Source Memory Task Research Articles

Do young and older adults rely on different processes in source memory tasks? A neuropsychological study.

Source memory has consistently been associated with prefrontal function in both normal and clinical populations. Nevertheless, the exact contribution of this brain region to source memory remains uncertain, and evidence suggests that processes used by young and older adults may differ. The authors explored the extent to which scores on composite measures of neuropsychological tests of frontal and medial temporal function differentially predicted the performance of young and older adults on source memory tasks. Results indicated that a frontal composite measure, consistently associated with source memory performance in older adults, was unrelated to source memory in young adults, although it was sensitive to a demanding working memory task. The memory composite score, however, predicted performance in the young group. In addition, item and source memory were correlated in young but not older people. Findings are discussed in terms of age-related differences in working memory and executive functions, and differential binding processes necessary for item and source memory. The requirement to integrate item and source information at encoding appears to place greater demands on executive or working memory processes in older adults than in younger adults.

Enactment versus conceptual encoding: Equivalent item memory but different source memory

It has been suggested that performing a physical action (enactment) is an optimally effective encoding task, due to the incorporation of motoric information in the episodic memory trace, and later retrieval of that information. The current study contrasts old/new recognition of objects after enactment to a conceptual encoding task of cost estimation. Both encoding tasks yielded high accuracy, and robust differences in brain activity as compared to new objects, but no differences between encoding tasks. These results are not supportive of the idea that encoding by enactment leads to the spontaneous retrieval of motoric information. When participants were asked to discriminate between the two classes of studied objects during a source memory task, perform-encoded objects elicited higher accuracy and different brain activity than cost-encoded objects. The extent and nature of what was retrieved from memory thus depended on its utility for the assigned memory test: object information during the old/new recognition test, but additional information about the encoding task when necessary for a source memory test. Event-related potentials (ERPs) recorded during the two memory tests showed two orthogonal effects during an early (300–800 msec) time window: a differentiation between studied and unstudied objects, and a test-type (retrieval orientation) effect that was equivalent for old and new objects. Later brain activity (800–1300 msec) differentiated perform- from cost-encoded objects, but only during the source memory test, suggesting temporally distinct phases of retrieval.

The relationship between the right frontal old/new ERP effect and post-retrieval monitoring: Specific or non-specific?

Post-retrieval processes are thought to be engaged when the outcome of an attempt to retrieve information from long-term memory must be monitored or evaluated. Previous research employing event-related potentials (ERPs) has implicated a specific ERP modulation – the ‘right frontal old/new effect’ – as a correlate of post-retrieval processing. In two experiments we examined whether the right frontal effect is specifically associated with processing of the products of an episodic retrieval attempt. During study, subjects in both experiments made one of two semantic judgments on serially presented pictures. In experiment 1, one study phase was followed by a source memory task, in which subjects responded ‘new’ to unstudied pictures and signaled the semantic judgment made on each studied picture. A separate study phase was followed by a task in which the studied items required a judgment about their semantic attributes. Robust right frontal effects were elicited by old items in both tasks, indicating that the effects are not selective for the monitoring of the content of information retrieved from episodic memory. In experiment 2, separate study phases were followed by test phases where semantic judgments were made either on old items (as in experiment 1), or on new items. Right frontal effects were elicited by whichever class of items, old or new, required the semantic judgment. Together, these findings indicate that the right frontal old/new effect reflects generic monitoring or decisional processes, rather than processing dedicated to the evaluation of the products of an episodic retrieval attempt.

Cortical network dynamics during source memory retrieval: Current density imaging with individual MRI

We investigated the neural correlates of source memory retrieval using low-resolution electromagnetic tomography (LORETA) with 64 channels EEG and individual MRI as a realistic head model. Event-related potentials (ERPs) were recorded while 13 healthy subjects performed the source memory task for the voice of the speaker in spoken words. The source correct condition of old words elicited more positive-going potentials than the correct rejection condition of new words at 400-700 ms post-stimulus and the old/new effects also appeared in the right anterior region between 1,000 and 1,200 ms. We conducted source reconstruction at mean latencies of 311, 604, 793, and 1,100 ms and used statistical parametric mapping for the statistical analysis. The results of source analysis suggest that the activation of the right inferior parietal region may reflect retrieval of source information. The source elicited by the difference ERPs between the source correct and source incorrect conditions exhibited dynamic change of current density activation in the overall cortices with time during source memory retrieval. These results indicate that multiple neural systems may underlie the ability to recollect context.

