The basal nuclei, sometimes called the basal ganglia, include the caudate nucleus, putamen, and globus pallidus (chapter 8; see fig. 8.11). Often included in this group are other nuclei of the thalamus, subthalamus, substantia nigra, and red nucleus. Acting directly via the rubrospinal tract and indirectly via synapses in the reticular formation and thalamus, the basal nuclei have profound effects on the activity of lower motor neurons.
In particular, through their synapses in the reticular formation, the basal nuclei exert an inhibitory influence on the activity of lower motor neurons. Damage to the basal nuclei thus results in increased muscle tone, as previously described. People with such damage display akinesia, lack of desire to use the affected limb, and chorea, sudden and uncontrolled random movements (table 12.8).
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