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The pars compacta (SNpc) is one of two subdivisions of the substantia nigra of the midbrain (the other being the pars reticulata); it is situated medial to the pars reticulata. It is formed by dopaminergic neurons. [1] It projects to the striatum and portions of the cerebral cortex. [2] It is functionally involved in fine motor control.
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] Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. [2]
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.
The nigrostriatal pathway transmits dopaminergic neurons from the zona compacta of the substantia nigra [8] to the caudate nucleus and putamen. The substantia nigra is located in the midbrain, while both the caudate nucleus and putamen are located in the dorsal striatum. motor function; reward-related cognition; associative learning; addiction ...
Substantia nigra. Pars compacta; Pars reticulata; Interpeduncular nucleus; Cerebral peduncle. Crus cerebri; Mesencephalic cranial nerve nuclei. Oculomotor nucleus (III) Edinger-Westphal nucleus; Trochlear nucleus (IV) Mesencephalic duct (cerebral aqueduct, aqueduct of Sylvius)
The pedunculopontine nucleus lies below the red nucleus, caudal to the substantia nigra and adjacent to the superior cerebellar peduncle.It has two divisions of subnuclei; the pars compacta, containing mainly cholinergic neurons, and the pars dissipata, containing mainly glutamatergic neurons and some non-cholinergic neurons.
Oscillatory and synchronous activity [14] [15] is likely to be a typical pattern of discharge in subthalamic neurons recorded from patients and animal models characterized by the loss of dopaminergic cells in the substantia nigra pars compacta, which is the principal pathology that underlies Parkinson's disease.
Group A9 is the most densely packed group of dopaminergic cells, and is located in the ventrolateral midbrain of rodents [6] and primates. [4] It is for the most part identical with the pars compacta of the substantia nigra as seen from the accumulation of neuromelanin pigment in the midbrain of healthy, adult humans.