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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 globus pallidus (GP), also known as paleostriatum or dorsal pallidum, [1] is a major component of the subcortical basal ganglia in the brain.It consists of two adjacent segments, one external (or lateral), known in rodents simply as the globus pallidus, and one internal (or medial).
The basal ganglia functions to tonically inhibit movement, mainly in the absence of motor cortex command, via GABAergic inhibition of the ventral lateral nucleus and ventral anterior nucleus of the thalamus, as well as the superior colliculus and mesopontine tegmentum of the brain stem.
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.
As the GPi is one of the direct output centers of the basal ganglia, this causes disinhibition of the thalamus, increasing overall ease of initiating and maintaining movement. As this pathway only contains one synapse (from the striatum to the internal globus pallidus), it is known as the direct pathway .
The cerebrum (pl.: cerebra), telencephalon or endbrain [1] is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system.
Situated ventral to the pallium in the basic vertebrate forebrain plan (though representing a topologically rostral field in neural plate fate maps) is another region of telencephalic gray matter known as the subpallium, which is the progenitor area for the basal ganglia, a set of structures that play a crucial role in the executive control of ...
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.