part of each cerebral hemisphere of the brain. It carries information past the
part of each cerebral hemisphere of the brain. It carries information past the

basal ganglia, separating the caudate nucleus and the thalamus from the
basal ganglia, separating the caudate nucleus and the thalamus from the

putamen and the globus pallidus. The internal capsule contains both ascending
putamen and the globus pallidus. The internal capsule contains both ascending

and descending axons. The internal capsule contains fibres going to and
and descending axons. The internal capsule contains fibres going to and

coming from the cerebral cortex. The corticospinal tract constitutes a
coming from the cerebral cortex. The corticospinal tract constitutes a

large part of the internal capsule, carrying motor information from the
large part of the internal capsule, carrying motor information from the

primary motor cortex to the lower motor neurons in the spinal cord. Above the
primary motor cortex to the lower motor neurons in the spinal cord. Above the

basal ganglia the corticospinal tract is a part of the corona radiata, below the
basal ganglia the corticospinal tract is a part of the corona radiata, below the

basal ganglia the tract is called crus cerebri and below the pons it is
basal ganglia the tract is called crus cerebri and below the pons it is

referred to as the corticospinal tract. Structure
referred to as the corticospinal tract. Structure

The internal capsule is V-shaped when cut horizontally, in a transverse plane.
The internal capsule is V-shaped when cut horizontally, in a transverse plane.

When cut horizontally: the bend in the V is called the genu
When cut horizontally: the bend in the V is called the genu

the anterior limb or crus anterius is the part in front of the genu, between
the anterior limb or crus anterius is the part in front of the genu, between

the head of the caudate nucleus and the lenticular nucleus
the head of the caudate nucleus and the lenticular nucleus

the posterior limb or crus posterius is the part behind the genu, between the
the posterior limb or crus posterius is the part behind the genu, between the

thalamus and lenticular nucleus the retrolenticular portion is caudal to
thalamus and lenticular nucleus the retrolenticular portion is caudal to

the lenticular nucleus and carries the optic radiation also known as the
the lenticular nucleus and carries the optic radiation also known as the

geniculocalcarine tract the sublenticular portion is beneath the
geniculocalcarine tract the sublenticular portion is beneath the

lenticular nucleus and are tracts involved in the auditory pathway from
lenticular nucleus and are tracts involved in the auditory pathway from

the medial geniculate nucleus to the primary auditory cortex
the medial geniculate nucleus to the primary auditory cortex

= Genu = The genu is the flexure of the internal
= Genu = The genu is the flexure of the internal

capsule. It is formed by fibers from the corticonuclear tracts. The fibers in
capsule. It is formed by fibers from the corticonuclear tracts. The fibers in

this region are named the geniculate fibers; they originate in the motor part
this region are named the geniculate fibers; they originate in the motor part

of the cerebral cortex and, after passing downward through the base of the
of the cerebral cortex and, after passing downward through the base of the

cerebral peduncle with the cerebrospinal fibers, undergo decussation and end in
cerebral peduncle with the cerebrospinal fibers, undergo decussation and end in

the motor nuclei of the cranial nerves of the opposite side. It contains the
the motor nuclei of the cranial nerves of the opposite side. It contains the

Corticobulbar tract. = Anterior limb =
Corticobulbar tract. = Anterior limb =

The anterior limb of internal capsule contains:
The anterior limb of internal capsule contains:

fibers running from the thalamus to the frontal lobe;
fibers running from the thalamus to the frontal lobe;

fibers connecting the lentiform and caudate nuclei;
fibers connecting the lentiform and caudate nuclei;

fibers connecting the cortex with the corpus striatum; and
fibers connecting the cortex with the corpus striatum; and

fibers passing from the frontal lobe through the medial fifth of the base of
fibers passing from the frontal lobe through the medial fifth of the base of

the cerebral peduncle to the nuclei pontis.
the cerebral peduncle to the nuclei pontis.

= Posterior limb = The posterior limb of internal capsule
= Posterior limb = The posterior limb of internal capsule

is the portion of the internal capsule posterior to the genu.
is the portion of the internal capsule posterior to the genu.

The anterior two-thirds of the occipital part of the internal capsule contains
The anterior two-thirds of the occipital part of the internal capsule contains

fibers of the corticospinal tract, which arise in the motor area of the cerebral
fibers of the corticospinal tract, which arise in the motor area of the cerebral

cortex and, passing downward through the middle three-fifths of the base of the
cortex and, passing downward through the middle three-fifths of the base of the

cerebral peduncle, are continued into the pyramids of the medulla oblongata.
cerebral peduncle, are continued into the pyramids of the medulla oblongata.

The posterior third of the occipital part contains:
The posterior third of the occipital part contains:

sensory fibers, largely derived from the thalamus, though some may be continued
sensory fibers, largely derived from the thalamus, though some may be continued

upward from the medial lemniscus; the fibers of optic radiation, from the
upward from the medial lemniscus; the fibers of optic radiation, from the

lower visual centers to the cortex of the occipital lobe;
lower visual centers to the cortex of the occipital lobe;

acoustic fibers, from the lateral lemniscus to the temporal lobe; and
acoustic fibers, from the lateral lemniscus to the temporal lobe; and

fibers which pass from the occipital and temporal lobes to the nuclei pontis.
fibers which pass from the occipital and temporal lobes to the nuclei pontis.

