Left Parietal Effect Research Articles

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.

Level of processing’s effect on episodic retrieval following traumatic brain injury in the elderly: An event-related potential study

Individuals who have sustained a traumatic brain injury (TBI) can suffer from episodic memory impairments. Until now, the neural correlates underlying episodic retrieval in individuals with TBI remained scarce, particularly in older adults. We aimed to fill this gap by recording event-related potentials during an old/new episodic recognition task in 26 older adults, 13 healthy and 13 with TBI. The task manipulated the level of processing in encoding with the use of semantic organizational strategies (deep guided, deep self-guided, and shallow encoding). For all encoding conditions, behavioral data analyses on the discrimination rate indicated that older adults with TBI were globally impaired compared with healthy older adults. The electrophysiological results indicated that the left-parietal effect was larger in the deep guided condition than in the shallow condition. In addition, the results show that the mid-frontal and left-parietal positive old/new effects were absent in both groups. The main findings are the observation, in the control group only, of an early frontal old/new effect (P200; 150–300 ms) and of a late frontal old/new effect on the left hemisphere, only in the Spontaneous condition. Together, results suggest an impairment of the allocation of attentional resources and working memory necessary for retrieving and monitoring items in the elderly with TBI.

Age differences in the neural correlates of the specificity of recollection: An event-related potential study

In young adults, the neural correlates of successful recollection vary with the specificity (or amount) of information retrieved. We examined whether the neural correlates of recollection are modulated in a similar fashion in older adults. We compared event-related potential (ERP) correlates of recollection in samples of healthy young and older adults (N = 20 per age group). At study, participants were cued to make one of two judgments about each of a series of words. Subsequently, participants completed a memory test for studied and unstudied words in which they first made a Remember/Know/New (RKN) judgment, followed by a source memory judgment when a word attracted a ‘Remember’ (R) response. In young adults, the ‘left parietal effect’ – a putative ERP correlate of successful recollection – was largest for test items endorsed as recollected (R judgment) and attracting a correct source judgment, intermediate for items endorsed as recollected but attracting an incorrect or uncertain source judgment, and, relative to correct rejections, absent for items endorsed as familiar only (K judgment). In marked contrast, the left parietal effect was not detectable in older adults. Rather, regardless of source accuracy, studied items attracting an R response elicited a sustained, centrally maximum negative-going deflection relative to both correct rejections and studied items where recollection failed (K judgment). A similar retrieval-related negativity has been described previously in older adults, but the present findings are among the few to link this effect specifically to recollection. Finally, relative to correct rejections, all classes of correctly recognized old items elicited an age-invariant, late-onsetting positive deflection that was maximal over the right frontal scalp. This finding, which replicates several prior results, suggests that post-retrieval monitoring operations were engaged to an equivalent extent in the two age groups. Together, the present results suggest that there are circumstances where young and older adults engage qualitatively distinct retrieval-related processes during successful recollection.

Cognitive control depletion reduces pre-stimulus and recollection-related measures of strategic retrieval.

Background: The ability to strategically retrieve task-relevant information from episodic memory is thought to rely on goal-directed executive processes, and there is evidence that neural correlates of strategic retrieval are sensitive to reserves of cognitive control. The present study extended this work, exploring the role of cognitive control in the flexible orienting of strategic retrieval processes across alternating retrieval goals. Method: Pre-stimulus cues directed participants to endorse memory targets from one of two encoding contexts, with the target encoding context alternating every two trials. Items from the nontarget encoding context were rejected alongside new items. One group of participants completed a Stroop task prior to the memory test in order to deplete their reserves of cognitive control, while a second group performed a control task. Event-related potentials (ERPs) were recorded throughout the memory task, and time-locked to both pre-stimulus cues and memory probes. Results: Control participants' pre-stimulus ERPs showed sustained divergences at frontal electrode sites according to retrieval goal. This effect was evident on the first trial of each memory task, and linked with the initiation of goal-specific retrieval orientations. Control participants also showed enhanced ERP correlates of recollection (the 'left parietal effect') for correctly classified targets relative to nontargets on the second trial of each memory task, indexing strategic retrieval of task-relevant information. Both the pre-stimulus index of retrieval orientation and the target/nontarget left parietal effect were significantly attenuated in participants that completed the Stroop task. Conclusions: The reduction of pre-stimulus and stimulus-locked ERP effects following the Stroop task indicates that available reserves of cognitive control play an important role in both proactive and recollection-related aspects of strategic retrieval.

