ERP Correlates of Encoding Success and Encoding Selectivity in Attention Switching.

Franziska R Richter,Nick Yeung,Glenn R Wylie

doi:10.1371/journal.pone.0167396

Abstract

Long-term memory encoding depends critically on effective processing of incoming information. The degree to which participants engage in effective encoding can be indexed in electroencephalographic (EEG) data by studying event-related potential (ERP) subsequent memory effects. The current study investigated ERP correlates of memory success operationalised with two different measures—memory selectivity and global memory—to assess whether previously observed ERP subsequent memory effects reflect focused encoding of task-relevant information (memory selectivity), general encoding success (global memory), or both. Building on previous work, the present study combined an attention switching paradigm—in which participants were presented with compound object-word stimuli and switched between attending to the object or the word across trials—with a later recognition memory test for those stimuli, while recording their EEG. Our results provided clear evidence that subsequent memory effects resulted from selective attentional focusing and effective top-down control (memory selectivity) in contrast to more general encoding success effects (global memory). Further analyses addressed the question of whether successful encoding depended on similar control mechanisms to those involved in attention switching. Interestingly, differences in the ERP correlates of attention switching and successful encoding, particularly during the poststimulus period, indicated that variability in encoding success occurred independently of prestimulus demands for top-down cognitive control. These results suggest that while effects of selective attention and selective encoding co-occur behaviourally their ERP correlates are at least partly dissociable.

Highlights

A founding observation in research on human memory is that successful encoding depends on establishing an effective cognitive ‘set’ for processing incoming information: Memory will improve to the extent that presented information is attended [1], organised [2], and processed deeply [3], ideally in a manner that relates meaningfully to the way information will be retrieved later [4]
Differences in the event-related potential (ERP) correlates of attention switching and successful encoding, during the poststimulus period, indicated that variability in encoding success occurred independently of prestimulus demands for top-down cognitive control
There was no reliable interaction between Mode and Switch in the reaction time (RT) data, F < 1, and no significant effects at all were found in the error rates, all Fs < 1, with error rates overall being low relative to our previous study [21] in which a shorter cue-stimulus interval (CSI) was used, and participants switched both the semantic task and the material attended

Summary

Introduction

A founding observation in research on human memory is that successful encoding depends on establishing an effective cognitive ‘set’ for processing incoming information: Memory will improve to the extent that presented information is attended [1], organised [2], and processed deeply [3], ideally in a manner that relates meaningfully to the way information will be retrieved later [4]. The second question is whether successful encoding depends on similar mechanisms of top-down cognitive control to those underpinning successful attention switching or task switching [8,9], which would indicate shared cognitive mechanisms (cf [10]). To address these questions, we combined an attention switching design—in which participants saw compound object-word stimuli on each trial, and switched between attending to the object or the word across trials—with a later recognition memory test for those stimuli. The attention-switching phase serves as an incidental encoding task, giving a manipulation of how attention is allocated during encoding

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