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07-SEPTEMBER-2008 03:17:44 - Striatum Brain: Striatum Image:CoronalStriatumGP.PNG Coronal slices of human brain showing the basal ganglia, the striatum and globus pallidus The striatum green NeuroNames hier-207 The striatum is a subcortical i.e. inside, rather than on the outside part of the telencephalon. It is the major input station of the basal ganglia system. Anatomically, the striatum is the caudate nucleus and the putamen.1 Contents 1 History 2 Structure 3 Organization 3.1 Anatomical subdivisions and territories 3.2 Compartments 4 Afferent Connections 5 Targets 6 Function 7 Pathology 8 Additional images 9 References 10 Further reading 11 See also 12 External links History In the seventeenth and eighteenth centuries, the term corpus striatum was used to designate many distinct, deep, infracortical elements of the hemisphere i.e. Vieussens, 1685. The Vogts Cécile and Oskar, 1941 simplified the nomenclature by proposing the term striatum for all elements built with striatal elements see Primate basal ganglia system: the caudate, the putamen and the fundus striati, that ventral part linking the two precedings together ventrally to the inferior part of the internal capsule. The term neostriatum was forged by comparative anatomists comparing the subcortical structures between vertebrates because it was thought to be a phylogenetically newer section of the corpus striatum. The term is still used by some sources, including MeSH.2 Structure The dorsal striatum forms a continuous and large mass, topographically separated by the internal capsule into the caudate nucleus medially, the putamen laterally and the fundus below, linking the two preceding ventrally; but a single entity. The striatum is homogeneous in terms of neuronal components. It is built up of 4 neuronal types:3 spiny neurons relatively close from the pyramidal neurons of the cortex due to the presence of spines with spine apparatus acanthodendritic neurons, and make up 96% of the striatum. Leptodendritic Deiter's neurons2% with large, poorly bifurcated, arborisations looking like pallidonigral neurons. Spidery cholinergic interneurons1% morphologically entirely different from those observed in rodents which must lead to very careful interspecific correlations.In primates they are the Tonically Active Neurons TANs. These briefly stop firing in concomitance to behaviourally salient situations and reward-related events. GABAergic parvalbumin expressing interneurons, which are fast-spiking, and express dopamine receptors GABAergic calretinin expressing interneurons GABAergic somatostatin expressing interneurons, which are low threshold spiking and express dopamine receptors Organization The striatum is spatially organized according to several levels. Anatomical subdivisions and territories The dorsal striatum is a single entity closed and continuous with a toric topology. The observable anatomical subdivisions of the dorsal striatum caudate nucleus and putamen essentially induced by the internal capsule do not completely overlap with now accepted anatomo-functional subdivisions. The selective distribution of the axonal terminal arborisations of cortical sources differentiate the sensorimotor striatum, mainly putaminal but located in its dorsal part and in the lateroinferior part of the caudate. A great part of the remaining of the volume essentially caudate receiving from axonal endings from the frontal, parietal, temporal cortex forms the associative striatum. The separation between these two territories is rather clearcut and observable using calbindin immunochemistry. A third entity, the most inferomedial, raises more problems as there is no general agreement about its border with the associative striatum. The ventral striatum is clearly delineated by tracing the subicular territory. This corresponds to the olfactory tubercle and the nucleus accumbens, which is not a nucleus and is a striatal part made up of striatal elements. More information on the anatomical divisions of the striatum can be found in Voorn et al. 20044. Compartments Immunochemical characteristics particularly acetyl cholinesterase differentiated compartments called 'striosomes' and matrix in which 'matrisomes'are sometimes differentiated. Afferent Connections The most important afferent in terms of quantity of axons is the corticostriatal connection. Many parts of the neocortex innervate the dorsal striatum. The cortical pyramidal neurons projecting to the striatum are located in the lamina V. They end mainly on the spines of the spiny neurons. They are glutamatergic, exciting striatal neurons. Another well known afferent is the nigrostriatal connection arising from the neurons of the substantia nigra pars compacta. While cortical axons synapse mainly on spine heads of spiny neurons, nigral axons synapse mainly on spine shafts. The thalamostriatal afferent essentially comes in primates from the central region center median parafascicular complex see primate basal ganglia system.This is glutamatergic. The participation of truly intralaminar neurons is much more limited. The striatum receives afferents from other elements of the basal ganglia such as the subthalamic nucleus glutamatergic or the external globus pallidus GABAergic. Targets The main efferent target of the striatum is the pallidonigral set.The basal ganglia core is made up of the striatum and its direct targets through the striato-pallidonigral