Cognitive control depletion reduces pre-stimulus and recollection-related measures of strategic retrieval

Background: The ability to strategically retrieve task-relevant information from episodic memory is thought to rely on goal-directed executive processes, and there is evidence that neural correlates of strategic retrieval are sensitive to reserves of cognitive control. The present study extended this work, exploring the role of cognitive control in the flexible orienting of strategic retrieval processes across alternating retrieval goals. Method: Pre-stimulus cues directed participants to endorse memory targets from one of two encoding contexts, with the target encoding context alternating every two trials. Items from the nontarget encoding context were rejected alongside new items. One group of participants completed a Stroop task prior to the memory test in order to deplete their reserves of cognitive control, while a second group performed a control task. Event-related potentials (ERPs) were recorded throughout the memory task, and time-locked to both pre-stimulus cues and memory probes. Results: Control participants’ pre-stimulus ERPs showed sustained divergences at frontal electrode sites according to retrieval goal. This effect was evident on the first trial of each memory task, and linked with the initiation of goal-specific retrieval orientations. Control participants also showed enhanced ERP correlates of recollection (the ‘left parietal effect’) for correctly classified targets relative to nontargets on the second trial of each memory task, indexing strategic retrieval of task-relevant information. Both the pre-stimulus index of retrieval orientation and the target/nontarget left parietal effect were significantly attenuated in participants that completed the Stroop task. Conclusions: The reduction of pre-stimulus and stimulus-locked ERP effects following the Stroop task indicates that available reserves of cognitive control play an important role in both proactive and recollection-related aspects of strategic retrieval.

Cognitive control depletion reduces pre-stimulus and recollection-related measures of strategic retrieval.

Background: The ability to strategically retrieve task-relevant information from episodic memory is thought to rely on goal-directed executive processes, and there is evidence that neural correlates of strategic retrieval are sensitive to reserves of cognitive control. The present study extended this work, exploring the role of cognitive control in the flexible orienting of strategic retrieval processes across alternating retrieval goals. Method: Pre-stimulus cues directed participants to endorse memory targets from one of two encoding contexts, with the target encoding context alternating every two trials. Items from the nontarget encoding context were rejected alongside new items. One group of participants completed a Stroop task prior to the memory test in order to deplete their reserves of cognitive control, while a second group performed a control task. Event-related potentials (ERPs) were recorded throughout the memory task, and time-locked to both pre-stimulus cues and memory probes. Results: Control participants' pre-stimulus ERPs showed sustained divergences at frontal electrode sites according to retrieval goal. This effect was evident on the first trial of each memory task, and linked with the initiation of goal-specific retrieval orientations. Control participants also showed enhanced ERP correlates of recollection (the 'left parietal effect') for correctly classified targets relative to nontargets on the second trial of each memory task, indexing strategic retrieval of task-relevant information. Both the pre-stimulus index of retrieval orientation and the target/nontarget left parietal effect were significantly attenuated in participants that completed the Stroop task. Conclusions: The reduction of pre-stimulus and stimulus-locked ERP effects following the Stroop task indicates that available reserves of cognitive control play an important role in both proactive and recollection-related aspects of strategic retrieval.

An item's status in semantic memory determines how it is recognized: Dissociable patterns of brain activity observed for famous and unfamiliar faces

