BY PROF. SAEED ABUEL MAKAREM WHIT MATTER OF THE CERBRUM BY PROF. SAEED ABUEL MAKAREM

White matter of Cerebrum Each cerebral hemisphere consists of: 1- Cerebral cortex: (outer layer of grey matter). 2- White matter: (enormous mass of nerve fibers). 3- Basal ganglia: (collection of grey matter in the white matter). 4- Lateral ventricle: The cavity of the hemisphere.

WHITE MATTER OF CEREBRAL HEMISPHERE There are 3 types: 1- Association fibers: Interconnect cortical sites lying within one hemisphere. They are short or long fibers . 2- Commissural fibers: Connecting functionally related gyri on both hemisphere. 3- Projection fibers: Connecting the cortex with the lower centers in thalamus brain stem, or spinal cord. They are ascending or descending. WHITE MATTER OF CEREBRAL HEMISPHERE

Association fibers Example: 1-Superior longitudinal fasciculus: A- Short association fibers: Connect nearer gyri on the same hemisphere. B- Long association fibers: Connect distant gyri on the same hemisphere. Example: 1-Superior longitudinal fasciculus: Association fibers

Association fibers Example: 1-Superior longitudinal fasciculus: Connects the frontal & occipital lobes. It lies above the insula. It has a subsidiary bundle known as arcuate fasciculus, which connects the frontal & temporal lobes. It is important for language function Association fibers

Association fibers 2- Inferior longitudinal fasciculus: Connects the occipital & temporal poles. It is contributed in visual recognition. 3- Uncinate fasciculus: U-shaped curved around the bottom of the lateral sulcus. It connects the anterior & inferior parts of the frontal gyrus with the temporal gyri. It is important for behavioral regulation. Association fibers

Association fibers 4- Cingulum: Begins in the anterior perforated substance in the frontal lobe. Runs in cingulate gyrus. Curves inferiorly to run in the Parahippocampal gyrus. It is a part of the limbic system It terminates in the Uncus, (smell center).

COMMISSURAL FIBERS The major commissural fibers are: 1-Corps callosum. 2-Anterior commissure. 3-Hippocampal commissure ( Commissure of the fornix).

CORPUS CALLOSUM The greatest commissure of brain. It connects homologous areas of the 2 cereral hemispheres Formed of 4 parts: Rostrum, genu, body & splenium. Lies in floor of great longitudinal fissure . Its inferior surface is attached to fornix by the septum pellucidum. CORPUS CALLOSUM

CORPUS CALLOSUM Rostrum & genu interconnect the anterior part of the frontal lobe. The trunk interconnects the posterior part of the frontal & parietal & temporal lobes. The splenium interconnects the occipital lobes. The fibers of the rostrum & genu arch forward to form forceps minor. The fibers of splenium arch backward to form forceps major.

ANTERIOR COMISSURE Rounded commissure. Lies behind the lamina terminals. Runs transversely in front of the anterior column of fornix. Interconnects the middle & inferior temporal gyri. Also, it connects the olfactory regions of the 2 hemisphere.

HIPPOCAMPAL COMMISSURE Composed of transverse fibers . Interconnects the posterior columns of the fornix.

These are fibers which connect the cortex to other areas in the brain stem & the spinal cord. Projection fibers are 2 types: A- Ascending (afferent),or corticopetal: Conveying fibers to the cortex 1- Thalamic radiation: connecting different thalamic nuclei with different parts of cortex. 2- Optic radiation. 3- Auditory radiation. PROJECTION FIBERS

PROJECTION FIBERS 1. Pyramidal: 2. Corticopontine. B- Descending (Efferent), or corticofugal: 1. Pyramidal: a. Corticospinal. b. Corticobulbar. 2. Corticopontine. 3. Corticoreticular. 4. Corticorubral

INTERNAL CAPSULE Thick band of projection fibers, (porta cerebri). V-shaped with its concavity directed laterally in horizontal section Its concavity is related to Lentiform nucleus. It is formed of: Anterior limb. Genu. Posterior limb.

INTERNAL CAPSULE Anterior limb: It contains: Between head of caudate nucleus & lentiform nucleus. It contains: 1-Anterior thalamic radiation: From anterior & mediodorsal thalamic nuclei, to the frontal cortex. 2-Frontopontine fibers: That project to pontine nuclei, in the basal part of the Pons.

INTERNAL CAPSULE Genu of internal capsule: Is the angle of the V which points medially, between head of caudate nucleus and thalamus. It contains: 1- Corticonuclear (Corticobulbar). 2- Anterior part of sensory (superior thalamic) radiation, from ventral anterior & ventral lateral nuclei to motor regions of the frontal lobe.

INTERNAL CAPSULE Posterior limb: A-Lenticothalamic part Lies between thalamus & lentiform nucleus. Contains: 1-Corticospinal fibers. 2-Frontopontine. 3-Frontorubral. 4-Great part of sensory (superior thalamic ) radiation, from the ventral posterior nucleus to the primary somatosensory cortex.

INTERNAL CAPSULE B-Retrolentiular part: It contains fibers from medial & lateral geniculate nuclei of thalamus, which form the auditory & optic radiation. Optic radiation passes to visual cortex, around the calcarine sulcus (geniculoalcarine fibers). Auditory radiation passes to superior temporal gyrus.