Episodic priming and memory for temporal source: event-related potentials reveal age-related differences in prefrontal functioning

A meta-analysis of event-related potential correlates of recognition memory

A longstanding question in memory research is whether recognition is supported by more than one mnemonic process. Dual-process models distinguish recollection of episodic detail from familiarity, while single-process models explain recognition in terms of one process that varies in strength. Dual process models have drawn support from findings that recollection and familiarity elicit distinct electroencephalographic event-related potentials (ERPs): a mid-frontal ERP effect that occurs at around 300-500 ms post-stimulus onset and is often larger for familiarity than recollection contrasts, and a parietal ERP effect that occurs at around 500-800 ms and is larger for recollection than familiarity contrasts. We sought to adjudicate between dual- and single-process models by investigating whether the dissociation between these two ERP effects is reliable over studies. We extracted effect sizes from 41 experiments that had used Remember-Know, source memory, and associative memory paradigms (1,000 participants). Meta-analysis revealed a strong interaction between ERP effect and mnemonic process of the form predicted by dual-process models. Although neither ERP effect was significantly process-selective taken alone, a moderator analysis revealed a larger mid-frontal effect for familiarity than recollection contrasts in studies using the Remember-Know paradigm. Mega-analysis of raw data from six studies further showed significant process-selectivity for both mid-frontal and parietal ERPs in the predicted time windows. On balance, the findings favor dual- over single-process theories of recognition memory, but point to a need to promote sharing of raw data.

Brain electrophysiological responses associated with the retrieval of temporal and spatial contexts in episodic memory

Episodic memory allows us to remember three main elements regarding an event: what (it is), where (it is in space), and when (it appears). The brain's electrical activity signaling the occurrence of these processes has been studied separately, revealing different patterns of ERP components and changes in the EEG theta band amplitude. However, how these patterns signal the retrieval of the temporal and spatial contexts of the same episode is unknown. The objective of this study was to evaluate the ERP components and the EEG theta band in association to the retrieval of the what, where, and when of the same episode through a source memory task. Three types of trials were identified here: total retrieval (what, where, and when), spatial retrieval (what and where), and correct rejections (correctly identified as new items). Attentional components, N200 and P300, and theta band were sensitive to the amount of information retrieved from episodic memory. Total retrieval and spatial trials elicited higher mean amplitude of FN400 and LPC, familiarity and recollection markers, respectively, than correct rejections. Our results suggest that early attention mechanisms can discern the strength of retrieval; in turn, familiarity and recollection mechanisms participate in the retrieval of the main contexts of episodic memory, but not in a cumulative way.

Can the elderly take the action? - The influence of unitization induced by action relationships on the associative memory deficit

Healthy aging is associated with intact familiarity, whereas recollection, usually supporting associative memory, is attenuated. Accordingly, associative memory shows a stronger age-related decline than item memory. One approach to alleviate age-related associative memory deficits is to increase the contribution of familiarity to associative memory by creating encoding conditions that allow to integrate separate stimuli to an entity (unitization). The current study investigated whether bottom-up unitization can reduce age-related differences in associative memory. Younger (YA) and older adults (OA) studied associations between semantically unrelated objects, spatially arranged in a way that an action between these two objects is possible (unitized, e.g., emptying a bottle into a sneaker) or not (non-unitized). At test, participants distinguished intact from recombined and new object pairs. As expected, we found larger age differences for associative memory than for item memory. Additionally, the presence of action relationships supports memory performance in both age groups. In the event-related potentials (ERP) of the test phase, we observed an age-related attenuation of recollection and preserved familiarity independent of the action relationship condition. Considering comparisons including the recombined pairs, the ERP correlate of associative familiarity (i.e., intact vs. recombined) was present in OA for action-related pairs, whereas for YA, there was no evidence for enhanced familiarity for action-related pairs. In the late time window, ERP evidence for recollection for intact action-related object pairs was obtained independent of age group. In conclusion, both age groups benefited from unitization by action relationships but by different mechanisms. While YA show no associative familiarity for action-related object pairs but a general reliance on recollection for associations in action-related and -unrelated pairs, OA seem to rely more on familiarity for the specific arrangement of action-related pairs.

