radiation (ra-de-a's hun). i

Divergence in raylike lines from a central point (said especially of light and heat). 2. Any structure presenting the appearance of radiating lines, auditory r. A bundle of fibers in the posterior part of the internal capsule constituting the final neurons in the auditory path. They arise from the thalamus and posterior corpora quadrigemina to terminate in the temporal lobe, superior gyrus, optical r's, optic r. A bundle of nerve fibers in the posterior part of the internal capsule. They constitute the secondary neurons of the optic path. They are derived from the external geniculate bodies, the anterior corpora quadrigemina, and the thalamus (pulvinar), and radiate into the occipital lobes, thalamic r's. Of Spitzka, certain tracts of fibers which radiate into the hemisphere from the optic thalamus. [Lat., radiatio.l