One of the four principal lobes of the mammalian BRAIN, located on the lateral aspect. They are apparently named TEMPORAL (from Latin, tempus: time) because this is the part of the head—the temples—on which the passage of time is indicated: one’s hair turns grey here first. It has complex functions including, in humans, SPEECH PRODUCTION and SPEECH PERCEPTION, the understanding of LANGUAGE and MEMORY (see TEMPORAL LOBE AMNESIA for example) have all been associated with the temporal lobe. Sensory functions are also present: the AUDITORY CORTEX is in the upper part of the temporal lobe and olfactory functions are represented in the MEDIAL TEMPORAL LOBE (see OLFACTORY SYSTEM); visual functions are present also (see for example ACHROMATOPSIA). Higher-order associative sensory functions (see for example FACE PERCEPTION) are also represented in the temporal lobe. In humans, its functions show a strong degree of LATERALIZATION.
Clinically, the tem-poral lobe has been associated with AGNOSIA (see also PROSOPAGNOSIA), AMNESIA and with the production of EPILEPSY (TEMPORAL LOBE EPILEPSY), two conditions unfortunately united in patient H.M. who had bilateral LOBECTOMY of the temporal lobes in order to control epilepsy—the operation was successful in controlling the seizures but left H.M. with a permanent amnesic condition.
The anatomy of the temporal lobe is complex, with boundaries between component parts often being indistinct and controversial. At the posterior edge the temporal lobe is bordered by the OCCIPITAL LOBE (more particularly, number 19 of BRODMANN’S AREAS). At the dorsal edge the SYLVIAN FISSURE marks a clear border, though at the point where this ends, the transition from temporal to PARIETAL LOBE is indistinct and defined better by connectivity (principally to the THALAMUS) rather than by gross surface features. The temporal lobe is marked by banks of tissue, with sulci running parallel to the Sylvian fissure. The three main sulci are the superior (at the top) middle and inferior temporal gyri (INFERIOR TEMPORAL GYRUS, MIDDLE TEMPORAL GYRUS and SUPERIOR TEMPORAL GYRUS), with the SUPERIOR TEMPORAL SULCUS and middle temporal sulcus and INFERIOR TEMPORAL CORTEX separated by them. The HIPPOCAMPUS, AMYGDALA and RHINAL SULCUS are embedded in the MEDIAL TEMPORAL LOBE.
