An Electrophysiological Study of Thalamo-Hippocampal Relationships
The hippocampus has been the source of much investigation in recent years. Its characteristic gross appearance and considerable size in higher species has stimulated wide interest relative to its function which has resulted in numerous speculations as to its precise role and degree of significance in the nervous system. Although much is known about its efferent connections, about the activity resulting from electrical stimulation of the structure and about functional deprivation following lesions of the hippocampus, incomplete evidence exists concerning the afferent pathways mediating sensory information which arrives there. | It has been said that the hippocampus is affected by the same afferent modalities as the cerebral cortex, though subserving different functions (Green and Arduini, 1954), and hippocampal potentials have been recorded following stimulation peripherally (visual, acoustic, gustatory, somatosensory, and other kinds of stimuli; Ungiadze, 1968), or stimulation of the cortex and of various subcortical structures (MacLean, 1967; Sager and Butkhuzi, 1962; Green and Adey, 1956; Robinson and Lennox, 1951). Evoked potential studies have indicated that afferent connections to the hippocampus are primarily by way of the entorhinal area (Adey et al., 1957) while other evidence suggests indirect sensory pathways mediated by connections from the ascending activating system to the septum with the dorsal fornix completing the relay to the hippocampus (Green and Arduini, 1954) and also by connections from cortical areas via the cingulum to the entorhinal area (White, 1959).
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