External capsule
Encyclopedia
The external capsule is a series of white matter
fiber tracts in the brain
. These fibers run between the most lateral (toward the side of the head) segment of the lentiform nucleus
and the claustrum
.
The external capsule is a route for cholinergic
fibers from the basal forebrain
to the cerebral cortex
.
The external capsule eventually joins the internal capsule around the lenticular nucleus.
White matter
White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
fiber tracts in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. These fibers run between the most lateral (toward the side of the head) segment of the lentiform nucleus
Lentiform nucleus
The lentiform nucleus or lenticular nucleus comprises the putamen and the globus pallidus within the basal ganglia. It is a large, cone-shaped mass of gray matter just lateral to the internal capsule.-Etymology:...
and the claustrum
Claustrum
The claustrum, which is suspected to be present in all mammals, is a fairly thin vertical curved sheet of subcortical gray matter...
.
The external capsule is a route for cholinergic
Cholinergic
The word choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation. Found in most animal tissues, choline is a primary component of the neurotransmitter acetylcholine and functions with inositol as a basic constituent of lecithin...
fibers from the basal forebrain
Basal forebrain
The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...
to the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
.
The external capsule eventually joins the internal capsule around the lenticular nucleus.