Neuroscience Analysis of Occupational Performance (OCTH 455)
and
Neuroscience (PTRS 850)
Motor Systems Review: Question #2
The Question
Give a behavioral example, with a neurological explanation, of the release phenomenon in relation to a) the basal ganglia, b) cerebellum, and c) somatic motor system.
The Answer
Lesions of the nervous system may result in both negative signs (loss or diminished responses; e.g., reduced muscle strength) and positive signs (appearance of abnormal and stereotyped responses not observed in the intact system). Positive signs (also called release phenomena) result from the withdrawl of normal ongoing (tonic) inhibition within the neuronal circuit mediating the behavior.
A) Basal Ganglia: Sporadic and excessive movements (ballisims) associated with Huntington's disease due to failure of the subthalamus to properly modulate output messages from the globus pallidus nucleus.
B) Cerebellum: Errors in timing and sequencing of complex movements due to failure of cerebellar feed-forward mechanisms; hypotonia, ataxia, diysdiadochokinesia, and intention tremor.
C) Somatic motor system: Increased muscle tone associated with damage to these upper motor neurons; spasticity.
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