title: Active hippocampus during nonconscious memories.
abstract: The hippocampal formation is known for its importance in conscious, declarative memory. Here, we report neuroimaging evidence in humans for an additional role of the hippocampal formation in nonconscious memory. We maskedly presented combinations of faces and written professions such that subjects were not aware of them. Nevertheless, the masked presentations activated many of the brain regions that unmasked presentations of these stimuli did. To induce a nonconscious retrieval of the faces and face-associated occupational information, subjects were instructed to view the previously masked faces and to guess the professional category of each person--academic, artist, and workman. Guessing the professional category of previously masked versus new faces activated the left and right hippocampal formation and right perirhinal cortex as well as bilateral fusiform areas and fronto-temporal areas known to mediate the retrieval of semantic information. These activations within the semantic processing system suggest that conceptual knowledge acquired during masking was nonconsciously retrieved. Our data provide clues to an analogous role of the hippocampus in conscious and nonconscious memory.
authors.affiliation: Division of Psychiatry Research, Psychiatric University Hospital, University of Zürich, Lenggstrasse 31, 8029 Zürich, Switzerland. Henke@bli.unizh.ch
authors.forename: Katharina
authors.initials: K
authors.lastname: Henke
authors.forename: Valerie
authors.initials: V
authors.lastname: Treyer
authors.forename: Eva Turi
authors.initials: ET
authors.lastname: Nagy
authors.forename: Stefan
authors.initials: S
authors.lastname: Kneifel
authors.forename: Max
authors.initials: M
authors.lastname: Dürsteler
authors.forename: Roger M
authors.initials: RM
authors.lastname: Nitsch
authors.forename: Alfred
authors.initials: A
authors.lastname: Buck
mesh_terms: D000328:Adult; D003243:Consciousness / Q000502:physiology*; D005145:Face; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D007092:Imagination; D008297:Male; D008568:Memory / Q000502:physiology*; D009790:Occupations; D012660:Semantics