= Blood supply = The superior parts of both the anterior
= Blood supply = The superior parts of both the anterior

and posterior limbs and the genu of the internal capsule are supplied by the
and posterior limbs and the genu of the internal capsule are supplied by the

lenticulostriate arteries, which are branches of the M1 segment of the middle
lenticulostriate arteries, which are branches of the M1 segment of the middle

cerebral artery. The inferior half of the anterior limb
cerebral artery. The inferior half of the anterior limb

is supplied via the recurrent artery of Heubner, which is a branch of the
is supplied via the recurrent artery of Heubner, which is a branch of the

anterior cerebral artery. The inferior half of the posterior limb
anterior cerebral artery. The inferior half of the posterior limb

is supplied by the anterior choroidal artery, which is a branch of the
is supplied by the anterior choroidal artery, which is a branch of the

internal carotid artery. In summary, the blood supply of the
internal carotid artery. In summary, the blood supply of the

internal capsule is Anterior limb: lenticulostriate branches
internal capsule is Anterior limb: lenticulostriate branches

of middle cerebral artery and recurrent artery of Heubner off of the anterior
of middle cerebral artery and recurrent artery of Heubner off of the anterior

cerebral artery Genu: lenticulostriate branches of
cerebral artery Genu: lenticulostriate branches of

middle cerebral artery Posterior limb: lenticulostriate
middle cerebral artery Posterior limb: lenticulostriate

branches of middle cerebral artery and anterior choroidal artery branch of the
branches of middle cerebral artery and anterior choroidal artery branch of the

internal carotid artery As in many parts of the body, some
internal carotid artery As in many parts of the body, some

degree of variation in the blood supply exists. For example, thalamoperforator
degree of variation in the blood supply exists. For example, thalamoperforator

arteries, which are branches of the basilar artery, occasionally supply the
arteries, which are branches of the basilar artery, occasionally supply the

inferior half of the posterior limb. Ellis clinical anatomy book says
inferior half of the posterior limb. Ellis clinical anatomy book says

posterior cerebral artery also supply the posterior part of internal capsule
posterior cerebral artery also supply the posterior part of internal capsule

Function Working anterior to posterior:
Function Working anterior to posterior:

The anterior limb of the internal capsule contains:
The anterior limb of the internal capsule contains:

1) Frontopontine fibers project from frontal cortex to pons;
1) Frontopontine fibers project from frontal cortex to pons;

2) Thalamocortical fibers connect the medial and anterior nuclei of the
2) Thalamocortical fibers connect the medial and anterior nuclei of the

thalamus to the frontal lobes. The genu contains corticobulbar fibers,
thalamus to the frontal lobes. The genu contains corticobulbar fibers,

which run between the cortex and the brainstem.
which run between the cortex and the brainstem.

The posterior limb of the internal capsule contains corticospinal fibers,
The posterior limb of the internal capsule contains corticospinal fibers,

sensory fibers from the body and a few corticobulbar fibers.
sensory fibers from the body and a few corticobulbar fibers.

Other fibers within the internal capsule The retrolenticular part contains fibers
Other fibers within the internal capsule The retrolenticular part contains fibers

from the optic system, coming from the lateral geniculate nucleus of the
from the optic system, coming from the lateral geniculate nucleus of the

thalamus. More posteriorly, this becomes the optic radiation. Some fibers from
thalamus. More posteriorly, this becomes the optic radiation. Some fibers from

the medial geniculate nucleus also pass in the retrolenticular internal capsule,
the medial geniculate nucleus also pass in the retrolenticular internal capsule,

but most are in the sublenticular part. The sublenticular part contains fibers
but most are in the sublenticular part. The sublenticular part contains fibers

connecting with the temporal lobe. These include the auditory radiations and
connecting with the temporal lobe. These include the auditory radiations and

temporopontine fibers. Clinical significance
temporopontine fibers. Clinical significance

The lenticulostriate arteries supply a substantial amount of the internal
The lenticulostriate arteries supply a substantial amount of the internal

capsule. These small vessels are particularly vulnerable to narrowing in
capsule. These small vessels are particularly vulnerable to narrowing in

the setting of chronic hypertension and can result in small, punctate
the setting of chronic hypertension and can result in small, punctate

infarctions or intraparenchymal haemorrhage due to vessel rupture.
infarctions or intraparenchymal haemorrhage due to vessel rupture.

Lesions of the genu of the internal capsule affect fibers of the
Lesions of the genu of the internal capsule affect fibers of the

corticobulbar tract. The primary motor cortex sends its axons
corticobulbar tract. The primary motor cortex sends its axons

through the posterior limb of the internal capsule. Lesions, therefore,
through the posterior limb of the internal capsule. Lesions, therefore,

result in a contralateral hemiparesis or hemiplegia. While symptoms of weakness
result in a contralateral hemiparesis or hemiplegia. While symptoms of weakness

due to an isolated lesion of the posterior limb can initially be severe,
due to an isolated lesion of the posterior limb can initially be severe,

recovery of motor function is sometimes possible due to spinal projections of
recovery of motor function is sometimes possible due to spinal projections of

premotor cortical regions that are contained more rostrally in the internal
premotor cortical regions that are contained more rostrally in the internal

capsule. Additional images
capsule. Additional images

References External links
References External links

Stained brain slice images which include the "internal capsule" at the BrainMaps
Stained brain slice images which include the "internal capsule" at the BrainMaps

project hier-180 at NeuroNames
project hier-180 at NeuroNames

Anatomy diagram: 13048.000-2 at Roche Lexicon - illustrated navigator,
Anatomy diagram: 13048.000-2 at Roche Lexicon - illustrated navigator,

Elsevier
Elsevier