projection fibers


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projection fibers

[prə′jek·shən ‚fī·bərz]
(anatomy)
Fibers joining the cerebral cortex to lower centers of the brain, and vice versa.
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References in periodicals archive ?
The white fiber tracts in the brain are divided into three groups: association fibers that connect different cortical regions within the same hemisphere as the U-shape fibers, or arched fibers; commissural fibers that are responsible for the connection of the two hemispheres, for instance, the corpus callosum and the anterior commissure; and finally, projection fibers that establish connection between cortical and other CNS structures at different levels, such as the basal ganglia, brain stem and spinal cord, as well as other distant cortical regions (4).
In this sense, the optical radiation can be considered as projection fibers, which leads visual information from the thalamus (lateral geniculate body) to the occipital cortex around the calcarine sulci.
Cerebrum includes in its composition, the cerebral cortex (with a thickness between 2mm and 4mm), which is composed of gray matter (composed of local networks of neurons with dendrites and short unmyelinated axons), being located on the surface and covering the white matter (composed of very long myelinated axons which realize global and rapid nervous communication; it contains association fibers, which conduct nerve impulses between neurons corresponding to the same cerebral hemispheres-commissural fibers that connect neurons and gyri, between hemispheres and projection fibers which forms ascending and descending tracts necessary for the transmission of nerve impulses from the cerebrum into the other parts of the brain and/or spinal cord and vice versa).