@prefix : .
@prefix BIRNLEX: .
@prefix MBA: .
@prefix NIFEXT: .
@prefix NLXCELL: .
@prefix NLXMOL: .
@prefix owl: .
@prefix PR: .
@prefix rdf: .
@prefix rdfs: .
@prefix SAO: .
@prefix SCR: .
@prefix skos: .
@prefix UBERON: .
@prefix xml: .
@prefix xsd: .
a owl:Ontology ;
rdfs:label "Knolwedge Space Defs" ;
skos:altLabel "KSDEFS" ;
rdfs:comment "Definitions from knowledge space descriptions. Generated by pyontutils/ksdesc_bridge.py" ;
owl:versionInfo "2016-11-14" .
### Annotations
BIRNLEX:796 skos:definition """This is the brain.
Most vertebrates and invertebrates have brains.
""" .
BIRNLEX:826 skos:definition """The basal ganglia comprise two principal input nuclei, the striatum and the subthalamic nucleus (STN), and two principal output nuclei, the substantia nigra pars reticulata (SNr) and the internal globus pallidus (GPi) (primates) which in cats and rodents is known as the entopeduncular nucleus ( Figure 1). The external globus pallidus (GPe) is principally an intrinsic structure that receives most of its afferents from, and provides efferent connections to other basal ganglia nuclei. Finally, dopaminergic neurones in substantia nigra (pars compacta) (SNc) and the adjacent ventral tegmental area (VTA) provide other basal ganglia nuclei, principally the striatum, with important modulatory signals.
from Peter Redgrave (2007) [Basal Ganglia](http://www.scholarpedia.org/article/Basal_ganglia) - [Scholarpedia](http://www.scholarpedia.org/Scholarpedia)
The basal ganglia (or basal nuclei) comprise multiple subcortical nuclei, of varied origin, in the brains of vertebrates, which are situated at the base of the forebrain. Basal ganglia nuclei are strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas. The basal ganglia are associated with a variety of functions including: control of voluntary motor movements, procedural learning, routine behaviors or "habits" such as bruxism, eye movements, cognition and emotion.
[Basal Ganglia - Wikipedia](https://en.wikipedia.org/wiki/Basal_ganglia)
""" .
BIRNLEX:954 skos:definition """The thalamus is a paired subcortical brain structure joined at the midline and sitting very near the center of the brain. In the human, each half is roughly the size and shape of a walnut. There are two major components. First is the dorsal thalamus, which is comprised of roughly 15 nuclei with relay cells that project to the cerebral cortex. (By "cortex" in this account, we mean "[neocortex](http://knowledge-space.org/wiki/UBERON:0001950).") Second is the ventral thalamus, the major portion of which is the [thalamic reticular nucleus](http://knowledge-space.org/wiki/UBERON:0001903), which sits like a shield flush against the lateral surface of the dorsal thalamus; reticular cells are GABAergic and project into the dorsal thalamus to inhibit relay cells. The other cellular component of thalamus, in addition to relay and reticular cells, is interneurons, which are also GABAergic, sit amongst the relay cells, and inhibit them. Generally, the relay cell to interneuron ratio is between 3 and 4 to one. An exception is found the mouse and rat, in which interneurons are essentially missing from all thalamic nuclei except the lateral geniculate nucleus ([Arcelli et al, 1997](https://www.ncbi.nlm.nih.gov/pubmed/8978932)).
Most of the relay nuclei topographically innervate the middle layers of cortex, but a few along the midline and extended between other nuclei project rather diffusely to upper cortical layers, including layer 1; rather little is known of these latter, diffusely-projecting nuclei, and they are not further considered in this account (for further details, see Sherman and Guillery, 2006; Jones, 2006). The remaining thalamic relay nuclei each innervates one or a small number of cortical areas. Indeed, all information reaching cortex passes through thalamus, and thus thalamus sits in a strategic position for brain processing.
