The external capsule is a series of

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 distribution ...

fiber tracts in the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. These fibers run between the most lateral (toward the side of the head) segment of the

lentiform nucleus The lentiform nucleus, or lenticular nucleus, comprises the putamen and the globus pallidus within the basal ganglia. With the caudate nucleus, it forms the dorsal striatum. It is a large, lens-shaped mass of gray matter just lateral to the inter ...

(more specifically the

putamen The putamen (; from Latin, meaning "nutshell") is a round structure located at the base of the forebrain (telencephalon). The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that compose the basal n ...

) and the

claustrum The claustrum (Latin, meaning "to close" or "to shut") is a thin, bilateral collection of neurons and supporting glial cells, that connects to cortical (e.g., the pre-frontal cortex) and subcortical regions (e.g., the thalamus) of the brain. It ...

. The white matter of the external capsule contains fibers known as corticocortical

association fibers Association fibers are axons that connect cortical areas within the same cerebral hemisphere. In human neuroanatomy, axons (nerve fibers) within the brain, can be categorized on the basis of their course and connections as association fibers, ...

. These fibers are responsible for connecting 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 of ...

to another cortical area. The capsule itself appears as a thin white sheet of white matter. The external capsule is a route for

cholinergic Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word "choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation. F ...

fibers from the

basal forebrain Part of the human brain, the basal forebrain structures are located in the forebrain to the front of and below the striatum. They include the ventral basal ganglia (including nucleus accumbens and ventral pallidum), nucleus basalis, diagonal band ...

to the

. The putamen separates the external capsule from the

internal capsule The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the g ...

medially and the claustrum separates it from the

extreme capsule The extreme capsule (Latin: capsula extrema) is a series of nerve tracts between the claustrum and the insular cortex. It is also described as a thin capsule of white matter as association fibres. The extreme capsule is separated from the external ...

laterally. But the external capsule eventually joins the

around the lentiform nucleus.

Additional images

File:Gray682.png, Superficial dissection of brain-stem. Lateral view. File:Gray689.png, Superficial dissection of brain-stem. Ventral view. File:Gray691.png, Dissection of brain-stem. Dorsal view. File:Slide5gg.JPG, External capsule File:Slide7kk.JPG, External capsule File:Slide2GRE.JPG, Ventricles of brain and basal ganglia. Superior view. Horizontal section. Deep dissection. File:Slide3GRE.JPG, Ventricles of brain and basal ganglia.Superior view. Horizontal section. Deep dissection.

References

External links

*
Image at Univ. of South Carolina
Cerebrum {{neuroanatomy-stub