Basal ganglia and cerebellum

Question 1

What are the functions of the motor cortex?

Answer 1

Initiation of voluntary movement

Skilled, dextrous movements

Integration of movement with maintenance of postural stability and the physical envrionment

Question 2

Where is the motor cortex located?

Answer 2

Immediately rostral/anterior to the central sulcus

Question 3

Describe the mapping of the primary motor cortex?

Answer 3

Simple mapping in comaprison to other motor areas

Topographic arrangement

Motor homunculus

Contralteral actions with stimulation

Question 4

Which areas of the brain are active in more complex motor movements?

Answer 4

In addition to primary motor area, areas outside of it are stimulated with more complex movements

eg. SMA and primary sensory cortex

Question 5

Describe the suggested functions of the motor association areas?

Answer 5

Planning of movements

Performance of more complicated programs or sequences of movements

Question 6

What is really represented by the motor cortex?

Answer 6

The types of movements that we actually need to perform

eg. bringing hand to chest to examine something or hand to face to eat something

Question 7

How do cortical motor neurons differ from spinal motor neurons?

Answer 7

In cortex, neurons have different functional allocations

Neurons for particular types of tasks

Not like spinal cord, where neuron must be active if muscle is active

Question 8

Describe the concept of mirror neurons?

Answer 8

Neurons respond to seeing a movement performed, as well as performing that movement ourselves

Preparatory, as well as a way of encoding the means by which a goal would be achieved

Important for motor learning

Question 9

Describe the inputs to the motor areas?

Answer 9

Primary motor cortex: inputs from association areas and somatosensory cortex, particularly other parts of parietal cortex that synthesise higher order representations of our environment

Premotor areas: from high level representation of environment, as well as prefrontal areas, which suggests that prefrontal areas are telling us about the value/salience/meaning of things

Question 10

Describe how motor pathways relate to visual pathways in the brain?

Answer 10

Dorsal pathway = where = reaching

Ventral pathway = what = grasping

Two motor pathways that feed into different areas of the motor cortex and association areas, and integrate behaviour about an object that we see to perform a goal

Question 11

Describe the three main functions of the basal gangli?

Answer 11

1) Selection of complex patterns of voluntary movements
2) Evaluating the success of actions in achieving the goals of those actions
3) Initiating movements

Question 12

Describe the basic anatomy of the basal ganglia?

Answer 12

Made up of five nuclei

3 in midbrain: caudate, putamen, globus pallidus

1 in diencephalon: subthalamic nucleus

1 in midbrain: substantia nigra

Question 13

How are the basal ganglia affected in Parkinson’s disease?

Answer 13

Loss of dopaminergic neurons in substantia nigra > inability to initiate movement

Question 14

How are the basal ganglia affected in Huntington’s disease?

Answer 14

Caudate and putamen reduced, almost lost

Question 15

Describe the general principles of the pathways through the basal ganglia?

Answer 15

Two pathways by which the motor cortex connects back with itself

Direct pathway: selects patterns of motor activity

Indirect pathway: suppresses other movements, especially similar ones

Dopamine is critical

Question 16

Describe the functions of the cerebellum?

Answer 16

Coordinating timing and sequence of movements

Maintenance of muscle tone

Motor learning

Planning sequences of muscle activation for complex movements

Question 17

Which parts of the brain does the cerebellum interact with?

Answer 17

Motor cortex

Brainstem

Question 18

Briefly describe the anatomy of the cerebellum?

Answer 18

Tightly folded

Three main lobes with three connections to brainstem (superior, middle and inferior peduncles)

Every part the same in terms of cellular structure

Question 19

Describe the functional organisation of the cerebellum?

Answer 19

Medial to lateral

Question 20

What is the major consequence of cerebellar lesions?

Answer 20

Ataxic movements

Inability to follow path/route

Effects are ipsilateral for a unilateral lesion

Question 21

Describe the signs of anterior lobe syndrome of the cerebellum?

Answer 21

Ataxic gait

Loss of inter-limb coordination

Question 22

What is a major cause of anterior lobe syndrome in the cerebellum?

Answer 22

Chronic ethanol toxicity

Question 23

Describe the signs of posterior lobe syndrome of the cerebellum?

Answer 23

Dysmetria (overshoot in precision reach)

Dysdiadochokinesia (inability to rapidly alternate movements)

Speech abnormality

Question 24

What is flocculonodular syndrome?

Which lobe of the cerebellum is it associated with?

Answer 24

Truncal ataxia (inability to stabilise trunk)

Associated with posterior lobe

Question 25

On which side of the body do unilateral cerebellar lesions present?

Why?

Answer 25

Cerebellar lesions present ipsilaterally

Due to double cross

Output from cerebellum crosses over and projects to motor thalamus or brainstem and to cortex in crossed pathway

Damage to cerebellum > affects contralateral part of cerebrum > affects ipsilateral side of body

Question 26

Describe the role of the cerebellum in learning and adaptation?

Answer 26

Cerebellum is required to make adaptations to motor programs