Distinguishing familiarity-based from source-based memory performance in patients with schizophrenia

Background There is substantial current interest in the cognitive deficits associated with schizophrenia, particularly those in the realm of memory. Yet the exact nature of these deficits remains a matter of some debate. This study sought to examine performance on two distinct aspects of memory performance: familiarity-based and source-based memory processes. Methods Eighteen medicated outpatients with schizophrenia and eighteen healthy adult control subjects performed an external source memory task. Key measures included the ability to distinguish old (previously experienced) items from new items, the ability to correctly identify the source (male voice or female voice) of previously experienced items, and the reaction time associated with these responses. Results Patients with schizophrenia showed an impaired ability to distinguish old from new items, but intact performance in correctly identifying the source of items recognized as old. Whereas control subjects showed a rapid response to items deemed unfamiliar, particularly in rejecting novel items, these responses were slowed in patients with schizophrenia. This was not attributable to a generalized diminution in processing speed, as reaction times to correctly recognized old items (regardless of source accuracy) did not differ between the two groups. Conclusions Patients with schizophrenia demonstrated impaired familiarity-based and intact source-based memory performance. In addition, the reaction time for novelty detection, an important component of familiarity-based memory, was significantly delayed in patients compared to controls, while the response times for source-based decisions were completely overlapping. Considered together, these findings suggest a deficit in the familiarity-based aspect of episodic memory in at least some patients with schizophrenia.

Effects of Hormone Replacement Therapy and Aging on Cognition: Evidence for Executive Dysfunction

ABSTRACT The present study was designed to explore whether the frontal lobe hypothesis of cognitive aging may be extended to describe the cognitive effects associated with estrogen use in postmenopausal women. Postmenopausal estrogen-only users, estrogen + progesterone users, and non-users (60–80 years old), as well as young, regularly cycling women (18–30 years old) completed an item and source memory task. Since source memory is thought to rely more on executive processes than item memory, we hypothesized that aging and estrogen effects would be greater for source memory than for item memory. Neuropsychological tests explored whether the effects of aging and estrogen use were revealed on other tests of frontal lobe function. Results from the experimental task revealed greater aging and estrogen effects for source memory than for item memory, and neuropsychological results revealed aging and estrogen effects on a subset of tests of executive function. Women on estrogen + progesterone therapy did not outperform non-users, suggesting that the addition of progesterone to hormone therapy may mitigate the benefits induced by estrogen use alone. Overall, findings support the hypothesis that estrogen use may temper age-related cognitive decline by helping to maintain functions subserved by the frontal lobes.

Use it or lose it? SES mitigates age-related decline in a recency/recognition task

An important goal of aging research is to determine factors leading to individual differences that might compensate for some of the deleterious effects of aging on cognition. To determine whether socio-economic status (SES) plays a role in mitigating age-related decrements in the recollection of contextual details, we categorized older participants into low- and high-SES groups. Event-related potentials (ERPs) and behavioral data were recorded in a picture memory task involving recency and recognition judgments. Young, old-low and old-high SES groups did not differ in recognition performance. However, on recency judgments, old-low subjects performed at chance, whereas old-high subjects did not differ significantly from young adults. Consistent with their preserved recency performance, a long-duration frontal negativity was significantly larger for recency compared to recognition trials in the ERPs of the old-high SES group only. These data suggest that older adults with higher SES levels can use strategies to compensate for the adverse effects of aging in complex source memory tasks by recruiting additional neural resources apparently not required by the young.

Age Effects on the Neural Correlates of Episodic Retrieval: Increased Cortical Recruitment with Matched Performance

Functional neuroimaging investigations have revealed a range of age-related differences in the neural correlates of episodic memory retrieval. Typically, whereas activity is reduced in older compared with younger adults in some regions, other regions are engaged exclusively, or to a greater extent, in older adults. It is unclear whether such differences merely represent the neural correlates of the lower levels of memory performance and impaired recollection typical of older adults. This issue was addressed in the present event-related functional magnetic resonance imaging study. The level of recollection was matched between groups of healthy younger and older adults for a subset of picture items in a source memory task by manipulating the number of study presentations. Contrasts of the activity elicited by old items attracting correct source judgments and correctly identified new items revealed that the 2 groups recruited many of the same brain regions. However, a striking pattern of age-related differences was also observed. In older adults, retrieval-related increases in activity were more widespread and of greater magnitude than in the young. Moreover, regions demonstrating retrieval-related decreases in activity were almost absent in the older participants. These findings suggest an age-related decline in the efficiency with which neural populations support cognitive function.