Adapting event-related potential research paradigms for children: Considerations from research on the development of recognition memory

Most developmental event-related potential (ERP) research uses experimental paradigms modified from research with adults. One major challenge is identifying how to adapt these paradigms effectively for use with younger individuals. This paper provides guidance for developmental adaptations by considering research on the development of recognition memory. We provide a brief overview of recognition memory tasks and ERP components associated with recognition memory in children and adults. Then, we provide some general recommendations, discuss common differences between ERP studies of recognition memory in adults and children (e.g., the type of stimuli presented, response modalities), and provide suggestions for assessing the effect of task modifications on ERP components of interest. Specifically, we recommend (a) testing both children and adults on the modified paradigm to allow for a continuity of findings across development, (b) comparing children of different ages on the modified paradigm based on expectations regarding when developmental change occurs for the cognitive process of interest, and (c) empirically assessing the effect of methodological differences between paradigms. To illustrate the latter, we analyzed data from our lab comparing memory-related ERP components when children experienced a 1-day, 2-day, or 1-week delay between encoding and retrieval.

Interactions of Emotion and Self-reference in Source Memory: An ERP Study

The way emotional information is encoded (e.g., deciding whether it is self-related or not) has been found to affect source memory. However, few studies have addressed how the emotional quality and self-referential properties of a stimulus interactively modulate brain responses during stimulus encoding and source memory recognition. In the current study, 22 participants completed five study-test cycles with negative, neutral, and positive words encoded in self-referential versus non-self-referential conditions, while event-related potentials of the electroencephalogram were recorded. An advantage of self-referential processing in source memory performance, reflected in increased recognition accuracy, was shown for neutral and positive words. At the electrophysiological level, self-referential words elicited increased amplitudes in later processing stages during encoding (700-1,200 ms) and were associated with the emergence of old/new effects in the 300-500 ms latency window linked to familiarity effects. In the 500-800 ms latency window, old/new effects emerged for all valence conditions except for negative words studied in the non-self-referential condition. Negative self-referential words also elicited a greater mobilization of post-retrieval monitoring processes, reflected in an enhanced mean amplitude in the 800-1,200 ms latency window. Together, the current findings suggest that valence and self-reference interactively modulate source memory. Specifically, negative self-related information is more likely to interfere with the recollection of source memory features.

Examining the development of memory for temporal context and its underlying neural processes using event-related potentials

•

Memory for temporal context, vital for episodic memory, shows prolonged development.

•

Cognitive processes and neural mechanisms driving age-related improvements unclear.

•

Event-related potentials (ERP) used with 7−9-year-olds, 10−12-year-olds, and adults.

•

We found age-related improvements, ERP effects, and brain-behavior relations.

•

Implications for temporal memory and episodic memory development discussed.

Time is a critical feature of episodic memory—memory for events from a specific time and place (Tulving, 1972). Previous research indicates that temporal memory (memory for ‘when’) is slower to develop than memory for other details (e.g., ‘what’ and ‘where’), with improvements observed across middle and late childhood. The factors that drive these changes are not yet clear. We used an event-related potential (ERP) recognition memory paradigm to investigate the underlying processes of memory for temporal context in middle to late childhood (7−9-year-olds; 10−12-year-olds) and young adulthood. Behaviorally, we observed age-related improvements in the ability to place events in temporal context. ERP analyses showed old/new effects for children and adults. We also found brain-behavior relations for 1) episodic memory (ERP mean amplitude difference between source hits and correctly identified new trials was correlated to behavioral accuracy), and 2) temporal memory (ERP mean amplitude difference between source hits and source error trials was correlated to accuracy of temporal memory judgments). This work furthers our understanding of the cognitive processes and neural signatures supporting temporal memory development in middle to late childhood, and has implications for episodic memory development more broadly.

