MOTOR SYSTEMS

I. The Cortex and Motor Function

A. Electrical stimulation of motor cortex reveals its somatotopic organization.

1. However, primary motor cortex is not directly connected to muscles.

B. Entire cortex is involved in the planning of complex actions.

1. Posterior parietal cortex provides information about current body position.

2. Parallel waves of activity sweep across different parietal®frontal regions.

C. Dorsolateral Prefrontal, Premotor, Supplementary Motor Cortex

II. Parkinson’s Disease: progressive loss of dopamine-producing neurons

A. Behavioral symptoms:

B. Diseased brain regions: substantia nigra and amygdala

1. Substantia nigra: “headquarters” or source of nigrostriatal pathway

2. Pathway provides input to basal ganglia

C. Normal role of basal ganglia is to organize/refine movement.

1. Movements are “refined” by inhibiting inappropriate options, synchronizing the output of cortex

2. Efferent connections: loop back to cortex and also out through spinal cord

3. Nigrostriatal destruction ® excessive inhibition of other motor regions

D. Possible causes:

1. genetic predispositions

2. drug and/or environmental toxicant exposure

E. Pharmacological treatments:

1. L-dopa

2. MAO inhibitors

3. individualized combination of the above

4. Neurosurgery

a. Deep brain stimulation of the subthalamic nucleus vs. lesions of the internal globus pallidus

b. Stem cell therapy vs. fetal tissue transplants