The major role of thalamus is to gate and otherwise modulate the flow of information to cortex. For example, visual information from the retina is not sent directly to visual cortex but instead is relayed through the lateral geniculate nucleus of the thalamus. In the macaque monkey, there are roughly 1x10^6 geniculate relay cells ([Williams and Rakic, 1988](https://www.ncbi.nlm.nih.gov/pubmed/3417894)), but in primary visual cortex there are roughly 1.6x10^8 neurons ([O'Kusky and Colonnier, 1982](https://www.ncbi.nlm.nih.gov/pubmed/7142443)), which is typical of thalamocortical relationships. Thus thalamus represents the final bottleneck of information flow before it gets into cortex. In other words, to modify information flow for processes of attention and other behavioral requirements, it is more efficient to do this at the level of thalamus before it reaches cortex. While there is still much to learn about the cell and circuit properties of thalamus in this role, what we do know supports this general view of thalamic function. For further details of thalamus, see Jones (2006) and Sherman and Guillery (2006).
Adapted from [S. Murray Sherman (2006), Scholarpedia, 1(9):1583](http://www.scholarpedia.org/article/Thalamus).
""" .
MBA:549 skos:definition "The [thalamus](http://www.knowledge-space.org/wiki/UBERON:0001897) as delineated by the Allen Mouse Brain Atlas. Note that compared to the generic definition, the Mouse Brain Atlas considers the reticular nucleus of the thalamus as part of a grouping called [polymodal association cortex related thalamus](http://www.knowledge-space.org/wiki/MBA:856), rather than as part of the ventral thalamus, as in many classical hierarchies." .
NIFEXT:55 skos:definition "Martinotti cells (MCs) have mostly ovoid-shaped somata, bitufted dendritic morphologies, and axons with characteristic spiny boutons projecting to layer I and spreading horizontally across neighbouring columns more than 1 mm. MCs are somatostatin (SOM) positive, and negative for parvalbumin (PV) as well as vasoactive intestinal peptide (VIP). Calbindin (CB), calretinin (CR), neuropeptide Y (NPY) and cholecystokinin (CCK) are co-expressed with SOM in some MCs. All synapses are symmetrical and most synapses form onto dendritic shafts. MCs have been found to contact tuft, apical and basal dendrites in multiple neocortical layers: layer II/III MCs target mostly layer I and to a lesser degree layer II/III; layer IV MCs target mostly layer IV and to a lesser degree layer I; layer V and VI MCs target mostly layer IV and layer I and to a lesser degree the layer in which their somata was located. MCs typically display spike train accommodation in response to depolarizing somatic current injections, although some display non-accommodating and a few displayed irregular spiking responses and initial bursts. Accommodating responses were found in all layers, non-accommodating mostly in upper layers and bursting mostly in layer V. Some layer-specific trends seem to exist. Finally, MCs with accomodating firing have been observed to show the highest ion channels expression for (from highest to lowest); Caβ1, Kv3.3, HCN4, Caβ4, Kv3.2, Kv3.1, Kv2.1, HCN3, Caα1G, Kv3.4, Kv4.2, Kv1.1 and HCN2. [Wang et al., Cerebral Cortex, 2004](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1665344/)" .
NIFEXT:56 skos:definition """Approximately 50% of all inhibitory neocortical interneurons are basket cells. Basket cells specialize in targeting the somata and proximal dendrites of pyramidal neurons and interneurons, which places them in a unique position to adjust the gain of the integrated synaptic response. The term ‘basket cell’ comes from the basket-like appearance around pyramidal cell somata that results from convergent innervation by many basket cells. On the basis of differences in their axonal and dendritic morphologies, basket cells can be divided into three main subclasses: large basket cells (LBCs), small basket cells (SBCs) and nest basket cells (NBCs). Basket cells typically express many neuropeptides and the two calcium-binding proteins, PARVALBUMIN (PV) and CALBINDIN (CB).
adapted from Markram et al., Interneurons of the neocortical inhibitory system. Nature Reviews Neuroscience 5, 793-807 (October 2004) | doi:10.1038/nrn1519
""" .
NIFEXT:5242 skos:definition "A family of ionotropic, ligand gated ion channels with chloride conductances having physiological reversal potentials around the chloride reversal potential and relatively short time constants." .
NLXCELL:100601 skos:definition "Neuron characterized by a high density of dendritic spines on the dendrites." .
NLXMOL:20090505 skos:definition "Group II glutamate receptor. Glutamate receptor, metabotropic 2, GluR2, also known as GRM2, is a human gene." .
PR:000000705 skos:definition "A potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel protein that is a translation product of the HCN1 gene or a 1:1 ortholog thereof." .
PR:000000706 skos:definition "A potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel protein that is a translation product of the HCN2 gene or a 1:1 ortholog thereof." .
