HIPPOCAMPAL FUNCTION AND RELATIONAL PROCESSING

Memory performance following callosotomy suggests that in normal subjects the hippocampus actively integrates information across the hemispheres (Phelps et al. in press). The present interpretation of hippocampal function from studies on humans with hippocampal lesions suggests that the hippocampus is involved in explicit access to declarative information (Squire & Zola-Morgan 1991). While this description may adequately describe the behavioral outcome of hippocampal lesions in humans, the work on split brain patients implies that the underlying processing of the hippocampus does more than allow conscious access to information. In the present chapter we propose that the hippocampus is necessary for forming relations between multiple cues. We present research from rats, monkeys and humans suggesting this to be the case and point out the similarities in the current theories of “relational” (Eichenbaum et al. 1990) or “configural” (Sutherland & Rudy 1989) processing in animals and “cohering” (Hirst 1988) processing in human amnesia. Finally, we discuss how this approach to hippocampal functioning may account for the behavioral consequences of disconnecting or lesioning the hippocampus in humans and hypothesize as to what mnemonic processes may be unique to humans.