Hippocampus Is Place of Interaction between Unconscious and Conscious Memories.

Züst, Marc Alain; Colella, Patrizio; Reber, Thomas; Vuilleumier, Patrik; Hauf, Martinus; Ruch, Simon; Henke, Katharina (2015). Hippocampus Is Place of Interaction between Unconscious and Conscious Memories. PLoS ONE, 10(3), e0122459. Public Library of Science 10.1371/journal.pone.0122459

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Recent evidence suggests that humans can form and later retrieve new semantic relations unconsciously by way of hippocampus-the key structure also recruited for conscious relational (episodic) memory. If the hippocampus subserves both conscious and unconscious relational encoding/retrieval, one would expect the hippocampus to be place of unconscious-conscious interactions during memory retrieval. We tested this hypothesis in an fMRI experiment probing the interaction between the unconscious and conscious retrieval of face-associated information. For the establishment of unconscious relational memories, we presented subliminal (masked) combinations of unfamiliar faces and written occupations ("actor" or "politician"). At test, we presented the former subliminal faces, but now supraliminally, as cues for the reactivation of the unconsciously associated occupations. We hypothesized that unconscious reactivation of the associated occupation-actor or politician-would facilitate or inhibit the subsequent conscious retrieval of a celebrity's occupation, which was also actor or politician. Depending on whether the reactivated unconscious occupation was congruent or incongruent to the celebrity's occupation, we expected either quicker or delayed conscious retrieval process. Conscious retrieval was quicker in the congruent relative to a neutral baseline condition but not delayed in the incongruent condition. fMRI data collected during subliminal face-occupation encoding confirmed previous evidence that the hippocampus was interacting with neocortical storage sites of semantic knowledge to support relational encoding. fMRI data collected at test revealed that the facilitated conscious retrieval was paralleled by deactivations in the hippocampus and neocortical storage sites of semantic knowledge. We assume that the unconscious reactivation has pre-activated overlapping relational representations in the hippocampus reducing the neural effort for conscious retrieval. This finding supports the notion of synergistic interactions between conscious and unconscious relational memories in a common, cohesive hippocampal-neocortical memory space.

Item Type: Journal Article (Original Article)
Division/Institute: 07 Faculty of Human Sciences > Institute of Psychology > Experimental Psychology and Neuropsychology
10 Strategic Research Centers > Center for Cognition, Learning and Memory (CCLM)
04 Faculty of Medicine > Department of Radiology, Neuroradiology and Nuclear Medicine (DRNN) > Institute of Diagnostic and Interventional Neuroradiology
Graduate School: Swiss Graduate School for Cognition, Learning and Memory (SGS-CLM)
UniBE Contributor: Züst, Marc; Reber, Thomas; Hauf, Martinus; Ruch, Simon and Henke, Katharina
Subjects: 100 Philosophy > 150 Psychology
600 Technology > 610 Medicine & health
ISSN: 1932-6203
Publisher: Public Library of Science
Language: English
Submitter: Martin Zbinden
Date Deposited: 07 Apr 2015 15:20
Last Modified: 14 Jan 2016 12:49
Publisher DOI: 10.1371/journal.pone.0122459
PubMed ID: 25826338
BORIS DOI: 10.7892/boris.67538
URI: http://boris.unibe.ch/id/eprint/67538

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