EEG-Based Prediction of Successful Memory Formation During Vocabulary Learning

Previous Electroencephalography (EEG) and neuroimaging studies have found differences between brain signals for subsequently remembered and forgotten items during learning of items - it has even been shown that single trial prediction of memorization success is possible with a few target items. There has been little attempt, however, in validating the findings in an application-oriented context involving longer test spans with realistic learning materials encompassing more items. Hence, the present study investigates subsequent memory prediction within the application context of foreign-vocabulary learning. We employed an off-line, EEG-based paradigm in which Korean participants without prior German language experience learned 900 German words in paired-associate form. Our results using convolutional neural networks optimized for EEG-signal analysis show that above-chance classification is possible in this context allowing us to predict during learning which of the words would be successfully remembered later.

Motivated forgetting increases the recall time of learnt items: Behavioral and event related potential evidence

We investigated modulation of the recall time in a motivated forgetting (MF) paradigm and the neural manifestation of it through event related potential (ERP) analysis. We studied whether compared to failed attempts in suppression, partial success can potentiate control mechanisms and this might manifest, neurally as modulation of ERP components related to conscious recollection, and behaviorally as delayed recall of learnt items. We employed a modified version of the Think\No-Think paradigm with dominant number of No-Think words (cued to forget). We defined a forgetting index as FI = Final Recall Time-Initial Recall Time. The MF trials were separated into three conditions according to their corresponding FI; Forget, Delayed Recall, and Recall conditions. The findings revealed significant late ERP effects in terms of a late parietal positivity (LPP), modulated by the item condition, that appeared to reflect the consequence of conscious suppression on actual retrieval of stored memory. Over the same topographic location, FI was negatively correlated with the LPP amplitude, demonstrating the consequence of inhibition processing during MF in modulating the recall time. The negative correlation between LPP and FI provides evidence that increased recall time due to MF is also related to reduced activity, probably in the hippocampal-parietal network, corresponding to recollection of suppressed memories.

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.

Orienting and memory to unexpected and/or unfamiliar visual events in children and adults

For children, new experiences occur very often, and learning to differentiate between old and new events is a fundamental process necessary for appropriate reactions to stimuli. Thus the present study is concerned with maturation of brain responses to repeated novel events. We examined the effect of repetition of familiar (meaningful) and unfamiliar (meaningless) symbols on the event-related-potentials (ERPs) recorded during novelty oddball and recognition memory tasks from children, adolescents and young adults. During the novelty oddball task, repetition of the familiar symbols elicited a reduction in the novelty P3 in the ERPs of all age groups, while repetition of the unfamiliar symbols elicited a reduction in novelty P3 amplitude only in children. As expected, recognition memory performance improved with age and was better for familiar than unfamiliar symbols. For all age groups, ERPs to correctly recognized familiar old symbols elicited a larger positivity than ERPs to correctly identified new symbols, indicating a reliable memory effect. However, ERPs to unfamiliar old and new symbols did not differ in adults and adolescents but did differ in children. The data suggest that children process familiar visual symbols in a similar fashion to that of adults, and that children process unfamiliar symbols differently from adults.

Neurobiological basis of feeling of knowing in episodic memory

Feeling of knowing (FOK) is a metacognitive process which allows individuals to predict the likelihood that they will be able to remember, in the future, information which they currently cannot recall. Although FOK provides evidence for the mechanisms of metacognitive systems, the neurobiological basis of FOK is still unclear. We investigated the neural correlates of FOK induced by an episodic memory task in 77 younger adult participants. Data were gathered using event-related potentials (ERPs). ERP components during high, low, extremely high and extremely low FOK judgments were analyzed. Stimulus-locked ERP analyses indicated that FOK judgment was associated with greater positivity for P200 component at frontal, central, and parietal electrode zones and greater negativity for the N200 component at parietal electrode zones. Furthermore, results revealed that amplitude of the ERP components for FOK judgments were affected by the level of FOK judgment. Results suggest that ERP components of FOK judgment observed within a 200 ms time window support the perceptual fluency-based model.