Are all faces recognized in the same way, or does previous experience with a face change how it is retrieved? Previous research using human scalp-recorded Event-Related Potentials (ERPs) demonstrates that recognition memory can produce dissociable brain signals under a variety of circumstances. While many studies have reported dissociations between the putative ‘dual processes’ of familiarity and recollection, a growing number of reports demonstrate that recollection itself may be fractionated into component processes. Many recognition memory studies using lexical materials as stimuli have reported a left parietal ERP old/new effect for recollection; however, when unfamiliar faces are recollected, an anterior effect can be observed. This paper addresses two separate hypotheses concerning the functional significance of the anterior old/new effect: perceptual retrieval and semantic status. The perceptual retrieval view is that the anterior effect reflects reinstatement of perceptual information bound up in an episodic representation, while the semantic status view is that information not represented in semantic memory pre-experimentally elicits the anterior effect instead of the left parietal effect. We tested these two competing accounts by investigating recognition memory for unfamiliar faces and famous faces in two separate experiments, in which same or different pictures of studied faces were presented as test items to permit brain activity associated with retrieving face and perceptual information to be examined independently. The difference in neural activity between same and different picture hits was operationalized as a pattern of activation associated with perceptual retrieval; while the contrast between different picture hits and correct rejection of new faces was assumed to reflect face retrieval. In Experiment 1, using unfamiliar faces, the anterior old/new effect (500–700 ms) was observed for face retrieval but not for perceptual retrieval, challenging the perceptual retrieval hypothesis. In Experiment 2, using famous faces, face retrieval was associated with a left parietal effect (500–700 ms), supporting the semantic representation hypothesis. A between-subjects analysis comparing scalp topography across the two experiments found that the anterior effect observed for unfamiliar faces is dissociable from the left parietal effect found for famous faces. This pattern of results supports the hypothesis that an item's status in semantic memory determines how it is recognized.

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.

Electrophysiological Evidence for the Continuous Processing of Linguistic Categories of Regular and Irregular Verb Inflection in German

A central question concerning word recognition is whether linguistic categories are processed in continuous or categorical ways, in particular, whether regular and irregular inflection is stored and processed by the same or by distinct systems. Here, we contribute to this issue by contrasting regular (regular stem, regular suffix) with semi-irregular (regular stem, irregular suffix) and irregular (irregular stem, irregular suffix) participle formation in a visual priming experiment on German verb inflection. We measured ERPs and RTs and manipulated the inflectional and meaning relatedness between primes and targets. Inflected verb targets (e.g., leite, "head") were preceded either by themselves, by their participle (geleitet, "headed"), by a semantically related verb in the same inflection as the target (führe, "guide") or in the participle form (geführt, "guided"), or by an unrelated verb in the same inflection (nenne, "name"). Results showed that behavioral and ERP priming effects were gradually affected by verb regularity. Regular participles produced a widely distributed frontal and parietal effect, irregular participles produced a small left parietal effect, and semi-irregular participles yielded an effect in-between these two in terms of amplitude and topography. The behavioral and ERP effects further showed that the priming because of participles differs from that because of semantic associates for all verb types. These findings argue for a single processing system that generates participle priming effects for regular, semi-irregular, and irregular verb inflection. Together, the findings provide evidence that the linguistic categories of verb inflection are processed continuously. We present a single-system model that can adequately account for such graded effects.

Immediate judgments of learning predict subsequent recollection: Evidence from event-related potentials.

Judgments of learning (JOLs) are assessments of how well materials have been learned. Although a wide body of literature has demonstrated a reliable correlation between memory performance and JOLs, relatively little is known about the nature of this link. Here, we investigate the relationship between JOLs and the memory retrieval processes engaged on a subsequent memory test. Participants first studied cue-target word pairs and assigned JOLs to each. Later, memory for the cue word in each pair was assessed using an old/new recognition memory task, and electrophysiological measures of familiarity and recollection were examined. Recognition accuracy was superior for materials given high rather than low JOLs. Analysis of event-related potentials (ERPs) revealed that for both high and low JOL items, successful recognition elicited correlates of familiarity (the mid-frontal effect) and recollection (the left-parietal effect). Importantly, however, the magnitude of the familiarity correlate was equal for high and low JOL items, whereas the magnitude of the recollection correlate was significantly larger for items given high JOLs. These findings demonstrate that JOLs made at study correlate with memory retrieval at test-but that this correlation is specific to recollection. The electrophysiological data support the broader view that participants focus on contextual cues when making JOLs, which may later aid recollection.

