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Front. Hum. Neurosci. | doi: 10.3389/fnhum.2018.00258

Single-trial EEG analysis predicts memory retrieval and reveals source-dependent differences

  • 1Electrical and Computer Engineering, University of California, San Diego, United States
  • 2Psychology and Neuroscience, University of Colorado Boulder, United States
  • 3Cognitive Science, University of California, San Diego, United States

We used pattern classifiers to extract features related to recognition memory retrieval from the temporal information in single-trial EEG data during attempted memory retrieval. Two-class classification was conducted on correctly remembered trials with accurate context (or source) judgments vs. correctly rejected trials. The average accuracy for datasets recorded in a single session was 61% while the average accuracy for datasets recorded in two separate sessions was 56%.  To further understand the basis of the classifier’s performance, two other pattern classifiers were trained on different pairs of behavioral conditions. The first of these was designed to use information related to remembering the item and the second to use information related to remembering the contextual information (or source) about the item. Mollison and Curran (2012) had earlier showed that subject’s familiarity judgements contributed to improved memory of spatial contextual information but not of extrinsic associated color information.These behavioral results were similarly reflected in the event-related potential (ERP) known as the FN400 (an early frontal effect relating to familiarity) which revealed differences between correct and incorrect context memories in the spatial but not color conditions. In our analyses we show that a classifier designed to distinguish between correct and incorrect context memories, more strongly involves early activity (400-500 ms) over the frontal channels for the location distinctions, than for the extrinsic color associations. In contrast, the classifier designed to classify memory for the item (without memory for the context), had more frontal channel involvement for the color associated experiments than for the spatial experiments. Taken together these results argue that location may be bound more tightly with the item than an extrinsic color association. The multivariate classification approach also showed that trial-by-trial variation in EEG corresponding to these ERP components were predictive of subject’s behavioral responses. Additionally, the multivariate classification approach enabled analysis of error conditions that did not have sufficient trials for standard ERP analyses. These results suggested that false alarms were primarily attributable to item memory (as opposed to memory of associated context), as commonly predicted, but with little previous corroborating EEG evidence.

Keywords: EEG, memory retrieval, Old/new effect, Multi-variate analysis, prediction, single-trial analysis

Received: 11 Sep 2017; Accepted: 05 Jun 2018.

Edited by:

Felix Putze, University of Bremen, Germany

Reviewed by:

Dezhong Yao, University of Electronic Science and Technology of China, China
Jing Jin, East China University of Science and Technology, China
Marco Steinhauser, Catholic University of Eichstätt-Ingolstadt, Germany  

Copyright: © 2018 Noh, Liao, Mollison, Curran and De Sa. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Virginia R. De Sa, University of California, San Diego, Cognitive Science, 9500 Gilman Dr, 0515, La Jolla, San Diego, 92093-0515, California, United States, desa@cogsci.ucsd.edu