Aging and recognition memory: A meta-analysis

Recognizing a stimulus as previously encountered is a crucial everyday life skill and a critical task motivating theoretical development in models of human memory. Although there are clear age-related memory deficits in tasks requiring recall or memory for context, the existence and nature of age differences in recognition memory remain unclear. The nature of any such deficits is critical to understanding the effects of age on memory because recognition tasks allow fewer strategic backdoors to supporting memory than do tasks of recall. Consequently, recognition may provide the purest measure of age-related memory deficit of all standard memory tasks. We conducted a meta-analysis of 232 prior experiments on age differences in recognition memory. As an organizing framework, we used signal-detection theory (Green & Swets, 1966; Macmillan & Creelman, 2005) to characterize recognition memory in terms of both discrimination between studied items and unstudied lures (d') and response bias or criterion (c). Relative to young adults, older adults showed reduced discrimination accuracy and a more liberal response criterion (i.e., greater tendency to term items new). Both of these effects were influenced by multiple, differing variables, with larger age deficits when studied material must be discriminated from familiar or related material, but smaller when studying semantically rich materials. These results support a view in which neither the self-initiation of mnemonic processes nor the deployment of strategic processes is the only source of age-related memory deficits, and they add to our understanding of the mechanisms underlying those changes. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Process-specific analysis in episodic memory retrieval using fast optical signals and hemodynamic signals in the right prefrontal cortex

OBJECTIVE

Memory is formed by the interaction of various brain functions at the item and task level. Revealing individual and combined effects of item- and task-related processes on retrieving episodic memory is an unsolved problem because of limitations in existing neuroimaging techniques. To investigate these issues, we analyze fast and slow optical signals measured from a custom-built continuous wave functional near-infrared spectroscopy (CW-fNIRS) system.

APPROACH

In our work, we visually encode the words to the subjects and let them recall the words after a short rest. The hemodynamic responses evoked by the episodic memory are compared with those evoked by the semantic memory in retrieval blocks. In the fast optical signal, we compare the effects of old and new items (previously seen and not seen) to investigate the item-related process in episodic memory. The Kalman filter is simultaneously applied to slow and fast optical signals in different time windows.

MAIN RESULTS

A significant task-related HbR decrease was observed in the episodic memory retrieval blocks. Mean amplitude and peak latency of a fast optical signal are dependent upon item types and reaction time, respectively. Moreover, task-related hemodynamic and item-related fast optical responses are correlated in the right prefrontal cortex.

SIGNIFICANCE

We demonstrate that episodic memory is retrieved from the right frontal area by a functional connectivity between the maintained mental state through retrieval and item-related transient activity. To the best of our knowledge, this demonstration of functional NIRS research is the first to examine the relationship between item- and task-related memory processes in the prefrontal area using single modality.

Refining CVLT-II recognition discriminability indices to enhance the characterization of recognition memory changes in healthy aging

The present study examined age-related differences on the four false-positive (FP) error subtypes found on the California Verbal Learning Test-Second Edition yes/no recognition memory trial and the influence of these subtypes on source and novel recognition discriminability (SoRD and NRD, respectively) index calculations. Healthy older (n = 55) adults generally made more FP errors than healthy young adults (n = 57). Accordingly, older adults performed worse than young adults on all SoRD and NRD indices. However, the manner in which FP error subtypes were incorporated into SoRD and NRD index calculations impacted the magnitudes of observed differences between and within the two age groups on SoRD and NRD indices. The present findings underline the importance of examining FP errors in assessments of recognition memory abilities, and using more refined indices of recognition discriminability to further elucidate the nature of age-related recognition memory impairment.

