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The cognitive neuroscience of memoryScott D. Slotnick aa Department of Psychology, Boston College, Chestnut Hill, MA, USA

Version of record first published: 27 Jul 2012

To cite this article: Scott D. Slotnick (2012): The cognitive neuroscience of memory, Cognitive Neuroscience, 3:3-4, 139-141

To link to this article: http://dx.doi.org/10.1080/17588928.2012.696536

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Introduction

The cognitive neuroscience of memory

Scott D. Slotnick

Department of Psychology, Boston College, Chestnut Hill, MA, USA

The cognitive neuroscience of long-term memory is ingrained with the assumptions that a particular task measures asingle cognitive process and that each cognitive process is mediated by a single brain region. However, theseassumptions are simplistic and hindering progress toward understanding the true mechanisms of memory. Thisspecial issue of Cognitive Neuroscience presents five empirical papers and two theoretical discussion papers withpeer commentaries on the spatial and/or temporal mechanisms of memory. Using fMRI, Yu et al. show ventralparietal cortex sub-regions mediate dissociable aspects of recollection, and Mickley Steinmetz et al. study time-delay effects on processes engaged during emotional versus neutral item encoding. Employing ERPs, Galli et al.investigate anticipatory activity and recall, and Evans et al. study the effect of cognitive demands on recollectionactivity. Using fMRI and ERPs, Herzmann et al. investigate spatial-temporal activity associated with recognition.Voss et al. review electrophysiological, fMRI, and behavioral evidence indicating implicit memory can influenceexplicit memory measures. Gotts et al. review electrophysiological, fMRI, and modeling evidence to evaluateproposals of repetition priming and highlight neural synchronization. These papers embrace complex cognitive andneural processes, and thus will provide a framework for future studies to investigate the mechanisms of memory.

Keywords: Explicit memory; Implicit memory; Recollection; Familiarity; Mechanisms; fMRI; ERPs; Review.

Long-term memory refers to the encoding or retrievalof information that is mediated by conscious or non-conscious processing. Perhaps due to the inherent com-plexity of this topic, the cognitive neuroscience ofmemory is fraught with simplifying assumptions. Forinstance, explicit/direct memory tasks (such as old-newrecognition) are widely assumed to measure consciousprocessing, while implicit/indirect memory tasks (suchas repetition priming) are widely assumed to measurenonconscious processing. In addition, the “remember”-“know” task is generally thought to dissect explicitmemory into recollection (measured by “remember”responses) and familiarity (measured by “know”responses). However, the cognitive processes mediat-ing such tasks are not pure. Both conscious and non-conscious processes operate, to some degree, during

explicit and implicit tasks, and recollection and famil-iarity often co-occur.

Cognitive neuroscientists also assume that particu-lar mental processes are associated with specific brainregions. This is illustrated by a few (of the numerous)examples from the field of memory—the hippocampusand the perirhinal cortex have been associated withrecollection and familiarity, respectively, the ventrallateral parietal cortex has also been associated withrecollection, and the prefrontal cortex has been linkedto post-retrieval monitoring. Such process-to-regionmappings are reminiscent of phrenology (Uttal, 2003;for an excellent review of phrenology, a pseudosciencedeveloped by Franz Joseph Gall over two centuriesago, see van Wyhe, 2004). The current modular viewof brain function can be attributed to our overrelianceon functional magnetic resonance imaging (fMRI), a

COGNITIVE NEUROSCIENCE, 2012, 3 (3–4), 139–141

Correspondence should be addressed to: Scott D. Slotnick, Department of Psychology, Boston College, McGuinn Hall, Chestnut Hill, MA02467, USA. E-mail: sd.slotnick@bc.edu

© 2012 Psychology Press, an imprint of the Taylor & Francis Group, an Informa businesswww.psypress.com/cognitiveneuroscience http://dx.doi.org/10.1080/17588928.2012.696536

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method which typically produces a very limited num-ber of brain activations that are assumed to mediate aparticular cognitive process. However, there is no evi-dence for the existence of independent cognitive pro-cessing modules in the brain (the opposite is true—multiple brain regions are known to interact during anycognitive process), and such a static modular viewimplies temporal aspects of processing are unimportant(which is also unequivocally false) (Slotnick, in press).Regarding the latter point, fMRI measures brainactivity in seconds, but the brain operates in millise-conds; therefore, this technique cannot be used in iso-lation to study the spatial-temporal dynamics of thefunctioning brain.

Although adhering to one-to-one task-to-processand process-to-region mappings has historically pro-vided some insight into memorial processing, suchsimplistic assumptions are presently hindering pro-gress toward understanding the true mechanisms ofmemory. The papers in this special issue of CognitiveNeuroscience challenge many assumptions that arecurrently (mis)guiding the large majority of researchon memory.