Prefrontal involvement in source memory: An electrophysiological investigation of accounts concerning confidence and accuracy

Although a prefrontal involvement in the memory domain is well-documented, the specific functions the frontal lobes have in episodic memory are still unclear. This study aimed to disentangle theoretical accounts of prefrontal involvement concerning objective characteristics of the retrieval (i.e., accuracy) and accounts based on subjective features (i.e., confidence). Event-related potentials (ERPs) were recorded during the test phase of a source memory task in two experiments. The task was to retrieve the word and the voice of the speaker at study (experiment 1) or the voice of the speaker together with confidence ratings about the source judgment (experiment 2). ERPs in both experiments were not modulated by the success of the voice retrieval, discarding accounts linked to the retrieval success. A right-more-than-left late prefrontal positivity was found in both experiments. Moreover, in experiment 2, waves were more positive for low- than for high-confidence responses. This pattern was observed earlier over lateral parietal scalp regions and later, and more sustained in time, over anterior prefrontal regions. The dissociable effects found within the prefrontal scalp regions, specifically along the anterior–posterior and right–left dimensions, are interpreted as markers of qualitatively different monitoring processes.

Source and Item Memory for Odors and Objects in Children and Young Adults

Recall and recognition memory for odors are poorer in children than in adolescents. In addition, children perform worse than young adults on source memory tasks using visual and auditory stimuli. However, source memory for odor stimuli has not been examined in children. This study investigated source and item memory for odors and objects in children (7–10 years old) and young adults (18–24 years old). During the study phase, 1 male and 1 female experimenter (sources) randomly presented either 16 odors or 16 objects to the participant. Presentation alternated between sources so that each source presented 8 stimuli. Once the 16 stimuli were presented, the sources exited and a third experimenter began the test phase. To assess item recognition memory, a stimulus from the study phase and a novel stimulus were presented to the participant who was asked to choose the stimulus presented during the study phase. Source memory was assessed with the 8 stimuli from the study phase not used in the item memory task. The experimenter presented a stimulus and asked whether the male or female experimenter had presented the stimulus during the study phase. Results indicate that difference scores between item and source memory for odors were significantly larger for children than for young adults, indicating poorer source memory for children than adults. Difference scores for objects did not distinguish between groups. It has been suggested that the frontal lobes play a critical role in source memory and odor memory—a brain region that continues to develop into adolescence. Poor performance among children on the source memory task for odors may be due in part to immaturity of the frontal lobes.

The contribution of metamemory deficits to schizophrenia.

A number of recent studies have demonstrated that individuals with schizophrenia display knowledge corruption; that is, they hold false information with strong conviction. This aberration in metamemory is thought to stem from poor memory accuracy in conjunction with impaired discrimination of correct and incorrect judgments in terms of confidence. Thirty-one participants with schizophrenia, along with 61 healthy control participants and 48 control participants with other psychiatric conditions, participated in a computerized source memory task. Whereas no differences in memory accuracy were observed between the group with schizophrenia and the group with other psychiatric diagnoses, knowledge corruption was specifically impaired in those with schizophrenia. Schizophrenia participants showed a significantly decreased confidence gap: They were more confident in errors and less confident in correct responses relative to those in the control groups. Knowledge corruption is theorized to be a potential risk factor for the emergence of delusions.

The generation and resemblance heuristics in face recognition: Cooperation and competition.

Like all probabilistic decisions, recognition memory judgments are based on inferences about the strength and quality of stimulus familiarity. In recent articles, B. W. A. Whittlesea and J. Leboe (2000; J. Leboe & B. W. A. Whittlesea, 2002) proposed that such memory decisions entail various heuristics, similar to well-known heuristics in overt decision making. Using verbal stimulus materials, Whittlesea and Leboe illustrated 3 separate memory heuristics: fluency, generation, and resemblance. In the present investigation, the authors examined the generation and resemblance heuristics in face recognition. In 12 experiments, people memorized faces and later performed exclusion (source memory) tasks. Every experiment contained natural groups of facial photographs (e.g., Caucasian vs. Asian faces), but such groups were not always valid source-memory predictors. Instead, across experiments, the potential utility of generation and resemblance strategies was systematically varied. People were quite sensitive to such variations, changing from one heuristic to another as needed. However, they also combined heuristics, both improving and damaging performance across conditions. The relevance of recognition decision heuristics to eyewitness memory is considered.