Age-related deficits in selective attention during encoding increase demands on episodic reconstruction during context retrieval: An ERP study

Previous event-related potential (ERP) and neuroimaging evidence suggests that directing attention toward single item-context associations compared to intra-item features at encoding improves context memory performance and reduces demands on strategic retrieval operations in young and older adults. In everyday situations, however, there are multiple event features competing for our attention. It is not currently known how selectively attending to one contextual feature while attempting to ignore another influences context memory performance and the processes that support successful retrieval in the young and old. We investigated this issue in the current ERP study. Young and older participants studied pictures of objects in the presence of two contextual features: a color and a scene, and their attention was directed to the object's relationship with one of those contexts. Participants made context memory decisions for both attended and unattended contexts and rated their confidence in those decisions. Behavioral results showed that while both groups were generally successful in applying selective attention during context encoding, older adults were less confident in their context memory decisions for attended features and showed greater dependence in context memory accuracy for attended and unattended contextual features (i.e., hyper-binding). ERP results were largely consistent between age groups but older adults showed a more pronounced late posterior negativity (LPN) implicated in episodic reconstruction processes. We conclude that age-related suppression deficits during encoding result in reduced selectivity in context memory, thereby increasing subsequent demands on episodic reconstruction processes when sought after details are not readily retrieved.

Compensatory effects of pointing and predictive cueing on age-related declines in visuospatial working memory

In this study, we investigated whether the visuospatial working memory performance of young and older adults would improve if they used a multimodal as compared with a unimodal encoding strategy, and whether or not visual cues would add to this effect. In Experiment 1, participants were presented with trials consisting of an array of squares and an array of circles. They were instructed to point at one type of figure (multimodal encoding strategy) and only to observe the other (unimodal encoding strategy). After each trial, an immediate location recognition test of one of the two arrays followed. In Experiment 2, the same task was used, but a cue was provided, either before or after the encoding phase, indicating which of the two arrays would be tested. Our results showed that a multimodal, as compared with a unimodal, encoding strategy improved visuospatial working memory performance in both young and older adults (Exp. 1), and that adding visual cues to the multimodal but not to the unimodal encoding strategy improved older adults' performance up to the level of young adults (Exp. 2). In both age groups, cueing after encoding led to higher performance in the multimodal than in the unimodal condition when the second array was tested. However, cueing before encoding led to higher performance in the multimodal than in the unimodal condition when the first array of the figure sequence was tested. These results suggest that pointing together with predictive cueing can have beneficial effects on visuospatial working memory, which is especially important for older adults.

Effects of pointing compared with naming and observing during encoding on item and source memory in young and older adults

Research showed that source memory functioning declines with ageing. Evidence suggests that encoding visual stimuli with manual pointing in addition to visual observation can have a positive effect on spatial memory compared with visual observation only. The present study investigated whether pointing at picture locations during encoding would lead to better spatial source memory than naming (Experiment 1) and visual observation only (Experiment 2) in young and older adults. Experiment 3 investigated whether response modality during the test phase would influence spatial source memory performance. Experiments 1 and 2 supported the hypothesis that pointing during encoding led to better source memory for picture locations than naming or observation only. Young adults outperformed older adults on the source memory but not the item memory task in both Experiments 1 and 2. In Experiments 1 and 2, participants manually responded in the test phase. Experiment 3 showed that if participants had to verbally respond in the test phase, the positive effect of pointing compared with naming during encoding disappeared. The results suggest that pointing at picture locations during encoding can enhance spatial source memory in both young and older adults, but only if the response modality is congruent in the test phase.

Electrophysiological evidence for the effects of unitization on associative recognition memory in older adults

Normal aging is associated with greater decline in associative memory relative to item memory due to impaired recollection. Familiarity may also contribute to associative recognition when stimuli are perceived as a 'unitized' representation. Given that familiarity is relatively preserved in older adults, we explored whether age-related associative memory deficits could be attenuated when associations were unitized (i.e., compounds) compared with those non-unitized (i.e., unrelated word pairs). Young and older adults performed an associative recognition task while electroencephalogram (EEG) was recorded. Behavioral results showed that age differences were smaller for recognition of compounds than for unrelated word pairs. ERP results indicated that only compounds evoked an early frontal old/new effect in older adults. Moreover, the early frontal old/new effect was positively correlated with associative discrimination accuracy. These findings suggest that reduced age-related associative deficits under unitized condition may be associated with the presence of familiarity-based retrieval of compounds in older adults.

