscles unable to contract, no muscle activity

Question 5

Cerebellum function

Answer 5

Main function: coordination
May also play a role in: muscle tone, balance

• Cerebellum interacts with cortex and brainstem, and indirectly affects movement by adjusting the output of the efferent => therefore indirectly modulates the effects in the spinal cord to coordinate limb movement

Question 6

Lesions to the cerebellum will result in…

Answer 6

• Disruption of coordination of limb and eye movement
• Impaired balance
• Decrease in muscle tone

Question 7

How would right side hemispheric lesion (affecting cerebellum) affect walking?

Answer 7

Deviation towards the right while walking (stagger and deviate to the involved side)

Cerebellar ataxia

Question 8

Basal ganglia interacts with ____

Answer 8

Basal ganglia interacts with the cortex

Basal ganglia is located in the temporal lobe

Question 9

Basal ganglia function

Answer 9

Control your body’s voluntary movements, motor control. They can approve or reject movement signals that your brain sends, filtering out unnecessary or incorrect signals.

Question 10

Basal ganglia input regions:

Answer 10

• Caudate
• Putamen

ICP

Question 11

Basal ganglia output regions:

Importance of output regions

Answer 11

• Global pallidus
• Subthalamic nucleus
• Substantia nigra

OGSS

Output region is important for appropriate initiation and selection of motor program

Question 12

Damage to basal ganglia causes:

Answer 12

Disorder of movement

• tremor
• rapid flicking movements or chorea (jerking)
• violent flailing movement or ballism (violent flinging)
• slow writhing/twisting movements (athetosis, dystonia - muscle contract involuntarily)
• bradykinesia (slow movement)

Disorder of posture

• rigidity

Question 13

Give an example of basal ganglia disorder - linked to dopamine neurotransmitter (present in high concentrations in basal ganglia)

Answer 13

Degeneration of dopamine neurons in basal ganglia leads to Parkinson’s disease (dopamine deficit)

*Marked by: tremor, rigidity, bradykinesia

Question 14

How might basal ganglia disorder (Parkinson’s) be treated?

Answer 14

Manipulate the basal ganglia by:

• Electrodes to control tremors (alter signal with passage of current)
• L-dopa (precursor of dopamine)
• Dopamine mimetics

Question 15

Describe the descending control of efferent

Answer 15

Involve corticospinal (from cortex to spinal cord) and brainstem (from brainstem to spinal cord) pathway:

Cortex and brainstem influence the efferent for execution of behaviours

This occurs through long descending axons from site of origin (e.g., neurons in cortex) to the efferents in the spinal cord

Axon will pass through basal ganglia and cerebellum that feed signal into cortex and/or brainstem to control the efferents

Question 16

Summary of how the brain influences voluntary behavior

Answer 16

1. Posterior parietal cortex

• gathers information from somatosensory + proprioceptive + visual cortex to build an idea of our relative position in space

2. Anterior frontal lobe (prefrontal cortex)

• Decision making

3. Premotor cortical areas

• Involved in planning and organizing movements and actions

4. Primary motor cortex

• Signal from primary motor cortex sent to brainstem and efferent (descending control of efferent)