Browsing by Author "Hirschman, Glynne Hilton"

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    The hippocampus and its electrographic activity
    (1983) Hirschman, Glynne Hilton; Du Preez, Peter
    The thesis is divided into two parts. The first part presents a theoretical investigation of the functions of the hippocampus. Three theories are critically examined : (i) the Douglas ( 196 71 1972) and Kimble (1968) proposal that the hippocampus forms the neural substrate of Pavlovian internal inhibition (hereafter referred to as the inhibitory theory); (ii) the Olton, Becker & Handelmann (1979) suggestion that the hippocampus serves as a "working memory" register; and (iii) the O'Keefe & Nadel (1978) hypothesis that the hippocampus functions as a cognitive map. The adequacy of the three theories is tested against anatomical, physiological and behavioural evidence, and it is concluded that only the inhibitory theory is both internally consistent and able to accommodate the data. Furthermore, a detailed evaluation of criticisms of the theory (as presented primarily by Nadel, O'Keefe and Black 1975) reveals that many of the apparent anomalies in. the literature are, in fact, consistent with the theory, while others are based on unsound data. ,Further consideration of the anatomical and behavioural evidence suggests that the hippocampus gives rise to two separate circuits: a dorsal circuit, subserving the functions of internal inhibition, and a ventral circuit, mediating external inhibition. It is posited that the latter circuit produces its disinhibitory effect via the mammillothalamic tract.