title: Is a novel conceptual unit more than the sum of its parts?: FMRI evidence from an associative recognition memory study.
abstract: Recollection, an effortful process relying on the integrity of a brain network including the hippocampus, is generally required to remember arbitrary associations whereas a simple familiarity signal arising in the perirhinal cortex is sufficient to recognize single items. However, the integration of separate items into a single configuration (unitization) leads to reduced involvement of recollection and greater reliance on familiarity. This seems to imply that unitized associations are processed similar to single items. Here, using functional magnetic resonance imaging, we investigated the effects of unitization as encoding strategy on retrieval processes in a between-group-design. A definition was provided that allows combining two unrelated words into a novel conceptual unit (e.g., milk taxi = a delivery service, which is directly dispatched from a farm). We compared this to an encoding strategy in which the words were studied as parts of a sentence. We included pairs in reversed order at test because reversing a unitized word pair is assumed to disrupt the unit while leaving item familiarity for the single constituents intact. This enabled us to compare recognition memory for novel units and single items. Sentence encoding led to a flexible recruitment of brain areas previously associated with recollection, irrespective of the order of the test pair. Unitization encoding reduced the involvement of the recollection network and specifically engaged regions within the parahippocampal cortex and the medial prefrontal cortex for novel units. In contrast, recognition of reversed pairs involved activation of BA 45 in the left inferior frontal gyrus. This possibly suggests that familiarity for novel units and single items are associated with different brain networks.
authors.affiliation: Experimental Neuropsychology Unit, Department of Psychology, Saarland University, P.O. Box 15 11 50, 66041 Saarbrücken, Germany; Department of Cognitive and Clinical Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159 Mannheim, Germany. Electronic address: regine.bader@zi-mannheim.de.
authors.forename: Regine
authors.initials: R
authors.lastname: Bader
authors.affiliation: School of Psychology, University of Surrey, Guildford GU2 7XH, UK.
authors.forename: Bertram
authors.initials: B
authors.lastname: Opitz
authors.affiliation: Department of Neuroradiology, Saarland University Hospital, Kirrberger Straße, 66421 Homburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Reith
authors.affiliation: Experimental Neuropsychology Unit, Department of Psychology, Saarland University, P.O. Box 15 11 50, 66041 Saarbrücken, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Mecklinger
mesh_terms: D000328:Adult; D001245:Association Learning / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009434:Neural Pathways / Q000502:physiology; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011930:Reaction Time; D011932:Reading; D021641:Recognition, Psychology / Q000502:physiology*; D055815:Young Adult
keywords: Familiarity; Recognition memory; Recollection; Unitisation