The striatum, or corpus striatum (also called the striate nucleus), is a

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

(a cluster of

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa ...

s) in the

subcortical The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

basal ganglia The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an ext ...

of the forebrain. The striatum is a critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources; and serves as the primary input to the rest of the basal ganglia. Functionally, the striatum coordinates multiple aspects of

cognition Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, though ...

, including both motor and action planning, decision-making,

motivation Motivation is the reason for which humans and other animals initiate, continue, or terminate a behavior at a given time. Motivational states are commonly understood as forces acting within the agent that create a disposition to engage in goal-dire ...

, reinforcement, and reward perception. The striatum is made up of the

caudate nucleus The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia in the human brain. While the caudate nucleus has long been associated with motor processes due to its role in Parkinson's d ...

and the lentiform nucleus. The lentiform nucleus is made up of the larger putamen, and the smaller globus pallidus. Strictly speaking the globus pallidus is part of the striatum. It is common practice, however, to implicitly exclude the globus pallidus when referring to striatal structures. In

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...

s, the striatum is divided into a ventral striatum, and a dorsal striatum, subdivisions that are based upon function and connections. The ventral striatum consists of the

nucleus accumbens The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hyp ...

and the

olfactory tubercle The olfactory tubercle (OT), also known as the tuberculum olfactorium, is a multi-sensory processing center that is contained within the olfactory cortex and ventral striatum and plays a role in reward cognition. The OT has also been shown to ...

. The dorsal striatum consists of the

and the putamen. A

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribu ...

, nerve tract (the internal capsule) in the dorsal striatum separates the

and the putamen. Anatomically, the term ''striatum'' describes its striped (striated) appearance of grey-and-white matter.

Structure

The striatum is the largest structure of the

. The striatum is divided into a ventral and a dorsal subdivision, based upon function and connections. The ventral striatum is composed of the

and the

. The nucleus accumbens is made up of the

nucleus accumbens core The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypo ...

and the

nucleus accumbens shell The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypo ...

, which differ by neural populations. The olfactory tubercle receives input from the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex ...

but has not been shown to play a role in processing smell. In non-primate species, the

islands of Calleja The islands of Calleja (; IC, ISC, or IClj) are a group of neural granule cells located within the ventral striatum in the brains of most animals. This region of the brain is part of the limbic system, where it aids in the reinforcing effects of ...

are included. The ventral striatum is associated with the limbic system and has been implicated as a vital part of the circuitry for decision making and reward-related behavior. The dorsal striatum is composed of the

and the putamen.

Staining Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in th ...

can differentiate the striatum into two distinct compartments of striosomes or ''patches'', and a surrounding

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

; this is particularly evident on the components of acetylcholinesterase and calbindin. More studies have been carried out on the dorsal striatum but the compartments have also been identified in the ventral striatum. In the dorsal striatum striosomes make up 10-15 per cent of the striatal volume.

Cell types

Types of cells in the striatum include: *

Medium spiny neurons Medium spiny neurons (MSNs), also known as spiny projection neurons (SPNs), are a special type of GABAergic inhibitory cell representing 95% of neurons within the human striatum, a basal ganglia structure. Medium spiny neurons have two primary ...

(MSNs), which are the principal neurons of the striatum. They are GABAergic and, thus, are classified as inhibitory neurons. Medium spiny projection neurons comprise 95% of the total neuronal population of the human striatum. Medium spiny neurons have two characteristic types: D1-type MSNs and D2-type MSNs. A subpopulation of MSNs contain both D1-type and D2-type receptors, with approximately 40% of striatal MSNs expressing both DRD1 and DRD2

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the ...

. * Cholinergic interneurons release acetylcholine, which has a variety of important effects in the striatum. In humans, other primates, and rodents, these interneurons respond to salient environmental stimuli with stereotyped responses that are temporally aligned with the responses of dopaminergic neurons of the

substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra ap ...

. The large aspiny cholinergic interneurons themselves are affected by dopamine through D5 dopamine receptors. Dopamine also directly controls communication between cholinergic interneurons. * There are many types of GABAergic interneurons. The best known are parvalbumin expressing interneurons, also known as fast-spiking interneurons, which participate in powerful feedforward inhibition of principal neurons. Also, there are GABAergic interneurons that express

tyrosine hydroxylase Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA). It does so using molecular oxygen (O2), as well as iron (Fe2+) and t ...

