Working memory capacity is related to variations in the magnitude of an electrophysiological marker of recollection

Cue overlap supports preretrieval selection in episodic memory: ERP evidence

People often want to recall events of a particular kind, but this selective remembering is not always possible. We contrasted two candidate mechanisms: the overlap between retrieval cues and stored memory traces, and the ease of recollection. In two preregistered experiments (Ns = 28), we used event-related potentials (ERPs) to quantify selection occurring before retrieval and the goal states — retrieval orientations — thought to achieve this selection. Participants viewed object pictures or heard object names, and one of these sources was designated as targets in each memory test. We manipulated cue overlap by probing memory with visual names (Experiment 1) or line drawings (Experiment 2). Results revealed that regardless of which source was targeted, the left parietal ERP effect indexing recollection was selective when test cues overlapped more with the targeted than non-targeted information, despite consistently better memory for pictures. ERPs for unstudied items also were more positive-going when cue overlap was high, suggesting that engagement of retrieval orientations reflected availability of external cues matching the targeted source. The data support the view that selection can act before recollection if there is sufficient overlap between retrieval cues and targeted versus competing memory traces.

The costs of target prioritization and the external requirements for using a recall-to-reject strategy in memory exclusion tasks: a meta-analysis

In event-related potential (ERP) studies, the left-parietal old/new effect is commonly considered as a neural correlate of recollection. In memory exclusion tasks, the effect is usually observed when the targeted information is identified, but it is not necessarily present when studied items are rejected as nontargets. Interestingly, both the presence and the absence of such old/new effects to nontargets have been regarded as indicator for strategic retrieval. We reviewed previous ERP studies using memory exclusion tasks to analyze the reaction time (RT) pattern in such studies, as well as the influence of task difficulty on the occurrence of nontarget retrieval. We identified 44 test conditions, reported in 24 studies, and subjected the behavioral data to a meta-analysis. The RTs to correctly rejected new items were shorter than the RTs to hits, in particular in studies that required differentiating conceptual or perceptual information at test. When the retrieval of target information was prioritized, RTs to nontargets were delayed relative to targets. Without such prioritization, no such RT differences were observed. For test conditions with nontarget retrieval, the retrieval accuracy was poorer compared with test conditions without such retrieval. The findings support previous studies that claimed that nontarget retrieval becomes more likely when target retrieval is difficult, but the strong overlap in task difficulty between conditions with and without nontarget retrieval indicates that other, partly yet to-be-identified factors contribute to the occurrence of nontarget retrieval as well.

Direct electrophysiological evidence for the maintenance of retrieval orientations and the role of cognitive control

Retrieval orientations are memory states that bias retrieval towards specific memory contents. Many neuroimaging studies have examined the influence of retrieval orientations on stimulus processing, but very little direct evidence exists regarding the ongoing maintenance of orientations themselves. Participants completed two memory tasks with different retrieval goals. ERPs were time-locked to a pre-stimulus fixation asterisk and contrasted according to retrieval goals. Pre-stimulus ERPs elicited during the two retrieval tasks diverged at frontal electrode sites. These differences onset early and were sustained throughout the fixation-stimulus interval. The functional and spatiotemporal characteristics of this ERP effect comprise the first direct electrophysiological evidence of the ongoing maintenance of retrieval orientations throughout a task. Moreover, this effect was eliminated in participants who performed a stroop task prior to the memory tests, indicating that reserves of cognitive control play an important role in the maintenance of retrieval orientations throughout memory tasks.

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Pre-stimulus fixation-locked ERPs differed during recognition according to retrieval goal.

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It is proposed that this preparatory effect is a correlate of retrieval orientation maintenance.

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The preparatory effect was eliminated in participants who first completed a stroop task.

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Cognitive control reserves therefore appear to influence retrieval orientation maintenance.

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Elimination of the preparatory effect was associated with enhanced post-retrieval monitoring.

