December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Distinct brain mechanisms of remembering individual events and their relationships
Author Affiliations & Notes
  • Yoko Higuchi
    Center for Brain Science, RIKEN
  • Ethan Oblak
    Center for Brain Science, RIKEN
  • Kazuhisa Shibata
    Center for Brain Science, RIKEN
  • Footnotes
    Acknowledgements  This work is supported by JSPS Grant Number 20J01411 and 20K14272 to YH, 19H01041, 20H05715, and JST Moonshot R&D JPMJMS2013 to KS.
Journal of Vision December 2022, Vol.22, 3210. doi:
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      Yoko Higuchi, Ethan Oblak, Kazuhisa Shibata; Distinct brain mechanisms of remembering individual events and their relationships. Journal of Vision 2022;22(14):3210.

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      © ARVO (1962-2015); The Authors (2016-present)

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When we remember events, we also form memories relating them to other events. However, how memories of these events and their relationships are processed in the brain remains poorly understood. Based on behavioral and functional magnetic resonance imaging (fMRI) experiments, we report that two different types of processing evolve over time in different brain areas. In a series of experiments, memories were assessed using a visual statistical learning paradigm. During the incidental encoding stage, participants were exposed to a stream of objects while performing a cover task. Unbeknownst to the participants, particular sequences of objects (e.g., ABC) were repeatedly presented. In the test stage, we conducted a surprise memory test to evaluate incidental memories of the exposed sequences. Our preliminary experiment confirmed findings of previous studies; participants acquired memories not only of the actual forward sequences, but also reversed sequences (e.g., CBA) that had never occurred during the encoding stage. In the main experiments, we tested whether participants were able to identify the memorized sequences from non-exposed sequences (memory identification) and to discriminate the forward and reverse sequences (memory discrimination) immediately after and one day after the encoding stage. We found significant decline in memory discrimination one day after the encoding stage while memory identification remained intact (Experiment 1). These results were replicated (Experiment 2), found to be time-dependent, rather than sleep-dependent (Experiment 3), and cannot be explained by mere forgetting of temporal order of the sequences due to the passage of time (Experiment 4). Using fMRI, we found that decreased memory discrimination was associated with activations in the right hippocampus (Experiment 5) while intact memory identification was associated with activations in the left hippocampus (Experiment 6). Our findings suggest that identification of individual memories and discrimination of these memories are subserved by different brain processing, rather than by one.


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