title: Hippocampal structure predicts cortical indices of reactivation of related items.
abstract: One of the key components of relational memory is the ability to bind together the constituent elements of a memory experience, and this ability is thought to be supported by the hippocampus. Previously we had shown that these relational bindings can be used to reactivate the cortical processors of an absent item in the presence of a relationally bound associate (Walker et al., 2014). Specifically, we recorded the event-related optical signal (EROS) when presenting the scene of a face-scene pair during a preview period immediately preceding a test display, and demonstrated reactivation of a face-processing cortical area (the superior temporal sulcus, STS) for scenes that had been previously paired with faces, relative to scenes that had not. Here we combined the EROS measures during the same preview paradigm with anatomical estimates of hippocampal integrity (structural MRI measures of hippocampal volume and diffusion tensor imaging measures of mean fractional anisotropy and diffusivity) to provide evidence that the hippocampus is mediating this reactivation phenomenon. The study was run in a sample of older adults aged 55-87, taking advantage of the high amount of hippocampal variability present in aging. We replicated the functional reactivation of STS during the preview period, specific to scenes previously paired with faces. Crucially, we also found that this phenomenon is correlated with structural hippocampus integrity. Both STS reactivation and hippocampal structure predicted subsequent recognition performance. These data support the theory that relational memory is sustained by an interaction between hippocampal and cortical sensory processing regions, and that these functions may be at the basis of episodic memory changes in normal aging.
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL, USA. Electronic address: walker45@illinois.edu.
authors.forename: John A
authors.initials: JA
authors.lastname: Walker
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Low
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fletcher
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Neal J
authors.initials: NJ
authors.lastname: Cohen
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Gratton
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Monica
authors.initials: M
authors.lastname: Fabiani
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000502:physiology* / Q000523:psychology; D001245:Association Learning / Q000502:physiology; D056324:Diffusion Tensor Imaging; D005071:Evoked Potentials; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D009929:Organ Size; D010364:Pattern Recognition, Visual / Q000502:physiology*; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000502:physiology*
keywords: Aging; Diffusion tensor imaging; Episodic memory; Hippocampal volume; Memory retrieval; Relational memory