Investigating the Functional Utility of the Left Parietal ERP Old/New Effect: Brain Activity Predicts within But Not between Participant Variance in Episodic Recollection

A success story within neuroimaging has been the discovery of distinct neural correlates of episodic retrieval, providing insight into the processes that support memory for past life events. Here we focus on one commonly reported neural correlate, the left parietal old/new effect, a positive going modulation seen in event-related potential (ERP) data that is widely considered to index episodic recollection. Substantial evidence links changes in the size of the left parietal effect to changes in remembering, but the precise functional utility of the effect remains unclear. Here, using forced choice recognition of verbal stimuli, we present a novel population level test of the hypothesis that the magnitude of the left parietal effect correlates with memory performance. We recorded ERPs during old/new recognition, source accuracy and Remember/Know/Guess tasks in two large samples of healthy young adults, and successfully replicated existing within participant modulations of the magnitude of the left parietal effect with recollection. Critically, however, both datasets also show that across participants the magnitude of the left parietal effect does not correlate with behavioral measures of memory – including both subjective and objective estimates of recollection. We conclude that in these tasks, and across this healthy young adult population, the generators of the left parietal ERP effect do not index performance as expected. Taken together, these novel findings provide important constraints on the functional interpretation of the left parietal effect, suggesting that between group differences in the magnitude of old/new effects cannot always safely be used to infer differences in recollection.

Aging, working memory capacity and the proactive control of recollection: An event-related potential study

The present study investigated the role of working memory capacity (WMC) in the control of recollection in young and older adults. We used electroencephalographic event-related potentials (ERPs) to examine the effects of age and of individual differences in WMC on the ability to prioritize recollection according to current goals. Targets in a recognition exclusion task were words encoded using two alternative decisions. The left parietal ERP old/new effect was used as an electrophysiological index of recollection, and the selectivity of recollection measured in terms of the difference in its magnitude according to whether recognized items were targets or non-targets. Young adults with higher WMC showed greater recollection selectivity than those with lower WMC, while older adults showed nonselective recollection which did not vary with WMC. The data suggest that aging impairs the ability to engage cognitive control effectively to prioritize what will be recollected.

Retrieval and Monitoring Processes during Visual Working Memory: An ERP Study of the Benefit of Visual Semantics

In this study, we examined electrophysiological indices of episodic remembering whilst participants recalled novel shapes, with and without semantic content, within a visual working memory paradigm. The components of interest were the parietal episodic (PE; 400-800 ms) and late posterior negativity (LPN; 500-900 ms), as these have previously been identified as reliable markers of recollection and post-retrieval monitoring, respectively. Fifteen young adults completed a visual matrix patterns task, assessing memory for low and high semantic visual representations. Matrices with either low semantic or high semantic content (containing familiar visual forms) were briefly presented to participants for study (1500 ms), followed by a retention interval (6000 ms) and finally a same/different recognition phase. The event-related potentials of interest were tracked from the onset of the recognition test stimuli. Analyses revealed equivalent amplitude for the earlier PE effect for the processing of both low and high semantic stimulus types. However, the LPN was more negative-going for the processing of the low semantic stimuli. These data are discussed in terms of relatively 'pure' and complete retrieval of high semantic items, where support can readily be recruited from semantic memory. However, for the low semantic items additional executive resources, as indexed by the LPN, are recruited when memory monitoring and uncertainty exist in order to recall previously studied items more effectively.

Fractionating controlled memory processes and recall of context in recognition memory: a case report

Recollection has been described as both a recognition memory judgment requiring cognitive control and the ability to retrieve contextual information about a prior occurrence. At the core of this article is the question whether or not these two subcomponents of recollection are dissociable in amnesia. In three experiments, we explored the influence of exclusion task instructions on performance in a single case (CJ), with the view to understand the relative contributions of control and source memory to recognition memory decisions. First, contrasting findings were obtained between tasks requiring strategic control or source reports. Second, even though CJ displayed some residual source memory relative to the ability to strategically control this information, his source memory capacity was time-limited. Our findings resonate with the novel proposal that recollection draws heavily upon working memory resources, and provide an example of how amnesic patients might utilize residual working memory capacity to solve episodic memory tasks.

Control over recollection varies with context-type: ERP evidence from the exclusion task

The left-parietal ERP old/new effect—an index of recollection—is often larger for classes of item to-be-endorsed as old (targets) than to-be-rejected items (nontargets), and this has been interpreted as an index of selective retrieval. The question of interest here was whether selective retrieval would be more pronounced when targets are allocated according to distinct conceptual encoding tasks than when designated according to spatial location. Participants saw words on the left/right side of fixation and made a pleasantness or function judgment to each. Across test-blocks, target designation varied according to the kind of task judgment or the study location. Robust target old/new effects were observed for both classes of target designation but the nontarget amplitude was smaller when conceptual information was targeted. The current data indicate that the class of to-be-retrieved information determines the extent to which recollection can be controlled when all other factors are held constant.