Lexical Quality in the Brain: ERP Evidence for Robust Word Learning From Context

We examined event-related potentials (ERPs) before and after word learning, using training contexts that differed in their level of contextual support for meaning acquisition. Novel words appeared either in contexts that were semantically constraining, providing strong cues to meaning, or in contexts that were weakly constraining, that is, uninformative. After each sentence, participants were shown the word in isolation and were asked to generate a close synonym. Immediately after training, words trained in high-constraint contexts elicited a smaller left temporal negativity (N300FT7) compared with words trained in low-constraint contexts, and both types of trained words elicited a stronger medial frontal negativity (N350Fz) relative to familiar words. Two days after training the N300FT7 disappeared and was replaced by a later, left parietal (P600Pz) effect. To examine robust learning, we administered a semantic priming test two days after training. Familiar words and words trained in high-constraint contexts elicited strong N400 effects. By contrast, words trained in low-constraint contexts elicited a weak N400 effect, and novel (untrained rare) words elicited no semantic priming. These findings suggest that supportive contexts and the use of an active meaning-generation task may lead to robust word learning. The effects of this training can be observed as changes in an early left frontal component, as well as the classical N400 effect. We discuss implications for theories of “partial” semantic knowledge and for robust word learning and instruction.

The amount of retrieval support modulates age effects on episodic memory: Evidence from event-related potentials

This experiment was designed to explore the impact of age and amount of retrieval support on episodic memory and its electrophysiological correlates. Event-related potentials (ERPs) were recorded while young and older participants performed a word-stem cued-recall task in a low-support condition (LSC) in which the stem was composed of three letters, and a high-support condition (HSC) in which the cue consisted of four letters. Behavioral analyses showed that recall in the older group was less accurate than in the young group in the LSC, but no age differences were observed in the HSC. In the LSC, old/new ERP effects at frontal and parietal sites were later and less sustained for the older adults. Furthermore, the parietal old/new effect was symmetrically distributed for older adults, whereas it was predominant over the left hemisphere for their younger counterparts. In addition, young participants demonstrated early and long-lasting frontal and parietal effects in the HSC but with predominance over the right hemisphere, whereas the older adults exhibited a frontal effect and an early and long-lasting parietal effect becoming predominant over the left hemisphere. No age differences in the time course of the parietal old/new effect were observed in this more supportive condition. In addition, in the last period, the left parietal effect was greater for the older group. This study suggests that episodic memory performance and ERP correlates of recall processes are more similar between young and older adults when increased support is provided at retrieval.

Mind Wandering and Retrieval from Episodic Memory: A Pilot Event-Related Potential Study

The present study investigated the effects of mind wandering (task-unrelated thought) on the subcomponents of episodic memory as reflected by event-related potentials (ERPs). Specifically, individual differences in the pattern of ERP episodic 'old/new' effects (left-parietal, right-frontal and central-negativity effects) were examined across groups of participants experiencing either high or low frequencies of task-unrelated thought during encoding. Twenty participants studied lists of words and line drawings in one of two contexts (red versus green coloured boxes). At test, participants discriminated between target (old words or line drawings presented in one colour) and nontargets (old items from the other colour and new items). On completion of the memory task, participants completed the 'thinking' component of the Dundee Stress State Questionnaire to provide a retrospective measure of task-unrelated thought. Behavioural data indicated that irrespective of the presence of task-unrelated thought, participants were able to complete the memory task equally well. However, an analysis of ERPs across High and Low task-unrelated thought groups revealed differences in retrieval strategy. Those individuals with infrequent episodes of task-unrelated thought at study used a 'pure' recollection strategy (left-parietal effect only). Conversely, those participants experiencing frequent episodes of task-unrelated thought were unable to recollect the stimuli with ease, as indexed by a diminished parietal effect. As a consequence, these participants employed additional strategic processes for task completion, as indexed by an elevated amplitude of central negativity effects. These data are consistent with the decoupling hypothesis of mind wandering which suggests impaired recollection when attention becomes directed away from the task.