PR:000000707 skos:definition "A potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel protein that is a translation product of the HCN3 gene or a 1:1 ortholog thereof." .
SAO:408819766 skos:definition "Principal neuroglial cell of the peripheral nervous system which ensheath the peripheral axons of neurons and form myelin. Schwann cells may be myelinating or non-myelinating." .
SAO:666951243 skos:definition "Intrinsic cell residing in the inner third of the molecular layer of the cerebellar cortex. Axons extend laterally, transverse to the folium, and densely innervate the somata of Purkinje neurons. Axon collaterals of the basket cell axon form the specialized terminal plexus, the \"pinceau\", around the Purkinje cell axon initial segment. Llinas, Walton and Lang. In: The Synaptic Organization of the Brain. 5th ed. 2004." .
SAO:862606388 skos:definition "Projection neuron in the cerebral cortex, hippocampal formation and some other brain regions. Pyramidal cells have a pyramid-shaped soma with the apex and an apical dendrite pointed toward the pial surface and other dendrites and an axon emerging from the base. The axons may have local collaterals but also project outside their cortical region (MSH)." .
SAO:1417703748 skos:definition """A neuron (/ˈnjʊərɒn/ nyewr-on or /ˈnʊərɒn/ newr-on, also known as a neurone[1] or nerve cell) is an electrically excitable cell that processes and transmits information through electrical and chemical signals. These signals between neurons occur via synapses, specialized connections with other cells. Neurons can connect to each other to form neural networks. Neurons are the core components of the brain and spinal cord of the central nervous system (CNS), and of the ganglia of the peripheral nervous system (PNS). Specialized types of neurons include: sensory neurons which respond to touch, sound, light and all other stimuli affecting the cells of the sensory organs that then send signals to the spinal cord and brain, motor neurons that receive signals from the brain and spinal cord to cause muscle contractions and affect glandular outputs, and interneurons which connect neurons to other neurons within the same region of the brain, or spinal cord in neural networks.
A typical neuron consists of a cell body (soma), dendrites, and an axon. The term neurite is used to describe either a dendrite or an axon, particularly in its undifferentiated stage. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres and branching multiple times, giving rise to a complex "dendritic tree". An axon (also called a nerve fiber when myelinated) is a special cellular extension (process) that arises from the cell body at a site called the axon hillock and travels for a distance, as far as 1 meter in humans or even more in other species. Nerve fibers are often bundled into fascicles, and in the peripheral nervous system, bundles of fascicles make up nerves (like strands of wire make up cables). The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon, although the axon may branch hundreds of times before it terminates. At the majority of synapses, signals are sent from the axon of one neuron to a dendrite of another. There are, however, many exceptions to these rules: neurons that lack dendrites, neurons that have no axon, synapses that connect an axon to another axon or a dendrite to another dendrite, etc.
All neurons are electrically excitable, maintaining voltage gradients across their membranes by means of metabolically driven ion pumps, which combine with ion channels embedded in the membrane to generate intracellular-versus-extracellular concentration differences of ions such as sodium, potassium, chloride, and calcium. Changes in the cross-membrane voltage can alter the function of voltage-dependent ion channels. If the voltage changes by a large enough amount, an all-or-none electrochemical pulse called an action potential is generated, which travels rapidly along the cell's axon, and activates synaptic connections with other cells when it arrives.
[From Wikipedia](https://en.wikipedia.org/wiki/Neuron)""" .
SAO:1700719022 skos:definition "Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology (MSH)." .
SAO:2128417084 skos:definition """Principal neuron of the cerebral cortex (not including hippocampus or olfactory cortex). The pyramidal cell of the neocortex is located in layers 2-3 and 5-6, has a pyramidal-shaped cell body which gives off a number of laterally-directed basal dendrites and usually a single apical dendrite which ascends to branch and terminate in layer 1; these dendrites are covered in dendritic spines.
Features:
- Triangular shaped cell body after which the neuron is named.
- Large apical dendrite,
- Multiple basal dendrites
- High density of dendritic spines.
Neurotransmitter: Glutamate
Key molecules: AMPA receptor
Organisms: Mammal
""" .
SCR:014204 skos:definition """## For testing only
[a relative link](UBERON:0001950)
""" .