Sometimes we have to intentionally focus on the details: Incidental encoding and perceptual change decrease recognition memory performance and the ERP correlate of recollection

Prior studies suggest that memory retrieval is based on two independent processes: Recollection and familiarity. Here, we investigated the role of incidental and intentional encoding, and specifically whether perceptual changes between study and test affects behavioral and electrophysiological correlates of both retrieval processes. During retrieval, participants distinguished between identical and changed exemplars as well as novel distractors. Following incidental encoding, participants had difficulty identifying changed exemplars; item and feature recognition increased after intentional encoding, in particular for changed exemplars. Reflecting this increase in memory performance, the ERP correlate of recollection was larger after intentional encoding and for identical item repetitions, whereas the ERP correlate for familiarity was largely unaffected. Pre-response old/new effects corresponding to later aspects of recollection (700-1000 ms relative to stimulus onset) were larger in response-compared to stimulus-locked averages, but also of similar magnitude for identical and changed exemplars. These results corroborate previous findings suggesting that the electrophysiological signature of recollection is modulated as a function of memory performance. The role of task characteristics and material retrieved from memory for modulations in familiarity-based retrieval processes is discussed.

The best of both worlds: emotional cues improve prospective memory execution and reduce repetition errors

Prospective memory (PM) errors are commonly investigated as failures to execute an intended task (e.g., taking medication), and some studies suggest that emotional PM cues significantly reduce such failures. In Experiment 1, we extended these findings and additionally explored whether improved PM performance with emotional cues comes at the expense of performance on the ongoing task. Our results indicated that both younger and older adults are more likely to respond to emotional than to neutral PM cues, but the emotional cues did not differentially disrupt the performance on the ongoing task for either age group. Because older adults are also prone to mistakenly repeating a completed PM task, in Experiment 2 we further examined whether emotional PM cues increased repetition errors for older adults. Despite equivalent opportunity for repetition errors across cue type, older adults committed significantly fewer repetition errors with emotional than with neutral cues. Thus, these experiments demonstrated that older adults can effectively use emotional cues to help them initiate actions and to minimize repetition errors.

Electrophysiological investigation of source memory in early childhood

Recollection is well-characterized in adults and school-aged children, yet little is known about how this ability develops in early childhood. This study utilized a behavioral source memory paradigm and event-related potentials (ERPs) to examine recollection in early childhood. ERPs were compared between items whose context was remembered and forgotten as well as new items. Activity late in the electrophysiological response showed a "recollection" effect, which differentiated items with correct source judgments from all others. This study is unique in that it is the first to provide information regarding the spatiotemporal dynamics of the neural networks underlying recollection during early childhood.

Age-related decline in controlled retrieval: the role of the PFC and sleep

Age-related cognitive impairments often include difficulty retrieving memories, particularly those that rely on executive control. In this paper we discuss the influence of the prefrontal cortex on memory retrieval, and the specific memory processes associated with the prefrontal cortex that decline in late adulthood. We conclude that preretrieval processes associated with preparation to make a memory judgment are impaired, leading to greater reliance on postretrieval processes. This is consistent with the view that impairments in executive control significantly contribute to deficits in controlled retrieval. Finally, we discuss age-related changes in sleep as a potential mechanism that contributes to deficiencies in executive control that are important for efficient retrieval. The sleep literature points to the importance of slow-wave sleep in restoration of prefrontal cortex function. Given that slow-wave sleep significantly declines with age, we hypothesize that age-related changes in slow-wave sleep could mediate age-related decline in executive control, manifesting a robust deficit in controlled memory retrieval processes. Interventions, like physical activity, that improve sleep could be effective methods to enhance controlled memory processes in late life.

Can people strategically control the encoding and retrieval of some morphologic and typographic details of words?

