Memory and consciousness

Abstract

How exactly conscious and unconscious memory are defined and characterized, and how these types of memory are supported by the brain have been topics of active debate and investigation for decades. Based primarily on early neuropsychological work, several theoretical perspectives have focused on a selective role for the medial temporal lobe (MTL) in conscious memory. However, research outcomes have increasingly tipped the scales against these claims, indicating that structures in the MTL, including the hippocampus, also support unconscious memory, especially when task performance requires processing of associative, spatial, or temporal relationships amongst presented items. Following descriptions of conscious and unconscious memory, including some common pitfalls or misconceptions that plague the discussion and use of these terms, comparisons are made between theoretical perspectives that have focused on how these types of memory are instantiated in the brain. Examples of empirical studies that provide evidence against claims for selective MTL contributions to conscious memory are then reviewed and the potential practical utility of hippocampus-supported unconscious memory is considered. We conclude with some discussion of recent ideas about what might lead to the conscious experience of remembering and to the phenomenological sense of mental time travel (i.e., autonoetic consciousness) that is characteristic of episodic memory.