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The putamen (/ p j u ˈ t eɪ m ə n /; from Latin, meaning "nutshell") is a subcortical nucleus with a rounded structure, in the basal ganglia nuclear group. It is located at the base of the forebrain and above the midbrain. The putamen and caudate nucleus together form the dorsal striatum.
In the direct pathway, the motor cortices send activating signals to the caudate and putamen (which together form the dorsal striatum). The cells of the direct pathway in the caudate and putamen that receive these signals are inhibitory and, once they become activated, send inhibitory signals to the GPi and SNpr and stop activity there.
The substantia nigra is located in the ventral midbrain of each hemisphere. It has two distinct parts, the pars compacta (SNc) and the pars reticulata (SNr). The pars compacta contains dopaminergic neurons from the A9 cell group that forms the nigrostriatal pathway that, by supplying dopamine to the striatum, relays information to the basal ganglia.
Anatomical overview of the main circuits of the basal ganglia. Subthalamic nucleus is shown in red. Picture shows 2 coronal slices that have been superimposed to include the involved basal ganglia structures. + and - signs at the point of the arrows indicate respectively whether the pathway is excitatory or inhibitory in effect.
The basal ganglia (BG) or basal nuclei are a group of subcortical nuclei found in the brains of vertebrates. In humans and other primates , differences exist, primarily in the division of the globus pallidus into external and internal regions, and in the division of the striatum .
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. [1]
The indirect pathway, sometimes known as the indirect pathway of movement, is a neuronal circuit through the basal ganglia and several associated nuclei within the central nervous system (CNS) which helps to prevent unwanted muscle contractions from competing with voluntary movements. [1] It operates in conjunction with the direct pathway.
The external capsule is a route for cholinergic fibers from the basal forebrain to the cerebral cortex. The putamen separates the external capsule from the internal capsule medially and the claustrum separates it from the extreme capsule laterally. But the external capsule eventually joins the internal capsule around the lentiform nucleus.