DISORDERS OF THE NERVOUS SYSTEM AND BEHAVIOR
THE NERVOUS SYSTEM clinical state is called Korsakov s syndrome. When due to thiamine deficiency, the most unusual lesions are in the armillary bodies. The hippocampus may be involved in Alzheimer’s disease, head injury, or tumours. Illness of the posterior cerebral artery may cause infarction of the hippocampus.
Herpes simplex encephalitis has a preference for all the structures of the limbic system. Occasional cases of severe memory loss have been reported following bilateral removal of the medial temporal structures surgically. To produce a permanent memory deficit, bilateral lesions of the mammilla-hippocampal system are required.
A patient who shows this disorder let us say a week after the episode may exhibit the following picture. He will be alert, awake, and cooperative and may, on a standard IQ test, score in an average or even superior range besides, his immediate memo-. Or, as shown, for example, by digit span, will be healthy.
By contrast, he shows an intergraded amnesia, i.e., DISORDERS OF THE NERVOUS SYSTEM an inability to learn new material. He also teaches retrograde amnesia extending back from 3 to 20 years. Over the next two or three months, the condition improves. The ability to learn new material reappears (but the patient will have a permanent gap in his memory for the period in which he lacked this ability).
A prominent feature of many but not all cases of Korsakoff s syndrome, especially in the early stages, is confabulation, i.e., the tendency of the patient to invent fanciful replies to questions whose answers he doesn’t know.
e.g., professing total amnesia for all events of his life. Failure of a patient without aphasia to state his- own name is invariably not organic in origin. Although some short-lasting fugue states may occasionally be the result of temporal lobe epilepsy.
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The’ author’s experience has been that these are nearly all functional in origin. Geschwind, N.: Disconnection syndromes in animals and man.Brain, 88:237, 1965.Talland, G. A., and Waugh, N. C.: The Pathology of Memory.
New York, Academic Press, Inc., 1969.Zangwill, 0. L.: Cerebral Dominance and Its Relation to Psychological Function. Springfield, fit, Charles .0 Thomas,1960.