UBERON:0001874 skos:definition "Subcortical nucleus of the telencephalon, which together with the caudate nucleus, forms the striatum (or dorsal striatum). In many species, including primates and carnivores, the putamen is separated from the caudate nucleus by the fibers of the [anterior limb of the internal capsule](http://knowledge-space.org/wiki/UBERON:0014526) for most of its length, except at its anterior portion. The putamen lies lateral to the internal capsule and lateral to the [external segment of the globus pallidus](http://knowledge-space.org/wiki/UBERON:0002476). In primates, it is separated from the latter by the external medullary lamina. The putamen and the globus pallidus (both internal and external segments) collectively are sometimes referred to as the [lentiform nucleus](http://knowledge-space.org/index.php/pages/view/UBERON:0002263), although this is purely a descriptive term, as it is not a nucleus in the classic sense. The putamen is cytoarchitecturally and hodologically distinct from the globus pallidus, and therefore the lentiform nucleus represents \"an arbitrary grouping of adjacent structures\" according to Swanson ([Swanson, 2003](https://www.ncbi.nlm.nih.gov/pubmed/12724158))." .
UBERON:0001882 skos:definition """A region of the brain located in the forebrain ventral to the [caudate nucleus](http://knowledge-space.org/wiki/UBERON:0001873) and [putamen](http://knowledge-space.org/wiki/UBERON:0001874) ([caudoputamen](http://knowledge-space.org/wiki/UBERON:0005383) in rodent) and continuous with these structures. There is no distinct boundary between the nucleus accumbens and the caudate/putamen, but in rodents, it can be identified by its lack of traversing fiber bundles in comparison to the dorsal striatum. Its principle neuron is the [medium spiny neuron](http://knowledge-space.org/wiki/NIFCELL:nifext_141). Together with the neostriatum (caudate nucleus and putamen), the nucleus accumbens forms the [striatum](http://knowledge-space.org/wiki/UBERON:0002435). The nucleus accumbens and the [olfactory tubercle](http://knowledge-space.org/wiki/UBERON:0001883) collectively form the ventral striatum, which is part of the basal ganglia. It is considered by many to be the interface between motivation and movement ([Meredith et al., 2008](https://www.ncbi.nlm.nih.gov/pubmed/18256852))
As first described by Zaborsky and colleagues, the nucleus accumbens can be divided into two compartments, the core and the shell, based on connectivity, morphology and histochemistry. Behavioral studies also point to functional differences between the core and shell (reviewed in [Meredith et al., 2008](https://www.ncbi.nlm.nih.gov/pubmed/18256852).
""" .
UBERON:0001897 skos:definition """The thalamus is a paired subcortical brain structure joined at the midline and sitting very near the center of the brain. In the human, each half is roughly the size and shape of a walnut. There are two major components. First is the dorsal thalamus, which is comprised of roughly 15 nuclei with relay cells that project to the cerebral cortex. (By "cortex" in this account, we mean "[neocortex](http://www.knowledge-space.org/wiki/UBERON:0001950).") Second is the ventral thalamus, the major portion of which is the thalamic reticular nucleus, which sits like a shield flush against the lateral surface of the dorsal thalamus; reticular cells are GABAergic and project into the dorsal thalamus to inhibit relay cells. The other cellular component of thalamus, in addition to relay and reticular cells, is interneurons, which are also GABAergic, sit amongst the relay cells, and inhibit them. Generally, the relay cell to interneuron ratio is between 3 and 4 to one. An exception is found the mouse and rat, in which interneurons are essentially missing from all thalamic nuclei except the lateral geniculate nucleus (Arcelli et al, 1997).
Most of the relay nuclei topographically innervate the middle layers of cortex, but a few along the midline and extended between other nuclei project rather diffusely to upper cortical layers, including layer 1; rather little is known of these latter, diffusely-projecting nuclei, and they are not further considered in this account (for further details, see Sherman and Guillery, 2006; Jones, 2006). The remaining thalamic relay nuclei each innervates one or a small number of cortical areas. Indeed, all information reaching cortex passes through thalamus, and thus thalamus sits in a strategic position for brain processing.
