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20-September-2008 10:21:21 - Basal ganglia Brain: Basal ganglia Basal ganglia labeled at top right. Latin nuclei basales NeuroNames hier-206 MeSH Basal+Ganglia Dorlands/Elsevier n_11/12580456 The basal ganglia or basal nuclei are a group of nuclei in the brain interconnected with the cerebral cortex, thalamus and 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. Contents 1 History 2 Anatomical subdivisions 3 Comparative anatomy and naming 4 Connections 5 Neurotransmitters 6 Other disorders linked with the basal ganglia 7 Terminology 8 See also 9 References 10 Additional images 11 External links History 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 Willis in 1664.1 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 putamen and the caudate nucleus were not linked together. The putamen was thought to be associated to the pallidum in what used to be called the nucleus lenticularis see lentiform nucleus on the fig.. Pioneering work by Cécile and Oskar Vogt 1941 greatly simplified the description of the basal ganglia by proposing the term striatum to 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 pallidum and the substantia nigra was 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 complex have 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. Anatomical subdivisions Coronal slices of human brain showing the basal ganglia.ROSTRAL: striatum, globus pallidus GPe and GPiCAUDAL: subthalamic nucleus STN, substantia nigra SN Coronal slices of human brain showing the basal ganglia. ROSTRAL: striatum, globus pallidus GPe and GPi CAUDAL: subthalamic nucleus STN, substantia nigra SN Main article: Anatomical subdivisions and connections of the basal ganglia The five individual nuclei that make up the primate basal ganglia, along with their major subdivisions, are: rostral the striatum, which consists of putamen caudate nucleus external segment of the globus pallidus GPe internal segment of the globus pallidus GPi caudal subthalamic nucleus STN substantia nigra SN 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 human brain 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 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 rodents. 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 sauropsid brain, 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 Edelman as a critical basis for the emergence of primary consciousness in the theory of Neural Darwinism.citation needed Connections Connectivity Diagram showing glutamatergic pathways as red, dopaminergic as magenta and GABA pathways as blue. Connectivity Diagram showing glutamatergic pathways as red, dopaminergic as magenta and GABA pathways as blue. 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: Pathway Path # inhibitory pathways - Description Dopamine receptors Direct stimulatory striatum- →GPi/SNr- →thalamus+ →cortex 2 even Cortical activity that excites cells in the striatum that participate in the direct pathway leads to inhibition of areas of the GPi and SNr, which in turn removes their tonic inhibition from the thalamus. This removal of inhibition by inhibition is called disinhibition. D1 Indirect inhibitory striatum- →GPe - →STN + →GPi/SNr- →thalamus+ →cortex 3 odd In contrast, cortical activity that excites the striatal cells in the indirect pathway is thought to inhibit the thalamus by inhibiting the disinhibition. D2 Dopamine from the substantia nigra pars 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. Neurotransmitters The different types of neuron of the basal ganglia biosynthesize different neurotransmitters. Structure Neurotransmitter Description Disorders Striatum/neostriatum GABA Medium neurons, the principal cells, are inhibitory Huntington's disease Substantia nigra dopamine The substantia nigra pars compacta SNc primarily targets the striatum with this neurotransmitter shown as the magenta connection in the classic connectivity diagram above. Disruption in the biosynthesis or transmission of dopamine can lead to serious motor and cognitive deficits, such as occurs in Parkinson's disease. Globus pallidus GABA The globus pallidus contains an internal segment and an external segment. The internal segment projects to the thalamus, whereas the external segment projects to the subthalamic nucleus. Tourette's syndrome Subthalamic nucleus glutamate The neurons of the subthalmic nucleus excite neurons of the internal globus pallidus. Damage to the subthalmic nucleus may result in hemiballismus. 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 Dystonia Fahr's disease Foreign accent syndrome FAS Huntington's disease Lesch-Nyhan syndrome Obsessive-compulsive disorder Parkinson's disease Tourette's disorder Tardive dyskinesia, caused by chronic antipsychotic treatment Stuttering2 Spasmodic dysphonia Wilson's disease Terminology 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.3 See also Anatomical subdivisions and connections of the basal ganglia Nathaniel A. Buchwald Primate basal ganglia system References This needs additional citations for verification. September 2007 ^ Andrew Gilies, A brief history of the basal ganglia, retrieved on 27 June 2005 ^ Alm PA 2004. Stuttering and the basal ganglia circuits: a critical review of possible relations. Journal of communication disorders 37 4: 325-69. doi:10.1016/j.jcomdis.2004.03.001. PMID 15159193. ^ Soltanzadeh, Akbar 2004. Neurologic Disorers. Tehran: Jafari. ISBN ISBN 964-6088-03-1. Nolte, John, The Human Brain: An Introduction to its Functional Anatomy Fifth ion. 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 Reynolds JN, Hyland BI, Wickens JR 2001. A cellular mechanism of reward-related learning. Nature 413 6851: 67-70. doi:10.1038/35092560. PMID 11544526. Additional images Basal ganglia The major components of the basal ganglia are the caudate nucleus, putamen, and globus pallidus Schematic representation of the chief ganglionic categories I to V. External links Basal+ganglia at eMedicine Dictionary Imaging of Basal Ganglia at USUHS v d e Brain - Basal ganglia Rostral, telencephalon corpus striatum striatum: Putamen - Caudate nucleus lentiform nucleus: Putamen - Globus pallidus GPe, GPi Caudal, diencephalon Subthalamic nucleus Caudal, mesencephalon Substantia nigra Pars compacta, Pars reticulata Paths direct: Motor cortex → Striatum → GPi → Subthalamic fasciculus → Thalamus → Motor cortex indirect: Motor cortex → Striatum → GPe → Subthalamic nucleus → GPi → Subthalamic fasciculus → Thalamus → Motor cortex nigrostriatal pathway: Pars compacta → Striatum note: nucleus accumbens, claustrum and amygdala are considered part of basal ganglia by some sources Retrieved from http://en..org/wiki/Basal_ganglia Categories: Central nervous system | Cerebrum | NeuroanatomyHidden categories: All articles with statements | Articles with statements since May 2007 | Articles needing additional references from September 2007 Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages БългарÑ?ки Català Česky Dansk Deutsch Ελληνικά Español Français עברית Magyar Nederlands 日本語 ‪Norsk bokmÃ¥l‬ Polski Português РуÑ?Ñ?кий Suomi Svenska Türkçe ä¸æ–‡ This page was last modified on 5 August 2008, at 07:03
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