The auditory receptive region is located in the transverse temporal gyri (Heschl's convolutions), which lie on the dorsal surface of the posterior part of the superior temporal convolution. The auditory radiations pass from the medial geniculate body to the auditory receptive region. Hearing is bilaterally represented in the temporal lobes, although a greater number of impulses may be received from the contralateral ear.
Stimulation of the superior temporal gyrus produces vague auditory hallucinations in the form of tinnitus and sensations of roaring and buzzing, and stimulation of adjacent areas causes vertigo and a sensation of unsteadiness. Unilateral destruction of the transverse temporal gyri does not cause deafness (because of bilateral representation of hearing). Destruction of Wernicke’s speech area in the dominant hemisphere (posterior part of the superior temporal gyrus) results in a receptive aphasia (Wernicke’s aphasia), in which patient cannot understand any form of language. Speech is spontaneous, fluent, and rapid but makes little sense.
The optic radiations pass through the temporal lobe and curve around the descending horn of the lateral ventricle; lesion of them may cause either a superior quadrantic or hemianopic defect in the visual fields. Destruction of olfactory tract results in ipsilateral anosmia. The stimulation of the temporal lobe cortex in epileptic patients gives rise to illusions of perception, olfactory, visual and gustatory hallucinations, dreamy states and reminiscences and automatisms. Petit mal is a typical symptom of temporal lobe lesion. These phenomena have been found to be associated with abnormal discharges or pathologic lesions of the anterior and medial portions of the temporal lobes, including the hippocampal gyrus, uncus, amygdaloid complex, and hippocampus, or the subcortical connections of these structures, many of which actually belong to the limbic system. Hippocampal cortex (archicortex). Bilateral lesion result in the inability to consolidate short-term memory into long-term memory; earlier memories are retrievable. Olfactory and gustatory hallucinations are results of the uncus irritative lesion.