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Basal nuclei- basic facts Terminology Corpus striatum=lentiform and caudate nuclei Lentiform nucleus=putamen and globus pallidus Striatum= putamen and globus pallidus Pallidum=globus pallidus Anatomically consist of gray matter associated with lateral ventrivle Composed of striatum [caudate nucleus, nucleus accumbens, putamen] and the globus pallidus, which is composed of external and internal divisions Clinically and physiologically, ‘basal nuclei’ include corpus striatum, subthalamic nucleus and substantia nigra The best understood functions of basal nuclei are in the production of movements, but extensive connections with the temporal and frontal lobes indicate involvement in memory, emotion, and other cognitive functions The striatum, subthalamic nucleus and subthalamic nucleus and substantia nigra receive excitatory afferents from cerebral cortex. Dopaminergic neurons in substantia nigra and ventral tegmental area excite some striatal neurons and inhibit others The major output of the striatum is to the pallidum, and it is inhibitory. Excitatory input to the pallidum comes from the subthalamic nucleus The output of the pallidum, which is also inhibitory, is to various thalamic nuclei. The thalamic nuclei project to and excite the premotor and supplementaty motor areas of the cerebral cortex, cortical areas concerned with eye movements, and parts of the prefrontal and temporal cortex Other pallidal efferents inhibit the subthalamic nucleus, superior colliculus, and pedunculopontine nucleus The pedunculopontine nucleus, which is located in the reticular formation, has extensive projections that influence descending motor pathways, the waking state and [by way of the basal cholinergic forebrain nuclei] neuronal activity throughout the cerebral cortex At rest, neurons in the striatum are quiescent and those in the pallidum are active, thereby inhibiting the thalamic excitation of the motor cortex. Before and during a movement, the striatum becomes active and inhibits the pallidum, allowing more excitation of motor thalamic nuclei and cortex The corpus striatum may normally be the site in which instructions for parts of learned movements are remembered and from which they are transmitted to the motor cortex for assembly and eventual execution by corticospinal pathways to the motor neurons. Comparable circuitry exists for the control of movements of the eyes The nucleus accumbens and most of the ventral parts of the pallidum are active in behavioral responses to a wide variety of rewarding or pleasurable stimuli Conditioned reflexes passing through these nuclei and their associated cortical areas have been implicated in drug addiction The basal cholinergic nuclei of the forebrain are ventral to the corpus striatum within the anterior perforated substance. Their axons are distributed to the whole cerebral cortex, afferents to the basal nuclei are from the amygdaloid nucleus, the pallidum, and the reticular formation of the brainstem. Subcortical cholinergic neurons degenerate in patients with Alzheimer’s disease and some other forms of dementia