, somatostatin,

nitric oxide synthase Nitric oxide synthases () (NOSs) are a family of enzymes catalyzing the production of nitric oxide (NO) from L-arginine. NO is an important cellular signaling molecule. It helps modulate vascular tone, insulin secretion, airway tone, and perist ...

and neuropeptide-y. Recently, two types of neuropeptide-y expressing GABAergic interneurons have been described in detail, one of which translates synchronous activity of cholinergic interneurons into inhibition of principal neurons. These

s of the striatum are not distributed evenly. There are two regions of neurogenesis in the brain – the subventricular zone in the lateral ventricles, and the dentate gyrus in the hippocampal formation.

Neuroblast In vertebrates, a neuroblast or primitive nerve cell is a postmitotic cell that does not divide further, and which will develop into a neuron after a migration phase. In invertebrates such as ''Drosophila,'' neuroblasts are neural progenitor cell ...

s that form in the lateral ventricle adjacent to the striatum, integrate in the striatum. This has been noted in the human striatum following an ischemic stroke. Injury caused to the striatum stimulates the migration of neuroblasts from the subventricular zone, to the striatum, where they differentiate into adult neurons. The normal passage of SVZ neuroblasts is to the

but this traffic is diverted to the striatum after an ischemic stroke. However, few of the new developed neurons survive.

Inputs

The largest connection is from the cortex, in terms of cell axons. Many parts of the

neocortex The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, sp ...

innervate the dorsal striatum. The cortical pyramidal neurons projecting to the striatum are located in layers II-VI, with the most dense projections come from layer V. They end mainly on the dendritic spines of the spiny neurons. They are glutamatergic, exciting striatal neurons. The striatum is seen as having its own internal microcircuitry. The ventral striatum receives direct input from multiple regions in the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting o ...

and limbic structures such as the

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex ver ...

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all direct ...

, and

hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...

, as well as the

entorhinal cortex The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.Integrating time from experience in th ...

and the inferior temporal gyrus. Its primary input is to the

system. Additionally, the

mesolimbic pathway The mesolimbic pathway, sometimes referred to as the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain. The ven ...

projects from the

ventral tegmental area The ventral tegmental area (VTA) (tegmentum is Latin for ''covering''), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is the ...

to the

of the ventral striatum. Another well-known afferent is the

nigrostriatal The nigrostriatal pathway is a bilateral dopaminergic pathway in the brain that connects the substantia nigra pars compacta (SNc) in the midbrain with the dorsal striatum (i.e., the caudate nucleus and putamen) in the forebrain. It is one of the fou ...

connection arising from the neurons of the

pars compacta. While cortical axons synapse mainly on spine heads of spiny neurons, nigral axons synapse mainly on spine shafts. In primates, the thalamostriatal afferent comes from the central median-parafascicular complex of the

(see primate basal ganglia system). This afferent is glutamatergic. The participation of truly intralaminar neurons is much more limited. The striatum also receives afferents from other elements of the basal ganglia such as the

subthalamic nucleus The subthalamic nucleus (STN) is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system. In terms of anatomy, it is the major part of the subthalamus. As suggested by its name, the ...

(glutamatergic) or the

external globus pallidus The external globus pallidus (GPe or lateral globus pallidus) combines with the internal globus pallidus (GPi) to form the globus pallidus, an anatomical subset of the basal ganglia. Globus pallidus means "pale globe" in Latin, indicating its appea ...

( GABAergic).

Targets

The primary outputs of the ventral striatum project to the ventral pallidum, then the

medial dorsal nucleus The medial dorsal nucleus (or dorsomedial nucleus of thalamus) is a large nucleus in the thalamus. It is believed to play a role in memory. Structure It relays inputs from the amygdala and olfactory cortex and projects to the prefrontal corte ...

of the

, which is part of the frontostriatal circuit. Additionally, the ventral striatum projects to the globus pallidus, and substantia nigra pars reticulata. Some of its other outputs include projections to the extended amygdala, lateral hypothalamus, and

pedunculopontine nucleus The pedunculopontine nucleus (PPN) or pedunculopontine tegmental nucleus (PPT or PPTg) is a collection of neurons located in the upper pons in the brainstem. It lies caudal to the substantia nigra and adjacent to the superior cerebellar pedunc ...

