Source memory and encoding strategy in normal aging

Modern scores for traditional tests - Review of the diagnostic potential of scores derived from word list learning tests in mild cognitive impairment and early Alzheimer's Disease

Episodic memory impairment is one of the early hallmarks in Alzheimer's Disease. In the clinical diagnosis and research, episodic memory impairment is typically assessed using word lists that are repeatedly presented to and recalled by the participant across several trials. Until recently, total learning scores, which consist of the total number of words that are recalled by participants, were almost exclusively used for diagnostic purposes. The present review aims at summarizing evidence on additional scores derived from the learning trials which have recently been investigated more frequently regarding their diagnostic potential. These scores reflect item acquisition, error frequencies, strategy use, intertrial fluctuations, and recall consistency. Evidence was summarized regarding the effects of clinical status on these scores. Preclinical, mild cognitive impairment and mild Alzheimer's Disease stages were associated with a pattern of reduced item acquisition, more errors, less strategy use, and reduced access of items, indicating slowed and erroneous encoding. Practical implications and limitations of the present research will be discussed.

Semantic Clustering during Verbal Episodic Memory Encoding and Retrieval in Older Adults: One Cognitive Mechanism of Superaging

Normal aging is commonly accompanied by a decline in cognitive abilities, including memory, yet some individuals maintain these abilities as they get older. We hypothesize that semantic clustering, as an effective strategy for improving performance on episodic recall tasks, may contribute to the maintenance of youthful memory in older adults. We investigated the dynamics of spontaneous production and utilization of the semantic clustering strategy in two independent samples of older adults who completed a list learning paradigm (N1 = 40 and N2 = 29, respectively). Specifically, we predicted and observed that older adults who spontaneously used a semantic clustering strategy throughout the encoding process learned more words by the culmination of the encoding trials (Sample 1, R2= 0.53, p < 0.001; Sample 2, R2= 0.51, p < 0.001), and that those who utilized this strategy during retrieval recalled more words, when compared to older adults who did not produce or utilize a semantic clustering strategy during both a short (Sample 1, R2 = 0.81, p < 0.001; Sample 2, R2 = 0.70, p < 0.001) and long delay retrieval (Sample 1, R2 = 0.83, p < 0.001; Sample 2, R2 = 0.77, p < 0.001). We further predicted and observed that older adults who maintained a youthful level of delayed free recall (i.e., "Superagers") produced (Sample 1, F(1, 38) = 17.81, p < 0.0001; Sample 2, F(1, 27) = 14.45, p < 0.0001) and utilized (Sample 1, F(1, 39) = 25.84, p < 0.0001; Sample 2, F(1, 27) = 12.97, p < 0.01) more semantic clustering than did older individuals with normal memory for their age. These results suggest one cognitive mechanism through which Superagers maintain youthful memory function and raise the possibility that older adults may be able to train themselves to use strategies to promote better memory.

Strategy Use Mediates the Relation between Openness to Experience and Episodic Memory in Younger and Older Adults

Previous research has shown that people with higher levels of Openness to Experience show higher levels of cognitive functioning. However, the mechanisms underlying this personality-cognition relation are not well understood. The goal of the current project was to examine whether strategy use mediates the relation between Openness to experience and retrospective memory, and whether the role of strategy use in the Openness-memory relation was the same in younger and older adults.

METHOD

Two studies were conducted. In each of them, younger and older adults were administered a retrospective memory task (29 younger and 27 older in Study 1, 43 adults of all ages in Study 2). They were asked to report the strategies they used during the task, and to complete an Openness to Experience scale.

RESULTS

Consistent with previous reports, higher scores of Openness to experience and greater use of efficient memory strategies were associated with higher levels of memory performance. In addition, individual differences in memory strategy use mostly mediated the relation between Openness and memory performance. Results did not support a mediation model moderated by age. That is, the role of memory strategy use in the relation between Openness and memory was the same in younger and older adults.

CONCLUSION

Higher levels of Openness are associated with better memory performance, mostly because people with higher levels of Openness use more efficient memory strategies.