Investigation of metamemory dysfunctions in first-episode schizophrenia

A number of recent studies have suggested that schizophrenia patients share metamemory deficits, particularly, a decreased ability to distinguish between errors and correct responses in terms of response confidence (i.e., decreased confidence gap): patients are over-confident in errors while at the same time being under-confident in responses that are in fact correct. This, along with increased error rates, leads to an inflation of inaccurate but confidently held memories, which has been termed knowledge corruption. Previous studies on metamemory in schizophrenia patients predominantly tested chronic patients, leaving open the possibility that metamemory deficits stem partly from increased chronicity and long-term treatment. The primary aim of the current study was to establish whether a decreased confidence gap is also detectable in first-episode schizophrenia. For this purpose, a source memory task was administered to 30 first-episode patients with a diagnosis of schizophrenia or schizophreniform disorder, and 15 healthy control subjects. During encoding, items were read aloud by the experimenter and the participant in alternating order. For the recognition phase, participants were required to state the source of the item, and their confidence in their response. In agreement with previous studies, the patients displayed a decreased confidence gap, and increased knowledge corruption relative to controls. A reduced distinction between correct and incorrect information in metacognition is proposed to be a vulnerability factor for the development of delusions in schizophrenia.

A check on the memory deficit hypothesis of obsessive–compulsive checking

A number of recent studies have challenged the hypothesis that patients with obsessive-compulsive disorder (OCD) display global memory deficits. An alleviated form of the memory deficit hypothesis posits that OCD patients share deficits to vividly recall memory episodes. According to the latter view, checking rituals can be understood as counter-productive coping strategies to "enrich" memory episodes in order to make them more distinctive. A source memory task was administered to 27 OCD (17 checkers) and 51 healthy participants. Along with confidence judgments, a remember-know procedure was employed to assess whether OCD patients display problems with conscious/vivid recollection. Patients with or without checking compulsions did not exhibit differences to controls on source memory accuracy and meta-memory. Patients forgot more self-generated items, which, however, was related to comorbid depressive but not OCD symptoms. Findings challenge the ubiquity of memory deficits in OCD. To account for the inconclusive pattern of results in the literature, it is suggested that patients mistrust their memories and adopt checking rituals only when perceived responsibility is inflated.

Source Memory in Children With Autism Spectrum Disorders

The evidence to date regarding memory processes in children with autism spectrum disorders (ASD) remains equivocal. Although children with these neurodevelopmental disorders have been shown to display exceptional memories for fact-based information, they seem to be less able to attach meaning or context to their memories. Thus, this study investigated the specific role of source memory in autism. Children with ASD were compared to a chronological and mental age-matched comparison group of typically developing children. Although children with autism performed similarly to controls on a fact recognition measure, their performance on a source memory task was significantly lower. The findings indicated, however, that the nature of source memory confusion in children with autism does not appear to reflect a generalized deficit in attaching context to memories but rather is dependent on the specific to-be-remembered information that, in this study, involves social aspects of context.

The relation between source memory and episodic memory: Comment on Siedlecki et al. (2005).

On the basis of an interesting structural equation analysis, K. L. Siedlecki, T. A. Salthouse, and D. E. Berish argued that "it may not be meaningful to refer to source memory as a construct distinct from episodic memory" (p. 31). This commentary highlights that this same point could also be made on conceptual grounds. To suggest that source and episodic memory are distinct concepts would confound tasks with theoretical constructs. All episodic tasks involve making attributions about the origin of mental experiences (source monitoring). Conversely, source memory tasks are designed to investigate episodic memory. No task is special, but each may be useful, depending on the focus of interest.