The major role of thalamus is to gate and otherwise modulate the flow of information to cortex. For example, visual information from the retina is not sent directly to visual cortex but instead is relayed through the lateral geniculate nucleus of the thalamus. In the macaque monkey, there are roughly 1x10^6 geniculate relay cells (Williams and Rakic, 1988), but in primary visual cortex there are roughly 1.6x10^8 neurons (O'Kusky and Colonnier, 1982), which is typical of thalamocortical relationships. Thus thalamus represents the final bottleneck of information flow before it gets into cortex. In other words, to modify information flow for processes of attention and other behavioral requirements, it is more efficient to do this at the level of thalamus before it reaches cortex. While there is still much to learn about the cell and circuit properties of thalamus in this role, what we do know supports this general view of thalamic function. For further details of thalamus, see Jones (2006) and Sherman and Guillery (2006).
Adapted from [S. Murray Sherman (2006), Scholarpedia, 1(9):1583](http://www.scholarpedia.org/article/Thalamus).
""" .
UBERON:0001903 skos:definition """The thalamic reticular nucleus is a shell-like nucleus that forms a capsule around the thalamus laterally and anteriorally. It is separated from the thalamus by the external medullary lamina. Reticular cells are GABAergic, and have discoid dendritic arbors in the plane of the nucleus . It receives projections from the cerebral cortex and from other dorsal thalamic nuclei. It, in turn, projects to dorsal thalamic nuclei (adapted from [Wikipedia](https://en.wikipedia.org/wiki/Thalamic_reticular_nucleus)). The reticular nucleus provides the major source of GABA and inhibitory influence in the dorsal thalamus .
The reticular nucleus is traditionally considered to be part of the ventral thalamus, although this view is being questioned ([Halassa and Acsády, 2016](https://www.ncbi.nlm.nih.gov/pubmed/27589879)). The [Allen Mouse Brain Atlas](http://knowledge-space.org/wiki/MBA:549) groups it with the polymodal association nuclei-related dorsal thalamus. """ .
UBERON:0001950 skos:definition "The term neocortex refers to those areas of cerebral cortex defined on the basis of cytoarchitecture that have six layers. Starting from the cortical surface the layers are: molecular layer (I), external granular layer (II), external pyramidal layer (III), internal granular layer (IV), internal pyramidal layer (V), and multiform layer (VI). Neocortex is most prominent in the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe, less so in the cingulate gyrus, the parahippocampal gyrus and the insula. It is composed of two subdivisions: true isocortex and proisocortex (Carpenter-83)(NN)" .
UBERON:0002037 skos:definition """Part of the metencephalon that lies in the posterior cranial fossa behind the brain stem. It is concerned with the coordination of movement[MESH]. A large dorsally projecting part of the brain concerned especially with the coordination of muscles and the maintenance of bodily equilibrium, situated between the brain stem and the back of the cerebrum , and formed in humans of two lateral lobes and a median lobe[BTO]. Brain structure derived from the anterior hindbrain, and perhaps including posterior midbrain. The cerebellum plays a role in somatic motor function, the control of muscle tone, and balance[ZFA].
from Scholarpedia - [Cerebellum](http://www.scholarpedia.org/article/Cerebellum)
The cerebellum derives its name as a diminutive of the word "cerebrum". This is particularly explicit in German, where the cerebellum is called Kleinhirn ("small brain"). This structure, present in all vertebrates, occupies a position immediately behind the tectal plate and straddles the midline as a bridge over the fourth ventricle. In addition, it is the only region of the nervous system to span the midline without interruption. Technically, the output of the cerebellum is exclusively inhibitory through the Purkinje neurons onto the cerebellar nuclei, but the cerebellar nucleus exerts both excitatory and inhibitory influences, on the thalamus and on the Inferior Olive, respectively (Ruigrok and Voogd, 1995).
The cerebellum has undergone enormous elaboration throughout phylogeny, in fact, more so than any other region of the central nervous system (CNS), but has maintained its initial neuronal structure, almost invariant. Thus, its size but not its wiring has changed with CNS evolution. As an example, the cerebellar cortex in a frog has an area approximately 12 mm2 that is, 4 mm wide (in the mediolateral direction) and 3 mm long (in the rostrocaudal direction). In humans, the cerebellar cortex is a single continuous sheet with an area of 500 cm2 (1,000 mm long and 50 mm wide) . This is 4 x 10^3 times more extensive than that of a frog (Braitenberg & Atwood, 1958). The increase in cortical extent has resulted in folding into very deep folia (Figure 2), allowing this enormous surface to be packed into a volume of 6 cm x 5 cm x 10 cm. Because the cerebellar cortex extends mainly rostro-caudally, most of the foldings occur in that direction.""" .