bundle. The striato-pallidonigral bundle is a very dense bundle of fewly myelinated axons giving the whitish aspect to the set. This comprises successively the external globus pallidus GPe, the internal globus pallidus GPi, the pars compacta of the substantia nigra SNc and the substantia nigra pars reticulata SNr. This set is made up of the same genus of neurons. Its neurons are inhibited by GABAergic synapses from the dorsal striatum. Among these targets, one does not send axons outside the system GPe, thus a regulator. Another sends axons to the superior colliculus. Two others are the bases of basal ganglia system output to the thalamus forming two separate channels: one through the internal segment of the globus pallidus to VO and from there to the cortical SMA and another through the substantia nigra to VA and from there to the frontal and the oculomotor cortex . Function Metabotropic dopamine receptors are present both on spiny neurons and on cortical axon terminals. Second messenger cascades triggered by activation of these dopamine receptors can modulate pre- and postsynaptic function, both in the short term and in the long term. The striatum is best known for its role in the planning and modulation of movement pathways but is also involved in a variety of other cognitive processes involving executive function. In humans the striatum is activated by stimuli associated with reward, but also by aversive, novel, unexpected or intense stimuli, and cues associated with such events. Recent fMRI evidencecitation needed suggests that the common property linking these stimuli, to which the striatum is reacting, is saliency under the conditions of presentation. A number of other brain areas and circuits are also related to reward such as frontal areas. Research at the Wellcome Trust Centre for Neuroimaging at UCL University College London shows it to be associated with novelty-related decision making behaviors. For sources regarding saliency of the reward pathway thought to be related to dopamine one can look to the work of Dr. John D. Salamone early to late 1990s and Wolfram Shultz.5 The ventral tegmental dopaminergic neurons that innervate portions of the striatum have long been accepted to be the site of rewarding feeling. Intracranial stimulation studies from the 1960s show implants in this brain area will elicit bar pressing from rats for many hours at a time. However the collective works of researchers in the 1990s show that blocking dopamine receptors does not remove rewarding sensations, rather it effects how much the animal is willing to work, more motivation to seek reward rather than reward itself. Pathology Parkinson's disease results in loss of dopaminergic innervation to the striatum and other basal ganglia and a cascade of subsequent consequences. The lesion of the striatum is also involved in Huntington's disease, choreas, choreoathetosis and dyskinesias. It is also thought that addiction involves plasticity at striatal synapses. Additional images Dopamine and serotonin References ^ DBS: The Basal Ganglia. ^ MeSH Neostriatum ^ Yelnik J, Francois C, Percheron G. Spatial relationships between striatal axonal endings and pallidal neurons in macaque monkeys. Adv Neurol. 1997;74:45-56. PMID 9348401. ^ Pieter Voorn, Louk J. M. JVanderschuren, Henk J. Groenewegen, Trevor W. Robbins and Cyriel M. A. Pennartz, Putting a spin on the dorsal-ventral divide of the striatum, Trends in Neurosciences, Volume 27, Issue 8, 1 August 2004, Pages 468-474. ^ Department of Physiology, Development and Neuroscience: About the Department. Further reading Aosaki T, Kiuchi K Kawaguchi Y 1998 Dopamine D1-like receptor activation excites rat striatal large aspiny neurons in vitro. J Neurosci 15, 5180-90 Apicella P 2002 Tonically active neurons in the primate striatum and their role in the processing of information about motivationally relevant events. Eur J Neurosci 16, 2017-26 Cossette, M., Lecomte, F. and Partent, A. 2005 Morphology and distribution of dopaminergic intrinsic to human striatum. J. Chem. Neuroanat. 29: 1-11 Holt DJ, Graybiel AM Saper CB 1997 Neurochemical architecture of the human striatum. J Comp Neurol 21, 1-25 Morris G, Arkadir D, Nevet A, Vaadia E Bergman H 2004 Coincident but distinct messages of midbrain dopamine and striatal tonically active neurons. Neuron 8, 133-43 Tepper JM Bolam JP 2004 Functional diversity and specificity of neostriatal interneurons. Curr Opin Neurobiol 14, 685-92 Yamada H, Matsumoto N Kimura M 2004 Tonically active neurons in the primate caudate nucleus and putamen differentially encode instructed motivational outcomes of action. J Neurosci 7, 3500-10 Yelnik, J., François, C., Percheron, G., Tandé, D. 1991 Morphological taxonomy of the neurons of the primate striatum. J. Comp. Neurol. 313:273-294 Zink, CF, Pagnoni G, Martin-Skurski ME, Chappelow JC, Berns GS 2004. Human striatal responses to monetary reward depend on saliency. Neuron 42, 509-17 See also List of regions in the human brain External links BrainMaps at UCDavis striatum NeuroNames hier-207 MeSH Corpus+Striatum 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/Striatum Categories: CerebrumHidden categories: All articles with statements | Articles with statements since February 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 Català Deutsch Español Français Italiano עברית 日本語 Polski 中文 This page was last modified on 29 August 2008, at 12:59
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