Neural Mechanisms Of Sensory Discrimination

A detailed report of research on localization of sound in space after transection of auditory pathways in the tectum is given. The ability to localize sound in space was measured in a series of patients who had parts of the temporal lobe removed unilaterally and in patients with removal of cortex of the frontal lobes. One patient, had a right hemispherectomy. Three of the patients with temporal lobe ablation made poorer scores than normal subjects or patients with frontal lobe damage. The others made scores as good as some normal subjects. The patient with right hemispherectomy localized a noise source with surprising accuracy, an average error (for light spot placed at estimated source of sound) of about 5 degrees. There was some tendency for localization to be poorer in the auditory field opposite the side of lesion. An attempt was made to discover the areas of association cortex of the temporal lobes that are involved in learning auditory and visual discriminations. In the cat, isolation of auditory areas AI, AII, and Ep from insular-temporal and from other cortex by ablating a band of insular-temporal and from other cortex by ablating a band of surrounding cortical tissue does not affect pattern discrimination. There is no temporary amnesia for the learned habit. In the monkey, new experiments confirmed the finding of earlier experiments that auditory pattern discrimination is impaired but can be relearned after bilateral removal of the anterior part of the superior surface of the superior temporal convolution, a region of cortex that receives projection from the dorsal posterior portion of the lateral geniculate body. (Author).