Parts
- Think of the origin of the external capsule is the Claustrum and the external capsule fans out from Claustrum
Black line: Dorsal eternal capsule
- Cortical gray matter of the long and short insular gyri and extreme capsule has been removed, exposing the claustrum and external capsule.
- Claustrum 2 parts
- Dorsal (posterosuperior) part,
- Composed of compact gray matter
- sends tracts out via DEC (Dorsal eternal capsule) (aka: CCF (claustral cortical fibres) → cortex between the SMA anteriorly and the parietal lobe posterior
- F(X)
- integration of visual, somatosensory and motor information
- Ventral (anteroinferior) part,
- Composed of islands of gray matter intermixed with and fragmented by fibers of the uncinate and inferior occipitofrontal fasciculi.
- Sends tracts out via VEC (Ventral external capsule) to reach amygdala
- External capsule 2 parts
- Ventral (anteroinferior) part
- composed of the fibers of the uncinate and Inferior occipitofrontal fasciculi
- Deep to the cortex of the limen insulae
- Dorsal (posterosuperior) part: formed by the Claustrocortical fibers
- A group of radiating fibers
- Converge in and merge with the gray matter of the dorsal claustrum,
- forming a characteristic spoke-and-wheel pattern with its center at the dorsal claustrum.
Relations
- Superficial
- Cortical gray matter of the long and short insular gyri followed by extreme capsule
- Deep
- Putamen
Images
DTI imaging: Anterior (green), middle (orange), and posterior (blue), in the region of the insula between the insular cortex and putamen
- Ventral portion (green) is formed by the uncinate and inferior occipitofrontal fasciculi, and
- Dorsal portion has been divided into
- Anterior part of the dorsal portion (orange) is formed by multiple fibers coursing between the superior frontal, precentral, and postcentral gyri and the dorsal claustrum area just above the uncinate and occipitofrontal fasciculi.
- Posterior part of the dorsal portion (blue) is formed by several loops connecting the superior parietal lobule and parieto-occipital region to the dorsal claustrum. The dorsal external capsule contains the claustrocortical system, which has a topographical organization
- Further step in the dissection of the claustrocortical fibers. Removal of the claustrocortical fibers of the dorsal external capsule peels away the gray matter of the dorsal claustrum.
- The fibers from the posterior part of the dorsal external capsule enter the posterior part of the dorsal claustrum
- The fibers coming from the anterior part enter the anterior part of the dorsal claustrum.
- The fibers of the ventral portion of the external capsule belong to the uncinate and inferior occipitofrontal fasciculi, which traverse the most anterior and inferior parts of the claustrum to create the gray matter islands forming the ventral claustrum.
- Tractographic reconstruction of the inferior occipitofrontal fasciculus, which is formed by a group of fibers coming from the prefrontal region and situated dorsal to the frontal fibers of the uncinate fasciculus.
- At the frontotemporal transition zone, the fasciculus narrows in section as it swings around the lower external side of the putamen and continues posteriorly toward the middle and posterior temporal region. It forms part of the ventral portion of the extreme and external capsule
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