Electrophysiological evidence for the effect of interactive imagery on episodic memory: Encouraging familiarity for non-unitized stimuli during associative recognition

Episodic memory depends upon multiple processes, including familiarity and recollection. Although associative recognition tasks are traditionally viewed as requiring recollection, recent research suggests a role for familiarity if to-be-remembered stimuli are perceived as unitized. Here we use event-related potentials (ERPs) to examine the relationship between stimulus properties and encoding strategy on the engagement of familiarity during associative recognition. Participants studied word pairs containing an association (e.g. traffic–jam) or an unassociated semantic relationship (e.g. violin–guitar), using either item or interactive imagery. At test, participants were required to recognize if word pairs were presented in the same pairing as study, were rearranged, or new. We hypothesized that adopting a strategy of interactive imagery during encoding (i.e. encouraging unitization) would enhance familiarity for unassociated word pairs but would have no effect on association pairs because they are already perceived as unitized. As expected, overall recognition performance was better for word pairs encoded with interactive imagery, and for association than semantic word pairs. ERPs recorded at test revealed an interaction between encoding strategy and stimulus properties. Association word pairs elicited similar bilateral frontal (familiarity) and left parietal (recollection) old/new effects following item and interactive imagery. By contrast, for semantic word pairs, the left parietal effect was equivalent across conditions, but the bilateral frontal effect was enhanced for the interactive imagery condition. The ERP results suggest that an encoding strategy of interactive imagery can enhance familiarity during associative recognition, but this effect is ultimately dependent on the properties of the stimuli to-be-remembered and the nature of the representations that underlie them.

An Electrophysiological Investigation of Factors Facilitating Strategic Recollection

Episodic memory is thought to be mediated by executive processes that facilitate the retrieval of task-relevant information at the expense of irrelevant information. The exclusion task [A process dissociation framework: Separating automatic from intentional uses of memory. Journal of Memory and Language, 30, 513-541, 1991] can be used to explore these processes. In this task, studied items from one source ("targets") are endorsed on one response key, whereas new and studied items from another source ("nontargets") are rejected on another key. Herron and Rugg [Strategic influences on recollection in the exclusion task: Electrophysiological evidence. Psychonomic Bulletin and Review, 10, 703-710, 2003] reported that nontargets elicited the ERP correlate of recollection (the "left parietal old/new effect") when target accuracy was low, but not when it was high. Their explanation for this was that participants only focused exclusively on the recollection of target information when the likelihood of target recollection was high, as under these conditions this strategy is one that that will give rise to accurate task performance. The fact, however, that targets were encoded in different tasks in the high- and low-accuracy groups means that the results can also be explained in terms of the encoding operations performed at study rather than in terms of target accuracy. This study was designed to distinguish between these competing accounts. All targets were encoded elaboratively. Target accuracy was reduced in one condition with a 40-min study-test interval. Nontargets elicited no left parietal effect in either condition, suggesting that target-specific strategic retrieval is facilitated by certain classes of encoding operations rather than simply high target accuracy per se.

Recognition memory for emotionally negative and neutral words: an ERP study

Scalp recorded event-related potentials were used to investigate the neural activity elicited by emotionally negative and emotionally neutral words during the performance of a recognition memory task. Behaviourally, the principal difference between the two word classes was that the false alarm rate for negative items was approximately double that for the neutral words. Correct recognition of neutral words was associated with three topographically distinct ERP memory ‘old/new’ effects: an early, bilateral, frontal effect which is hypothesised to reflect familiarity-driven recognition memory; a subsequent left parietally distributed effect thought to reflect recollection of the prior study episode; and a late onsetting, right-frontally distributed effect held to be a reflection of post-retrieval monitoring. The old/new effects elicited by negative words were qualitatively indistinguishable from those elicited by neutral items and, in the case of the early frontal effect, of equivalent magnitude also. However, the left parietal effect for negative words was smaller in magnitude and shorter in duration than that elicited by neutral words, whereas the right frontal effect was not evident in the ERPs to negative items. These differences between neutral and negative words in the magnitude of the left parietal and right frontal effects were largely attributable to the increased positivity of the ERPs elicited by new negative items relative to the new neutral items. Together, the behavioural and ERP findings add weight to the view that emotionally valenced words influence recognition memory primarily by virtue of their high levels of ‘semantic cohesion’, which leads to a tendency for ‘false recollection’ of unstudied items.