The first two empirical papers in this special issueuse fMRI to isolate neural activity associated withspecific cognitive processes. Yu, Johnson, and Ruggshow that activity in the angular gyrus varies as afunction of recollection confidence, while activity inthe temporal parietal junction corresponds to recollec-tion independent of confidence. This suggests there aredifferent forms of recollection associated with particu-lar sub-regions of the ventral lateral parietal cortex.Mickley Steinmetz, Schmidt, Zucker, and Kensingerinvestigate the effect of a 0.5 or a 24 hour study-to-testtime delay on the neural processes engaged duringemotional item encoding versus neutral item encoding.They find that for neutral items the correspondence ofencoding activity to subsequent memory performanceis stronger at the short delay than the long delay, but foremotional items the correspondence is at least as strongat the long delay as compared to the short delay. Thisillustrates that varying study-to-test delay can be usedto gain insight into the neural processes mediatingdifferent forms of memory. Of importance, rather thansimply using fMRI to identify regions of activity asso-ciated with popular tasks and presumed underlyingcognitive processes, the two previous fMRI studiesuse more complex experimental protocols to uncovernovel characteristics of memory.

The next three empirical papers in this special issueuse event-related potentials (ERPs) to investigate thetime course of memorial processing. Galli, Choy, andOtten study the relationship between anticipatoryactivity—500 milliseconds before the onset of visual

words or auditory words during elaborative encodingor rote encoding—and subsequent recall. They findthat frontal activity preceding auditory words duringelaborative encoding predicts later recall, which sug-gests semantic anticipatory processes are particularlyimportant for encoding these items. Evans, Herron, andWilding manipulate item spatial location (left visualfield or right visual field) and task (animate/inanimatejudgments or pleasant/unpleasant judgments) duringencoding, and then during retrieval a “location” cueor a “task” cue dictates the appropriate response foreach item. They find that the magnitude of left parietalhit versus correct rejection activity 500–800 millise-conds after onset (i.e., the left parietal old-new recogni-tion effect) is larger for repeated than non-repeatedcues/trials. These results show that cognitive demandscan influence the left parietal old-new recognitioneffect, an index of episodic detail/recollection. It isnotable that the previous ERP findings would havebeen difficult, if not impossible, to track using fMRIdue to the rapid temporal dynamics of these effects.Herzmann, Jin, Cordes, and Curran combine fMRI andERPs in the same participants to investigate spatial-temporal activity associated with object recognition.The ERP memory components they evaluate includefrontal activity that occurs 300–500 milliseconds fol-lowing cue onset (the FN400) thought to reflect famil-iarity, parietal activity that occurs 500–800milliseconds following cue onset thought to reflectrecollection (the left parietal old-new recognition effectmentioned above; Evans et al.), and frontal activity thatoccurs 800 milliseconds or later following cue onsetbelieved to reflect post-retrieval monitoring. This studyevaluates recognition activity separately during fMRIand ERPs and also elucidates the relationships betweenthe results obtained using these two techniques. Byemploying ERPs, the previous three studies investigatethe rapid neural processes that mediate memory.

The two review papers in this issue evaluate awealth of recent evidence and challenge commonlyheld beliefs regarding the cognitive processes mea-sured by explicit memory tasks and the neural mechan-isms underlying priming effects, respectively. Voss,Lucas, and Paller review electrophysiological,fMRI, and behavioral evidence and build a very strongcase that implicit memory can influence measuresthought to reflect the explicit process of familiarity.Specifically, they conclude that the ERP FN400 com-ponent reflects conceptual implicit memory. This posi-tion is in direct opposition to the widely held view thatthe FN400 reflects familiarity (see Herzmann et al., thisissue), which highlights that the nature of this ERPcomponent is currently a hotly debated topic. Ninepeer commentaries on this review paper, with a

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rejoinder by the authors, are also included in this spe-cial issue by the following investigators: (1) HowardEichenbaum, (2) Jason Taylor and Richard Henson, (3)Anne Cleary, (4) Jennifer Ryan, (5) Wei-chun Wangand Andrew Yonelinas, (6) Ilana Dew and RobertoCabeza, (7) Craig Stark, (8) Scott Hayes and MiekeVerfaellie, and (9) Edward Wilding. In the secondreview paper, Gotts, Chow, and Martin review electro-physiological, fMRI, and neural modeling evidence toevaluate four proposals of repetition priming:facilitation, sharpening, enhanced neural synchroniza-tion, and Bayesian “explaining away”. These investi-gators convincingly argue that repetition primingeffects are mediated, to some degree, through enhancedneural synchronization, and outline several experi-ments that should be able to adjudicate between theseproposals of repetition priming. Nine peer commen-taries on this review paper, with a rejoinder by theauthors, are also included in this special issue by thefollowing investigators: (1) Karl Friston, (2) MichaelEwbank and Richard Henson, (3) Richard Henson, (4)Maximilian Riesenhuber, (5) Kevin Weiner andKalanit Grill-Spector, (6) David McMahon, (7) Aidan

Horner, (8) GaganWig, and (9) Ben Dyson and ClaudeAlain.

All of the empirical papers and review papers in thisspecial issue represent the cutting edge of cognitiveneuroscience research and theory on memory. Ratherthan relying on widespread beliefs and simplisticassumptions, these papers embrace complex cognitiveand neural processes to make significant progresstoward understanding the spatial-temporal mechan-isms of memory. As such, this special issue will pro-vide a framework for future studies that aim toinvestigate the true neural mechanisms underlyinglong-term memory.

REFERENCES

Slotnick, S. D. (in press). Controversies in cognitive neu-roscience. Basingstoke, UK: Palgrave Macmillan.

Uttal, W. R. (2003). The new phrenology. Cambridge, MA:MIT Press.

vanWyhe, J. (2004). Phrenology and the origins of Victorianscientific naturalism. Aldershot, UK: Ashgate.

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