Cortical potentials in an auditory oddball task reflect individual differences in working memory capacity

This study determined whether auditory cortical responses associated with mechanisms of attention vary with individual differences in working memory capacity (WMC) and perceptual load. The operation span test defined subjects with low versus high WMC, who then discriminated target/nontarget tones while EEG was recorded. Infrequent white noise distracters were presented at midline or ±90° locations, and perceptual load was manipulated by varying nontarget frequency. Amplitude of the N100 to distracters was negatively correlated with WMC. Relative to targets, only high WMC subjects showed attenuated N100 amplitudes to nontargets. In the higher WMC group, increased perceptual load was associated with decreased P3a amplitudes to distracters and longer-lasting negative slow wave to nontargets. Results show that auditory cortical processing is associated with multiple facets of attention related to WMC and possibly higher-level cognition.

Sensation seeking predicts brain responses in the old-new task: converging multimodal neuroimaging evidence

Novel images and message content enhance visual attention and memory for high sensation seekers, but the neural mechanisms associated with this effect are unclear. To investigate the individual differences in brain responses to new and old (studied) visual stimuli, we utilized event-related potentials (ERP) and functional Magnetic Resonance Imaging (fMRI) measures to examine brain reactivity among high and low sensation seekers during a classic old-new memory recognition task. Twenty low and 20 high sensation seekers completed separate, but parallel, ERP and fMRI sessions. For each session, participants initially studied drawings of common images, and then performed an old-new recognition task during scanning. High sensation seekers showed greater ERP responses to new objects at the frontal N2 ERP component, compared to low sensation seekers. The ERP Novelty-N2 responses were correlated with fMRI responses in the orbitofrontal gyrus. Sensation seeking status also modulated the FN400 ERP component indexing familiarity and conceptual learning, along with fMRI responses in the caudate nucleus, which correlated with FN400 activity. No group differences were found in the late ERP positive components indexing classic old-new amplitude effects. Our combined ERP and fMRI results suggest that sensation-seeking personality affects the early brain responses to visual processing, but not the later stage of memory recognition.

Electrophysiological evidence for late maturation of strategic episodic retrieval processes

Improvement in source memory performance throughout development is thought to be mediated by strategic processes that facilitate the retrieval of task-relevant information. Using event-related potentials (ERPs), we examined developmental changes in these processes during adolescence. Adolescents (13-14 years) and adults (19-29 years) completed a memory exclusion task which required the discrimination between words studied in one color ('targets') and words studied in the alternative color ('non-targets') under two conditions that put different demands on strategic control. Memory accuracy improved with age and also increased with decreasing control demands in both age groups. The parietal old/new effect, an ERP correlate of recollection, was reliable for targets across conditions in both age groups. By contrast, ERP correlates of non-target recollection were present in adolescents across conditions but not in adults. This suggests that adults implemented a strategy to prioritize recollection of target information with greater success than adolescents regardless of control demands, presumably reflecting maturational differences in cognitive control. In support of this view, the ERP amplitude difference between targets and non-targets was positively correlated with a measure of working memory capacity (WMC) in adults but not in adolescents. A further age-related difference was that ERP correlates of post-retrieval processing, including late right-frontal old/new effects and late posterior negativities, were observed in adults only. Together, our data suggest protracted maturation in the strategic processes that underlie selective recollection and post-retrieval control.

Two hemispheres for better memory in old age: role of executive functioning

This experiment explored the functional significance of age-related hemispheric asymmetry reduction associated with episodic memory and the cognitive mechanisms that mediate this brain pattern. ERPs were recorded while young and older adults performed a word-stem cued-recall task. Results confirmed that the parietal old/new effect was of larger latency and reduced magnitude and less lateralized in the older group than the young group. Correlational and regression analyses indicated that the degree of laterality of brain activity determines the accuracy of memory performance and mediates age-related differences in memory performance among older participants. They also confirmed a cascade model in which the individual level of executive functioning of older adults mediates age-related differences in the degree of lateralization of brain activity, which in turn mediates age-related differences in memory performance.