Name = Basal ganglia
Latin = nuclei basales
Caption = Basal ganglia labeled at top right.
BrainInfoType = hier
BrainInfoNumber = 206
MeshName = Basal+Ganglia
MeshNumber = A08.186.211.730.885.105
DorlandsPre = n_11
DorlandsSuf = 12580456
The basal ganglia (or basal nuclei) are a group of nuclei in the
braininterconnected with the cerebral cortex, thalamusand brainstem. Mammalian basal ganglia are associated with a variety of functions: motor control, cognition, emotions, and learning. In modern use the term 'ganglia' is in this instance considered a misnomer; 'ganglion' refers to concentrations of neural nuclei in the periphery only (for example those of the autonomic nervous system), and the term 'basal nuclei' is preferred.
The acceptance that the basal ganglia system constitutes one major cerebral system has been slow to appear.
The first anatomical identification of distinct subcortical structures was published by
Thomas Willisin 1664. [Andrew Gilies, " [http://www.anc.ed.ac.uk/~anaru/research/history/ A brief history of the basal ganglia] ", retrieved on 27 June 2005] For many years, the term corpus striatum was used to describe a large group of subcortical elements, some of which were later discovered to be functionally unrelated. Additionally, the putamenand the caudate nucleuswere not linked together. The putamen was thought to be associated to the pallidumin what used to be called the "nucleus lenticularis" (see lentiform nucleuson the fig.).
Pioneering work by Cécile and Oskar Vogt (1941) greatly simplified the description of the basal ganglia by proposing the term
striatumto describe the group of structures consisting of the caudate nucleus, the putamen and the mass linking them ventrally, the nucleus accumbens.
The striatum gets its name from the striated appearance created by radiating dense bundles of striato-pallido-nigral
axons, described by anatomist Kinnear Wilson as "pencil-like". The anatomical link of the striatum with its primary targets, the pallidumand the substantia nigrawas later discovered. Together, these structures constitute the striato-pallido-nigral bundle, which is the core of the basal ganglia. This nerve bundle forms the so-called "comb bundle of Edinger" when it crosses the internal capsule.
Additional structures that later became associated with the basal ganglia are the "body of Luys" (1865) (nucleus of Luys on the figure) or
subthalamic nucleus, whose lesion was known to produce movement disorders. More recently, other areas such as the central complex(centre médian-parafascicular) and the pedunculopontine complexhave been thought to be regulators of the basal ganglia.
At the beginning of the 20th century, the basal ganglia system was associated with motor functions, as lesions of these areas would often result in disordered movement in humans (
chorea, athetosis, Parkinson's disease).
The five individual nuclei that make up the
primatebasal ganglia, along with their major subdivisions, are:
striatum, which consists of
* external segment of the
* internal segment of the globus pallidus (GPi)
** substantia nigra pars compacta (SNc)
** substantia nigra pars reticulata (SNr)
** substantia nigra pars lateralis (SNl)
There are 2 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). Images show two schematic coronal cross-sections of the
humanbrain with nuclei of the basal ganglia labeled on the right side.
Functionally, the basal ganglia consist of a series of circuits, such as skeletomotor, limbic and occulomotor circuits. Each circuit projects to specific nuclei within the basal ganglia and its projections e.g. the skeletomotor circuit projects to the ventral lateral, lateral ventral anterior and centromedian thalamic nuclei.
Comparative anatomy and naming
"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
amniotes (mammals, birds, and reptiles) and amphibians. The anatomical connections of these nuclei and their pharmacologyalso appear relatively conserved. Non- tetrapodvertebrates 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
* The "striatum" and "external segment of the globus pallidus" in primates are called the "paleostriatum augmentatum" and "paleostriatum primitivum" respectively in birds.
A clear emergent issue in comparative anatomy of the basal ganglia is the development of this system through phylogeny as a convergent cortically re-entrant loop in conjunction with the development and expansion of the cortical mantle. There is controversy, however, regarding the extent to which convergent selective processing occurs versus segregated parallel processing within re-entrant closed loops of the basal ganglia. Regardless, the transformation of the basal ganglia into a cortically re-entrant system in mammalian evolution occurs through a re-direction of pallidal (or "paleostriatum primitivum") output from midbrain targets such as the superior colliculus, as occurs in
sauropsidbrain, to specific regions of the ventral thalamus and from there back to specified regions of the cerebral cortex that form a subset of those cortical regions projecting into the striatum. The abrupt rostral re-direction of the pathway from the internal segment of the globus pallidus into the ventral thalamus--via the path of the ansa lenticularis--could be viewed as a footprint of this evolutionary transformation of basal ganglia outflow and targeted influence. The evolutionary emergence of cortical re-entrant systems in the brain has been postulated by Gerald Edelmanas a critical basis for the emergence of primary consciousnessin the theory of Neural Darwinism.Fact|date=May 2007
Basal ganglia connectivity is illustrated in the figure.
The striatum is the main (but not the only) input zone for other brain areas to connect to the basal ganglia. Via the striatum, the basal ganglia receives input from the cortex, mainly from the motor and prefrontal cortices.
The circuitry of the basal ganglia is often divided into two major pathways, the "direct pathway" and the "indirect pathway":
Dopaminefrom the substantia nigrapars compacta stimulates all of the dopamine receptors, but because the different pathways express different receptors, and the different receptors have different effects, dopamine serves to activate the direct pathway over the indirect pathway, and thus increase the signal to the thalamus.
The different types of neuron of the basal ganglia biosynthesize different
Other disorders linked with the basal ganglia
Attention-deficit hyperactivity disorder(ADHD)
Athymhormic syndrome( PAP syndrome)
Cerebral palsy: basal ganglia damage during second and third trimester of pregnancy
Foreign accent syndrome(FAS)
* Tourette's disorder
Tardive dyskinesia, caused by chronic antipsychotictreatment
Stuttering[cite journal |author=Alm PA |title=Stuttering and the basal ganglia circuits: a critical review of possible relations |journal=Journal of communication disorders |volume=37 |issue=4 |pages=325–69 |year=2004 |pmid=15159193 |url=http://theses.lub.lu.se/scripta-archive/2005/02/02/med_1035/part2/Per_Alm_Paper_II.pdf |doi=10.1016/j.jcomdis.2004.03.001]
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". [cite book|last=Soltanzadeh|first=Akbar|title= Neurologic Disorers|isbn=ISBN 964-6088-03-1|publisher=Jafari|year=2004|location=Tehran]
Anatomical subdivisions and connections of the basal ganglia
Nathaniel A. Buchwald
Primate basal ganglia system
* Nolte, John, "The Human Brain: An Introduction to its Functional Anatomy" (Fifth Edition). (St. Louis: Mosby, Inc., 2002), 464-484. ISBN 0-323-01320-1
* Parent, André, "Comparative Neurobiology of the Basal Ganglia" (Wiley, New York, 1986), ISBN 0-471-80348-0
* [http://rad.usuhs.edu/medpix/medpix.html?mode=image_finder&action=search&srchstr=basal%20ganglia&srch_type=all Imaging of Basal Ganglia] at USUHS
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