Factors related to memory absence and delusional memories in patients in intensive care units managed with light sedation

OBJECTIVES

Currently, light sedation is typically given to patients in intensive care units and studies have not extensively examined the factors related to absences or abnormalities of their memories. We, therefore, analysed the factors related to the absence/abnormalities of patients' memories in intensive care units.

RESEARCH METHODOLOGY

A secondary analysis of previously collected survey data examining patients' experiences in an intensive care unit was undertaken (n = 405; women = 38%; median age = 70 years). To observe absent or distorted memories, patients were interviewed after leaving the intensive care unit. We analysed key factors through content analysis of the interviews and field notes.

SETTING

The intensive care unit of a university hospital.

MAIN OUTCOME MEASURE

Patients' absent or distorted memories after leaving the intensive care unit.

RESULTS

Half the patients reported an absence of memories. This was associated with old age and with longer duration of mechanical ventilation. Absent or fragmentary memories were not distressing. Fragmentary and fearful intensive care unit memories were associated with being older. Delusional memories, some of which reflected actual events, were present in 3% of patients.

CONCLUSION

Absence of memories were not distressing, delusional memories occurred less and these memories could comprise of an event in ICU that is difficult for patients to understand.

Strategy use and verbal memory in older adults: The role of intellectual functioning and the preferential impact of semantic clustering

Objective: The relative importance of various mechanisms supporting declarative verbal memory among older adults remains uncertain. The present study examined the impact of strategy use (specifically semantic clustering) versus other variables known to impact memory performance (age, sex, education, FSIQ, processing speed, and executive functioning) on verbal memory functioning among healthy older adults.Methods: Healthy older adults from the California Verbal Learning Test, Second Edition standardization sample were selected (N = 242). Relationships between verbal memory, demographics variables, and neuropsychological factors were established, and a hierarchical regression analysis was conducted to examine the individual contributions of these variables in predicting memory performance.Results: Bivariate correlations suggested that memory was significantly related to demographic factors, IQ, executive functioning, and semantic clustering. Importantly, hierarchical regression analysis revealed that semantic clustering significantly and independently contributed to recall performance beyond the demonstrated impacts of FSIQ, speed, executive functioning, and demographic variables. Furthermore, FSIQ did not moderate the relationship between semantic clustering and memory indicating that this strategy is an important factor in bolstering recall, independent of FSIQ.Conclusions: Our results highlight the critical importance of semantic clustering utilization in enhancing memory performance among healthy older adults.

Differences in Semantic Memory Encoding Strategies in Young, Healthy Old and MCI Patients

Associative processes, such as the encoding of associations between words in a list, can enhance episodic memory performance and are thought to deteriorate with age. Here, we examine the nature of age-related deficits in the encoding of associations, by using a free recall paradigm with visual arrays of objects. Fifty-five participants (26 young students; 20 cognitive healthy older adults; nine patients with Mild Cognitive Impairment, MCI) were shown multiple slides (experimental trials), each containing an array of nine common objects for recall. Most of the arrays contained three objects from three semantic categories, each. In the remaining arrays, the nine objects were unrelated. Eye fixations were also monitored during the viewing of the arrays, in a subset of the participants. While for young participants the immediate recall was higher for the semantically related arrays, this effect was diminished in healthy elderly and totally absent in MCI patients. Furthermore, only in the young group did the sequence of eye fixations show a semantic scanning pattern during encoding, even when the related objects were non- adjacent in the array. Healthy elderly and MCI patients were not influenced by the semantic relatedness of items during the array encoding, to the same extent as young subjects, as observed by a lack of (or reduced) semantic scanning. The results support a version of the encoding of the association aging-deficit hypothesis.

