The white matter of the brain consists of a large number of nerve fibers that fill the space between the cerebral cortex and basal nuclei. They spread in different directions and form the pathways of the big hemispheres. Conventionally, nerve fibers are divided into three groups: associative, commissural (transverse), projection.
They implement interconnection between different zones of the cortex, localized in the same hemisphere. Allocate short, which connect with each other adjacent gyrus, and long, connecting distant areas. Short, lying directly under the bark, called subcortical, and located in the deeper layers – intracortical. Long include, for example, the upper and lower longitudinal beams. The upper longitudinal bundle originates in the frontal lobe and penetrates through the occipital into the temporal lobe. Lower combines the temporal and occipital lobes. In addition, a hooked tuft is located between the temporal and frontal lobes. Another formation – this belt, is a fiber in the lumbar gyrus, the function of which is to connect the podmosolic body and hook.
Part of the brain commissures (adhesions), connecting the symmetrical regions of the hemispheres. Therefore, they have a common transverse direction. Thanks to these fibers, the possibility of combining their functions is realized. They form three adhesions of the large brain, the most massive of which is the corpus callosum. It consists of the largest number of transverse fibers that connect the neocortex with the corresponding zones of the opposite hemisphere. The anterior commissure binds together the two olfactory bulbs and the frontal lobe. The arch is formed by arcuate tufts located between the hippocampus and the mastoid bodies.
Connect the cerebral cortex with the underlying links of the central nervous system. They are united in the semi-oval center (radiant crown), which is immersed in the white matter of the brain. There are afferent (bringing, centripetal) organisms that transmit impulses from organs and tissues to the brain and efferent (outgoing, centrifugal) projection pathways that transmit excitation from the central nervous system.
Between the optic tubercle and the basal nuclei, there is an accumulation of projection fibers in the form of a curved plate of white matter called the inner capsule. It consists of the following sections: front leg, knee, rear leg. Each of the elements of the inner capsule is formed by paths and bundles. For example, the anterior pedicle is formed by the anterior thalamic radiations, which realize the connection between the nuclei of the thalamus and the frontal lobe, and the frontal-bridge path connecting the frontal lobe and the nucleus of the bridge. The knee of the inner capsule serves as the point of contact for both legs. It forms the cortical-nuclear pathway, which in turn is an integral part of the pyramidal path and tends to the nuclei of the cranial nerves. The back leg is represented by the following fibers: cortico-spinal, cortical-red core, cortico-reticular, cortico-talamic, thalamo-temenal, central thalamic radiations connecting the corresponding elements of the brain.
White matter functions of the brain
The white matter of the cerebral hemispheres provides an interconnection between different parts of the nervous system. This allows her to coordinate all the work of our body.
– The white matter of the brain connects the homologous elements of both hemispheres.
– Implements the connection of the visual mound with the zones of the cortex.
– Connects areas of the cerebral cortex with the rest of the nervous system.
-Forms a close relationship between the convolutions within the right and left hemispheres.
Damage to the white matter of the brain
Among the diseases affecting the white matter of the brain, there are limited pathologies of the inner capsule, violations of the hemispheric substances, pathologies of the corpus callosum, mixed syndromes.
– in case of damage to the knee and the front part of the back leg, hemiplegia develops – paralysis of the muscular system of one half of the human body.
– affection of the back of this leg is accompanied by an impaired sensitivity and “three hemi syndrome”: hemianesthesia (loss of pain and temperature sensitivity of half of the face on one side, body and extremities on the opposite), hemianopia (visual field defect) and hemiatxia (violation of proprioceptive sensitivity).
– defects of the white matter of the hemispheres are accompanied by symptoms close to those described above, in addition to this, the full half of the nature of the pathology may occur.
– a lesion of the corpus callosum provokes disorders of the patient’s mental functions. So, for example, agnostics (failure to recognize phenomena and objects), apraxia (lack of purposeful actions) may occur, pseudobulbar symptoms are also typical.
– bilateral foci of damage are manifested by speech and swallowing disorders and pyramidal symptoms.