A model of verbal memory impairments in schizophrenia: two systems and their associations with underlying cognitive processes and clinical symptoms

In a broad cognitive study of schizophrenia we investigated the relationships of verbal memory impairments with cognitive underpinnings on the one hand, and clinical symptomatology on the other. The results have been reported in previous papers. In this paper we show how all these data could be integrated into a consistent pattern of associations. Fifty schizophrenic patients underwent a cognitive battery including a verbal memory task with free recall and recognition, a source memory task, and tests of processing speed and selective attention. Ratings for positive, negative and depressive symptoms were available for 40 of the patients. A factorial analysis revealed a distinction between measures of memory efficiency and measures of memory errors. The system of memory efficiency was associated with processing speed and selective attention at the cognitive level, and with depression at the symptom level. The system of memory errors was assumed to be underlain by source-monitoring deficits. These memory errors were increased by positive symptoms and decreased by certain negative symptoms. All the measures drawn from various memory tasks could be integrated into a model describing their associations with cognitive underpinnings and clinical symptomatology. This model provides a heuristic for the cognitive and pharmacological treatments of verbal memory impairments in schizophrenia, as well as for the understanding of positive symptoms.

Long-term effects of ketamine: evidence for a persisting impairment of source memory in recreational users

Rationale: Ketamine is an N-methyl- d-aspartate (NMDA)-receptor antagonist that is increasingly being used as a recreational drug. Previous research has shown gross generalised verbal memory impairments persisting 3 days after ketamine use in chronic users, however episodic memory has not specifically investigated in this population. Objective: To determine whether ketamine, on the night of drug use (day 0) and 3 days later, is associated with impaired episodic memory as assessed by a source memory task. Methods: Twenty ketamine users and 20 poly-drug controls were compared on a source memory task both on day 0 and 3. Participants also completed questionnaires on both days indexing schizophrenic-like and dissociative symptoms. Results: On day 0, ketamine abusers were impaired on both source memory and item recognition and scored more highly on schizophrenic and dissociative symptom scales compared to poly-drug controls. On day 3 ketamine abusers only displayed source memory impairments and these positively correlated with the level of schizophrenic-like symptoms on day 0. No differences on day 3 in schizophrenic-like or dissociative symptoms were observed. Conclusions: Ketamine abusers exhibit a persisting deficit in source memory on day 3 but not in item recognition. These findings suggest that repeated use of ketamine produces chronic impairments to episodic memory.

Long-term effects of ketamine: evidence for a persisting impairment of source memory in recreational users

Rationale: Ketamine is an N-methyl-d-aspartate (NMDA)-receptor antagonist that is increasingly being used as a recreational drug. Previous research has shown gross generalised verbal memory impairments persisting 3 days after ketamine use in chronic users, however episodic memory has not specifically investigated in this population. Objective: To determine whether ketamine, on the night of drug use (day 0) and 3 days later, is associated with impaired episodic memory as assessed by a source memory task. Methods: Twenty ketamine users and 20 poly-drug controls were compared on a source memory task both on day 0 and 3. Participants also completed questionnaires on both days indexing schizophrenic-like and dissociative symptoms. Results: On day 0, ketamine abusers were impaired on both source memory and item recognition and scored more highly on schizophrenic and dissociative symptom scales compared to poly-drug controls. On day 3 ketamine abusers only displayed source memory impairments and these positively correlated with the level of schizophrenic-like symptoms on day 0. No differences on day 3 in schizophrenic-like or dissociative symptoms were observed. Conclusions: Ketamine abusers exhibit a persisting deficit in source memory on day 3 but not in item recognition. These findings suggest that repeated use of ketamine produces chronic impairments to episodic memory.

The late posterior negativity in ERP studies of episodic memory: action monitoring and retrieval of attribute conjunctions

The focus of the present paper is a late posterior negative slow wave (LPN) that has frequently been reported in event-related potential (ERP) studies of memory. An overview of these studies suggests that two broad classes of experimental conditions tend to elicit this component: (a) item recognition tasks associated with enhanced action monitoring demands arising from response conflict and (b) memory tasks that require the binding of items with contextual information specifying the study episode. A combined stimulus- and response-locked analysis of data from two studies mapping onto these classes allowed a temporal and functional decomposition of the LPN. While only the LPN observed in the item recognition task could be attributed to the involvement of a posteriorly distributed response-locked error-related negativity (or error negativity; ERN/Ne) occurring immediately after the response, the source-memory task was associated with a stimulus-locked negative slow wave occurring prior and during response execution that was evident when data were matched for response latencies. We argue that the presence of the former reflects action monitoring due to high levels of response conflict, whereas the latter reflects retrieval processes that may act to reconstruct the prior study episode when task-relevant attribute conjunctions are not readily recovered or need continued evaluation.