. Striatal outputs from both the dorsal and ventral components are primarily composed of

medium spiny neuron Medium spiny neurons (MSNs), also known as spiny projection neurons (SPNs), are a special type of GABAergic inhibitory cell representing 95% of neurons within the human striatum, a basal ganglia structure. Medium spiny neurons have two primar ...

s (MSNs), a type of projection neuron, which have two primary

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...

s: "indirect" MSNs that express D2-like receptors and "direct" MSNs that express D1-like receptors. The main nucleus of the basal ganglia is the striatum which projects directly to the globus pallidus via a pathway of striatopallidal fibers. The striato-pallidal pathway has a whitish appearance due to the myelinated fibers. This projection comprises successively the external globus pallidus (GPe), the internal globus pallidus (GPi), the pars compacta of the

(SNc), and the pars reticulata of substantia nigra (SNr). The neurons of this projection are inhibited by GABAergic synapses from the dorsal striatum. Among these targets, the GPe does not send axons outside the system. Others send axons to the superior colliculus. Two others comprise the output to the thalamus, forming two separate channels: one through the internal segment of the globus pallidus to the ventral oralis nuclei of the thalamus and from there to the cortical supplementary motor area and another through the substantia nigra to the ventral anterior nuclei of the thalamus and from there to the

frontal cortex The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove be ...

and the occulomotor cortex.

Blood supply

Deep penetrating striate arteries supply blood to the striatum. These arteries include the recurrent artery of Heubner arising from the

anterior cerebral artery The anterior cerebral artery (ACA) is one of a pair of cerebral arteries that supplies oxygenated blood to most midline portions of the frontal lobes and superior medial parietal lobes of the brain. The two anterior cerebral arteries arise from ...

, and the

lenticulostriate arteries The lenticulostriate arteries, anterolateral central arteries, or antero-lateral ganglionic branches are a group of small arteries arising from the initial part M1 of the middle cerebral artery that supply the basal ganglia. Structure The lenticul ...

arising from the middle cerebral artery.

Function

The ventral striatum, and the

in particular, primarily mediates reward, cognition, reinforcement, and

motivational salience Motivational salience is a cognitive process and a form of attention that ''motivates'' or propels an individual's behavior towards or away from a particular object, perceived event or outcome. Motivational salience regulates the intensity of b ...

, whereas the dorsal striatum primarily mediates cognition involving motor function, certain

executive functions In cognitive science and neuropsychology, executive functions (collectively referred to as executive function and cognitive control) are a set of cognitive processes that are necessary for the cognitive control of behavior: selecting and su ...

(e.g., inhibitory control and impulsivity), and stimulus-response learning; there is a small degree of overlap, as the dorsal striatum is also a component of the

reward system The reward system (the mesocorticolimbic circuit) is a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), associative learning (primarily positive reinforcement and cla ...

that, along with the

, mediates the encoding of new motor programs associated with future reward acquisition (e.g., the conditioned motor response to a reward cue). Metabotropic dopamine receptors are present both on spiny neurons and on cortical axon terminals.

Second messenger Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form or cell signaling, encompassing both first m ...

cascades triggered by activation of these dopamine receptors can modulate pre- and postsynaptic function, both in the short term and in the long term. In humans, the striatum is activated by stimuli associated with reward, but also by

aversive In psychology, aversives are unpleasant stimuli that induce changes in behavior via negative reinforcement or positive punishment. By applying an aversive immediately before or after a behavior the likelihood of the target behavior occurring in t ...

, novel, unexpected, or intense stimuli, and cues associated with such events.

fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area ...

evidence suggests that the common property linking these stimuli, to which the striatum is reacting, is salience under the conditions of presentation. A number of other brain areas and circuits are also related to reward, such as frontal areas. Functional maps of the striatum reveal interactions with widely distributed regions of the cerebral cortex important to a diverse range of functions. The interplay between the striatum and the

prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA ...

is relevant for behavior, particularly adolescent development as proposed by the

dual systems model The dual systems model, also known as the maturational imbalance model, is a theory arising from developmental cognitive neuroscience which posits that increased risk-taking during adolescence is a result of a combination of heightened reward sensi ...

Clinical significance

Parkinson's disease and other movement disorders

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms beco ...

results in loss of dopaminergic innervation to the dorsal striatum (and other basal ganglia) and a cascade of consequences. Atrophy of the striatum is also involved in

Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...

