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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