Association Fibers

Association fibers, connect the gyri and lobes of the same hemisphere; they are divided into short and long fibers. The shortest fibers, the arcuate fibers (see Arnold's fibers), connect two adjacent gyri and occupy a superficial position in the white matter of the gyrus;

1- fasc. arcuatus; 2- fasc. fronto-central; 3- fasc. fronto-occipital; 4- fasc. parieto-central; 5- librae arcuatus; 6- fasc. occipito-vertical; 7- fasc. longit. inferior; 8- fasc. subcallosus; 9- fimbria; 10- fasc. uncinatus; 11- fornix; 12- cingulum.

deeper lie the fibers connecting more distant gyri and lobes of the hemispheres. The following long association bundles are known: 1) fasciculus longitudinalis inferior (stratum sagittatum externum, inferior longitudinal fasciculus) connects the occipital lobe with the temporal; 2) fasciculus longitudinalis superior (f. arcuatus) connects the frontal lobe with the parietal and partially with the temporal; 3) fasciculus longitudinalis medialis (syn. fasciculus subcallosus, fasciculus fronto-occipitalis) connects partially the frontal lobe with the occipital, as well as with the gyri of the inner surface; 4) fasciculus uncinatus (uncinate fasciculus) connects the inferior surfaces of the frontal lobe with the temporal; 5) cingulum (fornix periphericus) connects the gyrus fornicatus with the gyri of the inner surface; 6) fasciculus fronto-occipitalis connects the frontal lobe with the occipital; 7) capsula externa connects the claustrum and the cortex of Reil's insula; 8) tapetum. (For details, see the respective bundles.) Less long association fibers connect adjacent lobes: fasciculus fronto-centralis, parieto-centralis, parieto-temporalis, occipito-verticalis, transversus cunei, transversus lingualis. To the association fibers belong the intracortical association fibers of Meynert, lying in the deep parts of the polymorphic layer.