This study investigated whether the encoding and retrieval of plurality information and letter-case information of words in recognition memory can be inhibited. Response-deadline experiments (Hintzman & Curran, 1994) using single words have indicted a controlled processing mode, whereas studies using meaningful sentences (e.g., Jou & Harris, 1991) have indicated an automatic mode of processing plurality information. Two similar opposing views have existed on the processing of letter-case information. The abstractionist view contends that we retain the abstract lexical information and discard the superficial perceptual case information. The proceduralist view holds that perceptual details cannot be separated from the lexical information. Using an intentional and an attention-diverted learning procedure and instructions to ignore plurality and case, we found that subjects experienced a consistent interference effect of changed plurality from study to test but slightly less interference from changed case, suggesting strong automaticity for plurality, and comparatively less automaticity, for case processing.

The effect of interference on temporal order memory for random and fixed sequences in nondemented older adults

Two experiments tested the effect of temporal interference on order memory for fixed and random sequences in young adults and nondemented older adults. The results demonstrate that temporal order memory for fixed and random sequences is impaired in nondemented older adults, particularly when temporal interference is high. However, temporal order memory for fixed sequences is comparable between older adults and young adults when temporal interference is minimized. The results suggest that temporal order memory is less efficient and more susceptible to interference in older adults, possibly due to impaired temporal pattern separation.

Examining ERP correlates of recognition memory: evidence of accurate source recognition without recollection

Recollection is typically associated with high recognition confidence and accurate source memory. However, subjects sometimes make accurate source memory judgments even for items that are not confidently recognized, and it is not known whether these responses are based on recollection or some other memory process. In the current study, we measured event related potentials (ERPs) while subjects made item and source memory confidence judgments in order to determine whether recollection supported accurate source recognition responses for items that were not confidently recognized. In line with previous studies, we found that recognition memory was associated with two ERP effects: an early on-setting FN400 effect, and a later parietal old-new effect [late positive component (LPC)], which have been associated with familiarity and recollection, respectively. The FN400 increased gradually with item recognition confidence, whereas the LPC was only observed for highly confident recognition responses. The LPC was also related to source accuracy, but only for items that had received a high confidence item recognition response; accurate source judgments to items that were less confidently recognized did not exhibit the typical ERP correlate of recollection or familiarity, but rather showed a late, broadly distributed negative ERP difference. The results indicate that accurate source judgments of episodic context can occur even when recollection fails.

Neural correlates of source memory retrieval in young, middle-aged and elderly adults

Event-related potentials (ERPs) were recorded in young (21-27 years old), middle-aged (50-57 years old) and older adults (70-77 years old) to determine whether the decline in source memory that occurs with advancing age coincides with contemporaneous neurophysiological changes. Source memory for the spatial location (quadrant on the screen) of images presented during encoding was examined. The images were shown in the center of the screen during the retrieval task. Retrieval success for source information was characterized by different scalp topographies at frontal electrode sites in young adults relative to middle-aged and older adults. The right frontal effect during unsuccessful retrieval attempts showed amplitude and latency differences across age groups and was related to the ability to discriminate between old and new images only in young adults. These results suggest that the neural correlates of the retrieval success and attempt were affected by age and these effects were present by middle-age.

Towards a cognitive and neurobiological model of motivated forgetting

Historically, research on forgetting has been dominated by the assumption that forgetting is passive, reflecting decay, interference, and changes in context. This emphasis arises from the pervasive assumption that forgetting is a negative outcome. Here, we present a functional view of forgetting in which the fate of experience in memory is determined as much by motivational forces that dictate the focus of attention as it is by passive factors. A central tool of motivated forgetting is retrieval suppression, a process whereby people shut down episodic retrieval to control awareness. We review behavioral, neurobiological, and clinical research and show that retrieval suppression leads us to forget suppressed experiences. We discuss key questions necessary to address to develop this model, relationships to other forgetting phenomena, and the implications of this research for understanding recovered memories. This work provides a foundation for understanding how motivational forces influence what we remember of life experience.

