The are a group of
Nuclei in the
Brain associated with motor and
Learning functions. However, no single function can be definitively assigned to the
Mammalian basal ganglia.
The first
Anatomical identification of distinct subcortical structures was published by the
English anatomist
Thomas Willis in
1664 . At that time, it was referred to as the corpus striatum (comprising only the
Globus Pallidus segments and
Striatum ). At the beginning of the 20th century, it was associated with motor functions, as lesions of these areas would often result in disordered movement in humans. In
1925 ,
Kinnear Wilson described them as the "dark basement of the brain."
The five individual nuclei that make up the
Primate basal ganglia, along with their major subdivisions, are:
Images show two schematic
Coronal cross-sections of the
Human brain with nuclei of the basal ganglia labeled on the right side.
As it refers to a group of nuclei, the term "basal ganglia" is plural (the singular of ganglia is ''
Ganglion ''). However this is a
Misnomer , as “ganglion” refers to a
Somatic cluster within the
Peripheral Nervous System , whereas the basal ganglia are within the
Central Nervous System (CNS). A somatic cluster within the CNS is referred to as a nucleus, so some
Neuroanatomists refer to the basal ganglia as the “basal nuclei”.
There are two sets of basal ganglia in the mammalian brain, mirrored in the left and right hemispheres. Two coronal sections are used to show the basal ganglia; the STN and substantia nigra lie deeper back in the brain (more
Caudal ).
"Basal ganglia"-like areas are found in the central nervous systems of many species. The striatal and pallidal components can be clearly identified in all
Amniote s (mammals, birds, and reptiles) and
Amphibian s. The anatomical connections of these nuclei and their
Pharmacology also appear relatively conserved. Non-
Tetrapod vertebrates such as fish also display basal ganglia-like structures, although the data are less clear in this case.
The names given to the various nuclei of the basal ganglia are different in different species. For example, the "internal segment of the globus pallidus" in primates is called the "entopenduncular nucleus" in
Rodent s. The "striatum" and "external segment of the globus pallidus" in primates are called the "paleostriatum augmentatum" and "paleostriatum primitivum" respectively in birds.
Neurons of the various basal ganglia nuclei use a variety of
Neurotransmitter s. The most widely used is the inhibitory transmitter
GABA (connections using GABA are shown in blue in the diagram below). Of particular interest is the neurotransmitter of the pigmented
Substantia Nigra ''pars compacta'' neurons, called
Dopamine . Disruption in the production or transmission of dopamine can lead to serious motor and cognitive deficits (for example, see
Parkinson's Disease ). The substantia nigra pars compacta (SNc) primarily targets the striatum with this neurotransmitter (shown as the magenta connection in the classic connectivity diagram below), and it is thought to play an important role in learning (see
LTP /
LTD ).
