Physiologically, the temporal lobe is an integrator of “sensations, emotions, and behavior” in so far as it relates the organism’s sensory experiences to emotional meaning by its proximity to the limbic system. Similar integrative mechanisms are operative in the parietal lobe, but only in the temporal lobe are they brought into close relationship to one’s instinctive and emotional life. Self-awareness also requires a coherent and sequential stream of thought. Where the inner “stream of thought” (William James’ term for constant thinking) is perceived is still an open question. Given the requirement that it be close to other integrated sensory experiences and that it incorporate the temporal lobe functions of both language and memory, a locus in the temporal lobes seems likely. Some hint of the role of the temporal lobe in our personal and emotional lives was suggested by Hughlings Jackson in the nineteenth century, derived from his insightful analysis of the psychic states accompanying temporal lobe seizures. Later, the observations of Penfield and his collaborators on the effects of stimulating the temporal lobes in the conscious patient undergoing surgical correction of epilepsy revealed something of its complex functions. The seminal writings on this subject include Williams’ chapter on temporal lobe syndromes in the Handbook of Clinical Neurology and the monographs by Penfield and Rasmussen (The Cerebral Cortex of Man) and by Alajouanine and colleagues (Les Grandes Activités du Lobe Temporale).
Clinical Effects of Temporal Lobe Lesions
The symptoms that arise as a consequence of disease of the temporal lobes may be divided into disorders of (1) special senses (visual, auditory, olfactory, and gustatory), (2), language, (3) memory and time perception, (4) emotion, and behavior. Of central importance also are the roles of the superior part of the dominant (usually left) temporal lobe in language and handedness. Several of these functions and their derangements are of such scope and importance that they are accorded separate chapters. Language is discussed in Chap. 22, memory in Chap. 20, and the neurology of emotion and behavior in Chap. 24; these subjects are omitted from further discussion here.
In Chap. 12 (on vision), it was pointed out that lesions of the white matter of the central and posterior parts of the temporal lobe characteristically involve the lower arching fibers of the geniculocalcarine pathway (Meyer loop). This results in an upper homonymous quadrantanopia, usually not perfectly congruent. However, there is considerable variability in the arrangement of visual fibers as they pass around the temporal horn of the lateral ventricle, accounting for the smallness of the field defect in some patients after temporal lobectomy or stroke and extension into the inferior field in others. Quadrantanopia from a dominant (left-sided) lesion is often combined with aphasia.
Bilateral lesions of the temporal lobes render a monkey psychically blind. It can see and pick up objects but does not recognize them until they are explored orally. Natural emotional reactions such as fear are lost. This syndrome, named for Klüver and Bucy, has been identified only in partial form in humans (Lilly et al and Marlowe and colleagues). Using special tests, lesser degrees of visual imperception were uncovered in patients by Milner (1971) and by McFie and colleagues. This syndrome is further discussed in Chap. 24.
Visual hallucinations of complex form, including ones of the patient himself (autoscopy), appear during temporal lobe seizures. Penfield was able to induce what he called “interpretive illusions” (altered impressions of the present) and to reactivate past experiences completely and vividly in association with their original emotions. Temporal lobe abnormalities may also distort visual perception; seen objects may appear too large (macropsia) or small (micropsia), too close or far away, or unreal. Some visual hallucinations have an auditory component: an imaginary figure may speak and move and, at the same time, arouse intense emotion in the patient. The entire experience may seem unnatural and unreal to the patient.