UBERON:0002263 skos:definition "The lentiform nucleus or lenticular nucleus comprises the putamen and the globus pallidus within the basal ganglia in some species, e.g., humans, where this set of structures form a large, cone-shaped mass of gray matter just lateral to the internal capsule. The lenticular nucleus can be considered purely a descriptive term, as it is not a nucleus in the classic sense. The putamen is cytoarchitecturally and hodologically distinct from the globus pallidus. Swanson ([Swanson, 2003](https://www.ncbi.nlm.nih.gov/pubmed/12724158))refers to the lentiform nucleus as \"an arbitrary grouping of adjacent structures\"." .
UBERON:0002435 skos:definition """The striatum is the largest nucleus of the basal ganglia. In primates the striatum comprises the [caudate nucleus](http://knowledge-space.org/wiki/UBERON:0001873) and the [putamen](http://knowledge-space.org/wiki/UBERON:0001874), and in all mammals, the ventral striatum or [nucleus accumbens](http://knowledge-space.org/wiki/UBERON:0001882) (Gerfen and Wilson 1996, [Voorn et al. 2004](https://www.ncbi.nlm.nih.gov/pubmed/15271494)). It receives direct input from most regions of the cerebral cortex and limbic structures including the amygdala and hippocampus. Additional input from sensorimotor and motivational regions of the brainstem arrives indirectly via relays in the thalamus. Finally, important modulatory afferents come from substantia nigra pars compacta (dopamine) and the raphe nuclei (serotonin) in the midbrain. The striatum is subdivided into sectors along a ventromedial-dorsolateral continuum largely on the basis of external connectivity ([Voorn et al. 2004](https://www.ncbi.nlm.nih.gov/pubmed/15271494)). All regions of the striatum are divided further into regions of patch/striosomes and matrix, again on the basis of differential connectivity and distribution of neurochemical markers (Gerfen and Wilson 1996). The principal cell type (representing >90% of all neurones) in all striatal regions is the GABAergic medium spiny neuron. Spiny neurons have been separated into two further populations according to which neuroactive peptide they contain (Substance P and dynorphin or enkephalin) and the relative proportions of D1- and D2-type dopamine receptors they express. Striatal medium spiny neurones are GABAergic providing inhibitory inputs to adjacent spiny neurones via local axon collaterals, to the globus pallidus (external), and to both basal ganglia output nuclei. The remaining 5-10% of neurones in the striatum (fewer in rodents, more in primates) are either GABAergic or cholinergic interneurons, which can be distinguished according to neurochemical and in some cases morphological characteristics (for precise details of relative numbers see - [Tepper and Bolam 2004](https://www.ncbi.nlm.nih.gov/pubmed/15582369)).
modified from Peter Redgrave (2007) [Basal Ganglia](http://www.scholarpedia.org/article/Basal_ganglia). [Scholarpedia](http://www.scholarpedia.org/Scholarpedia)""" .
UBERON:0002476 skos:definition """The more lateral of the two segments of the [globus pallidus](http://knowledge-space.org/wiki/UBERON:0001875), abutting the putamen laterally in primates and the medial globus pallidus medially. It is also known as the external segment of the globus pallidus. It is distinguished from the [medial (internal) segment of the globus pallidus](http://knowledge-space.org/wiki/UBERON:0002477) by intense staining for enkephalin, due to a heavy projection from enkephalin-containing striatal medium spiny neurons ([DiFiacco et al., 1982](https://www.ncbi.nlm.nih.gov/pubmed/6275943)). The external segment of the globus pallidus is also distinguished by its efferent projections to the subthalamic nucleus, as opposed to the thalamus and substantia nigra. It is considered an integral part of the indiect pathway through the basal ganglia, in a model of basal ganglia circuitry first proposed by Albin and colleagues ([1989](https://www.ncbi.nlm.nih.gov/pubmed/2479133)).
## Delineations
-Allen Mouse Brain Atlas (MBA): [Globus pallidus, external segment](http://knowledge-space.org/wiki/MBA:1022)""" .
UBERON:0009835 skos:definition "The frontal part of the cingulate cortex that resembles a collar form around the corpus callosum. It includes both the ventral and dorsal areas of the cingulate cortex. http://en.wikipedia.org/wiki/File:Gray727.svg" .
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