Human hippocampal‐dependent tasks: Is awareness necessary or sufficient?

Abstract

The hippocampus has been shown to be required for the acquisition of declarative or explicit memory. Whether all hippocampal‐dependent forms of learning and memory are explicit is an open question. Controversy has emerged about the existence of implicit hippocampal‐dependent tasks. Two implicit tasks that may involve the hippocampusare a relational eye tracking task (Ryan et al. (2000) Psychol Sci 11:454–461) and transitive inference (Greene et al. (2006) J Cognit Neurosci 18:1156–1173; Greene et al. (2001) Mem Cognit 29:893–902). Recently, it was shown that both of these tasks may depend upon task awareness (Smith et al. (2006) J Neurosci 26:11304–11312; Smith and Squire (2005) J Neurosci 25:10138–10146). It is argued that in both cases, distinct, explicit versions of the tasks were created, which do not disprove the implicit nature of the original tasks.