The document discusses several topics related to brain mechanisms of movement: 1) The primary motor cortex and areas near it such as the premotor cortex and supplementary motor cortex are involved in controlling movement, with the primary motor cortex sending axons to the basal ganglia and brainstem/spinal cord. 2) The cerebellum plays an important role in motor control and learned motor behaviors through connections with other parts of the brain and spinal cord. 3) Basal ganglia structures like the caudate nucleus, putamen, and globus pallidus are important for habit learning and movement selection, and disorders like Parkinson's and Huntington's disease impact these areas.

1. Brain Mechanisms of Movement

2. Role of the Cerebral Cortex Primary Motor Cortex Precentral gyrus of the frontal cortex stimulation elicits movements Axons from Primary Motor Cortex go to basal ganglia while other motor axons go to the brainstem & spinal cord Cerebral Cortex & Complex Actions Stimulation of motor cortex elicits complex movement patterns The motor cortex is stimulated when movement is imagined

3. Areas Near the Primary Motor Cortex Posterior Parietal Cortex Primary Somatosensory Cortex Prefrontal Cortex Premotor Cortex Supplementary Motor Cortex

4. Connections from the Brain & Spinal Cord Dorsolateral Tract Axons from the primary motor cortex & red nucleus synapse in the spinal cord Pyramids in medulla contain dorsolateral tract crossing that contralaterally controls movements of the fingers, toes, hands, etc.

5. Connections from the Brain & Spinal Cord Ventromedial Tract Contains axons from the primary motor cortex, supplementary motor cortex, midbrain tectum, reticular formation & the vestibular nucleus Axons from the ventromedial tract go to both sides of the spinal cord & are largely responsible for neck, shoulder, & trunk movements

6. The Role of the Cerebellum Involved in Motor Control & Learned Motor Behavior Linked to Habit Formation, Aspects of Attention, Timing, & Other Psychological Motor Functions

7. The Cerebellum Cellular Organization Receives input from the spinal cord, from each sensory system via the cranial nerve nuclei, & cerebral cortex where it eventually reaches the cerebellar cortex Neurons in the cerebellar cortex are: 1. Arranged in precise geometrical patterns with multiple repetitions of the same unit 2. Action potentials of parallel fibers excite one Purkinje cell after another 3. Purkinje cells inhibit cells of the nuclei of the cerebellum & the vestibular nuclei in the brain stem 4. Output of Purkinje cells control the timing of movements including turning on & off

8. Basal Ganglia Includes: Caudate Nucleus, Putamen, & Globus Pallidus Caudate nucleus & Putamen are input, globus pallidus is output Important for Habit Learning & the Selection of Movement Obsessive-compulsive disorder is linked to increased activity in the caudate nucleus & prefrontal cortex

9. Parkinson’s Disease Symptoms Rigidity, resting tremor, slow movements & difficulty initiating physical & mental activity, cognitive defects in memory & reasoning 1 in 100 with onset after age 50 Immediate cause: gradual progressive death of neurons in Substantia Nigra Possible causes: Genetics; MPTP, a chemical that the body converts into MPP (a toxin destroys dopamine neurons; probably a mixture of causes

10. Parkinson’s Disease Standard Treatment L-Dopa Precursor to dopamine Effectiveness varies Doesn’t prevent the loss of dopamine containing neurons & may contribute to the death of neurons Produces harmful side-effects Alternative Treatments Antioxidant drugs Direct dopamine agonists Glutamate antagonists Neurotrophins Apoptosis blockers High frequency electrical stimulation of the Globus Pallidus Surgical damage to the Globus Pallidus or parts of the Thalamus

11. Huntington’s Disease Severe Degenerative Neurological Disorder Symptoms: twitches, tremors, & writing movements; depression, memory deficits, anxiety, hallucinations, delusions, poor judgment, alcoholism, drug abuse, & sexual disorders Affects 1 in 1000 Gradual, extensive brain damage especially in the Caudate Nucleus, Putamen, & Globus Pallidus

12. Huntington’s Disease Onset Most often appears between 30 & 50 years The earlier the onset, the faster the deterioration Heredity Caused by an autosomal dominant gene on chromosome 4 Abnormal form of huntingtin , a protein found in neurons that interferes with several metabolic pathways