, and movement disorders such as chorea, choreoathetosis, and

dyskinesias Dyskinesia refers to a category of movement disorders that are characterized by involuntary muscle movements, including movements similar to tics or chorea and diminished voluntary movements. Dyskinesia can be anything from a slight tremor of t ...

. These have also been described as ''circuit disorders'' of the basal ganglia.

Addiction

Addiction Addiction is a neuropsychological disorder characterized by a persistent and intense urge to engage in certain behaviors, one of which is the usage of a drug, despite substantial harm and other negative consequences. Repetitive drug use o ...

, a disorder of the brain's

, arises through the overexpression of DeltaFosB (ΔFosB), a

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...

, in the D1-type

s of the ventral striatum. ΔFosB is an inducible gene which is increasingly expressed in the

as a result of repeatedly

overdosing A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended.

on an addictive drug or overexposure to other addictive stimuli.
Table 1
/ref>

Bipolar disorder

An association has been observed between striatal expression of variants of the PDE10A gene and some bipolar I disorder patients. Variants of other genes, DISC1 and GNAS, have been associated with

bipolar II disorder Bipolar II disorder (BP-II) is a mood disorder on the bipolar spectrum, characterized by at least one episode of hypomania and at least one episode of major depression. Diagnosis for BP-II requires that the individual must never have experien ...

Autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by cognitive inflexibility and poor understanding of social systems. This inflexible behavior originates in defects in the pre-frontal cortex as well as the striatal circuits. The defects in the striatum seem to specifically contribute to the motor, social and communication impairments seen in ASD patients. In mice which have an ASD-like phenotype induced via the overexpression of the eukaryotic initiation of translation factor 4E, it has been shown that these defects seem to stem from the reduced ability to store and process information in the striatum, which leads to the difficulty seen in forming new motor patterns, as well as disengaging from existing ones.

Dysfunction

Dysfunction in the ventral striatum can lead to a variety of disorders, most notably, depression and obsessive-compulsive disorder. Because of its involvement in reward pathways, the ventral striatum has also been implicated in playing a critical role in addiction. It has been well established that the ventral striatum is strongly involved in mediating the reinforcing effects of drugs, especially stimulants, through dopaminergic stimulation.

History

In the seventeenth and eighteenth centuries, the term "corpus striatum" was used to designate many distinct, deep, infracortical elements of the hemisphere. Etymologically it is derived from (Latin) "striatus" = "grooved, striated" and the English "striated" = having parallel lines or grooves on the surface. In 1876

David Ferrier Sir David Ferrier FRS (13 January 1843 – 19 March 1928) was a pioneering Scottish neurologist and psychologist. Ferrier conducted experiments on the brains of animals such as monkeys and in 1881 became the first scientist to be prosecuted ...

contributed decades of research to the subject; concluding that the corpus striatum was vital in the "organization and generation of voluntary movement". In 1941, Cécile and Oskar Vogt simplified the nomenclature by proposing the term ''striatum'' for all elements in the

built with striatal elements: the

, the putamen, and the fundus striati, which is the ventral part linking the two preceding 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 Medical Subject Headings.

Other animals

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s the term used was the ''paleostriatum augmentatum'', and in the new avian terminology listing (as of 2002) for ''neostriatum'' this has been changed to the '' nidopallium''. In non-primate species, the

are included in the ventral striatum.

Additional images

File:Striatum coronal sections.gif, Striatum highlighted in green on coronal T1 MRI images File:Striatum sagittal sections.gif, Striatum highlighted in green on sagittal T1 MRI images File:Striatum transversal sections.gif, Striatum highlighted in green on transversal T1 MRI images

References

External links

* * * * https://web.archive.org/web/20131029195257/http://www.nimh.nih.gov/images/news-items/r1_braindorsal1.jpg * https://web.archive.org/web/20090914200329/http://www.hnl.bcm.tmc.edu/fmri.html {{Authority control Cerebrum Basal ganglia Addiction

Structure

Cell types

Inputs

Targets

Blood supply

Function

Clinical significance

Parkinson's disease and other movement disorders

Addiction

Bipolar disorder

Autism spectrum disorder

Dysfunction

History

Other animals

See also

Additional images

References

External links