Investigating the relationship between implicit and explicit memory: Evidence that masked repetition priming speeds the onset of recollection

Joanne L Park,David I Donaldson

doi:10.1016/j.neuroimage.2016.06.013

Abstract

Memory theories assume that unconscious processes influence conscious remembering, but the exact nature of the relationship between implicit and explicit memory remains an open question. Within the context of episodic recognition tests research typical shows that priming impacts behavioral and neural indices of familiarity. By this account, implicit memory leads to enhanced fluency of processing, which is then attributed to ‘oldness’ in the context of recognition judgments. Recently, however, behavioral and neuroimaging evidence has emerged to suggest that priming can also influence recollection, suggesting that the rate of recollection increases following priming. Here, we examine the relationship between priming and recollection, using Event-Related Potentials (ERPs) to assess changes in the timecourse of processing. Participants studied a series of words, and episodic memory was assessed using a standard item recognition test, but masked repetition priming preceded half of the test cues. Results confirmed that implicit memory was engaged: priming produced robust facilitation of recognition Reaction Times (RTs), with larger effects for studied than unstudied words. Mapping onto the RT data, ERPs recorded during recognition testing over centro-parietal electrodes revealed N400-like priming effects (250–500ms) that were larger in magnitude for studied than unstudied words. More importantly, priming also had a clear impact on explicit memory, as measured by recollection-related left-parietal old/new effects. While old/new effects for unprimed trials were present during the typical 500–800ms latency interval, the old/new effects seen for primed trials were equivalent in magnitude and topography, but onset ~300ms earlier. ERPs reveal that repetition priming speeds the onset of recollection, providing a novel demonstration that unconscious memory processes can have a measureable, functional, influence on conscious remembering.

Highlights

IntroductionWithin long-term memory a fundamental division is drawn between declarative (i.e., conscious or explicit) and non-declarative (i.e., unconscious or implicit) forms of memory (e.g., see Eichenbaum and Cohen, 2001; Tulving, 1985)
Within long-term memory a fundamental division is drawn between declarative and non-declarative forms of memory
We present the findings of an Event-Related Potential (ERP) study of episodic recognition memory in which we manipulated whether test cues received implicit priming

Summary

Introduction

Within long-term memory a fundamental division is drawn between declarative (i.e., conscious or explicit) and non-declarative (i.e., unconscious or implicit) forms of memory (e.g., see Eichenbaum and Cohen, 2001; Tulving, 1985). Despite this division, a central assumption within memory theory is that unconscious memory processes influence and support conscious remembering. We present the findings of an Event-Related Potential (ERP) study of episodic recognition memory in which we manipulated whether test cues received implicit priming. Before outlining our specific experimental design, we first provide a brief overview of the core memory processes

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