ERP investigation of study-test background mismatch during face recognition in schizophrenia

Old/new effects on event-related potentials (ERP) were explored in 20 patients with schizophrenia and 20 paired comparison subjects during unfamiliar face recognition. Extrinsic perceptual changes - which influence the overall familiarity of an item while retaining face-intrinsic features for use in structural face encoding - were manipulated between the study phase and the test. The question raised here concerns whether these perceptual incongruities would have a different effect on the sense of familiarity and the corresponding behavioral and ERP measures in the two groups. The results showed that schizophrenia patients were more inclined to consider old faces shown against a new background as distractors. This drop in face familiarity was accompanied by the disappearance of ERP old/new effects in this condition, i.e., FN400 and parietal old/new effects. Indeed, while ERP old/new recognition effects were found in both groups when the picture of the face was physically identical to the one presented for study, the ERP correlates of recognition disappeared among patients when the background behind the face was different. This difficulty in disregarding a background change suggests that recognition among patients with schizophrenia is based on a global perceptual matching strategy rather than on the extraction of configural information from the face. The correlations observed between FN400 amplitude, the rejection of faces with a different background, and the reality-distortion scores support the idea that the recognition deficit found in schizophrenia results from early anomalies that are carried over onto the parietal ERP old/new effect. Face-extrinsic perceptual variations provide an opportune situation for gaining insight into the social difficulties that patients encounter throughout their lives.

Effects of age on the neural correlates of familiarity as indexed by ERPs

ERPs were recorded from samples of young (18-29 years) and older (63-77 years) participants while they performed a modified "remember-know" recognition memory test. ERP correlates of familiarity-driven recognition were obtained by contrasting the waveforms elicited by unrecollected test items accorded "confident old" and "confident new" judgments. Correlates of recollection were identified by contrasting the ERPs elicited by items accorded "remember" and confident old judgments. Behavioral analyses revealed lower estimates of both recollection and familiarity in older participants than in young participants. The putative ERP correlate of recollection-the "left parietal old-new effect"-was evident in both age groups, although it was slightly but significantly smaller in the older sample. By contrast, the putative ERP correlate of familiarity-the "midfrontal old-new effect"-could be identified in young participants only. This age-related difference in the sensitivity of ERPs to familiarity was also evident in subgroups of young and older participants, in whom familiarity-based recognition performance was equivalent. Thus, the inability to detect a reliable midfrontal old-new effect in older participants was not a consequence of an age-related decline in the strength of familiarity. These findings raise the possibility that familiarity-based recognition memory depends upon qualitatively different memory signals in older and young adults.

Age-related source memory deficits persist despite superior item memory

Source and item memory for faces of former United States Presidents were assessed in nondemented older adults over 65 years of age (n = 20) and young adults 18 to 25 years of age (n = 20). During the study phase, a male and a female source each presented pictures of faces to the participant one at a time. To assess source memory, the participant was asked to indicate whether a face from the study phase was presented by the male or female. To assess item memory, a study phase face and distractor face were presented and the participant was asked to indicate which was presented previously. Older adults displayed significantly better item memory for the faces of presidents compared to young adults. However, despite showing superior item memory, source memory still was impaired in older adults compared to young adults. The ability of older adults to efficiently integrate source and item information may be compromised to such a large extent that enhanced item memory does not appear to minimize or negate age-related source memory deficits. The findings demonstrate the robust effects of aging on source memory.

Age-related effects on the neural correlates of autobiographical memory retrieval

Older adults recall less episodically rich autobiographical memories (AM), however, the neural basis of this effect is not clear. Using functional MRI, we examined the effects of age during search and elaboration phases of AM retrieval. Our results suggest that the age-related attenuation in the episodic richness of AMs is associated with difficulty in the strategic retrieval processes underlying recovery of information during elaboration. First, age effects on AM activity were more pronounced during elaboration than search, with older adults showing less sustained recruitment of the hippocampus and ventrolateral prefrontal cortex (VLPFC) for less episodically rich AMs. Second, there was an age-related reduction in the modulation of top-down coupling of the VLPFC on the hippocampus for episodically rich AMs. In sum, the present study shows that changes in the sustained response and coupling of the hippocampus and prefrontal cortex (PFC) underlie age-related reductions in episodic richness of the personal past.