Differential Effects of Valence and Encoding Strategy on Internal Source Memory and Judgments of Source: Exploring the Production and the Self-Reference Effect

Item memory studies show that emotional stimuli are associated with improved memory performance compared to neutral ones. However, emotion-related effects on source memory are less consistent. The current study probed how emotional valence and specific encoding conditions influence internal source memory performance and judgments of source (JOSs). In two independent experiments, participants were required to read silently/aloud (Experiment 1) or to perform self-reference/common judgments (Experiment 2) on a list of negative/neutral/positive words. They also performed immediate JOSs ratings for each word. The study phase was followed by a test phase in which participants performed old-new judgments. In Experiment 1, the production effect was replicated for item memory, but the effects of valence on item and source memory were not significant. In Experiment 2, self-referential processing effects on item and source memory differed as a function of valence. In both experiments, JOSs ratings were sensitive to valence and encoding conditions, although they were not predictive of objective memory performance. These findings demonstrate that the effects of valence on internal source memory and JOSs are modulated by encoding strategy. Thus, the way information is encoded can shed light on how emotion might enhance, impair or exert no influence on source memory.

Elaboration Benefits Source Memory Encoding Through Centrality Change

Variations in levels of processing affect memory encoding and subsequent retrieval performance, but it is unknown how processing depth affects communication patterns within the network of interconnected brain regions involved in episodic memory encoding. In 113 healthy adults scanned with functional MRI, we used graph theory to calculate centrality indices representing the brain regions’ relative importance in the memory network. We tested how communication patterns in 42 brain regions involved in episodic memory encoding changed as a function of processing depth, and how these changes were related to episodic memory ability. Centrality changes in right middle frontal gyrus, right inferior parietal lobule and left superior frontal gyrus were positively related to semantic elaboration during encoding. In the same regions, centrality during successful episodic memory encoding was related to performance on the episodic memory task, indicating that these centrality changes reflect processes that support memory encoding through deep elaborative processing. Similar analyses were performed for congruent trials, i.e. events that fit into existing knowledge structures, but no relationship between centrality changes and congruity were found. The results demonstrate that while elaboration and congruity have similar beneficial effects on source memory performance, the cortical signatures of these processes are probably not identical.

East-West cultural differences in encoding objects in imagined social contexts

It has been shown in literature that East Asians are more inclined to process context information than individuals in Western cultures. Using a context memory task that requires studying object images in social contexts (i.e., rating objects in an imagined social or experiential scenario), our recent study revealed an age-invariant advantage for Chinese young and older participants compared to their Canadian counterparts in memory for encoding contexts. To examine whether this cultural difference also occurred during encoding, this follow-up report analyzed encoding performance and its relationship to subsequent memory based on the same data from the same task of the same sample. The results revealed that at encoding, Chinese participants provided higher ratings of objects, took longer to rate, and reported more vivid imagery of encoding contexts relative to their Canadian counterparts. Furthermore, only Chinese participants rated objects with recognized context at retrieval higher and slower relative to those with misrecognized context. For Chinese participants, primarily older adults, slower ratings were only related to better context memory but not item memory. Importantly, Chinese participants' context memory advantage disappeared after controlling for encoding differences. Taken together, these results suggest that Chinese participants' memory advantage for social contexts may have its origin in the construction of elaborative and meaningful object-context associations at encoding.

Age- and performance-related differences in encoding during early childhood: insights from event-related potentials

Previous studies have found that children show rapid and significant improvements in their ability to remember individual items and the contextual details that surround these items (i.e., episodic memory) during early childhood. Encoding processes have been suggested to contribute to the development of episodic memory; however, few studies have investigated encoding processes. The goal of the current study was to examine age- and performance-related effects on encoding in children between 4 and 8 years of age using event-related potentials (ERPs). Results revealed effects of both age and performance on encoding, as indexed by the ERPs response. However, the nature of these effects differed between subsequent recognition and subsequent recollection, as well as for the two ERP components (i.e., Nc and LSW) examined. These findings are important as they contribute empirical evidence that encoding processes show developmental change across early childhood. In addition, these findings highlight the importance of controlling for performance differences in future studies examining developmental changes in episodic memory.

Age and active navigation effects on episodic memory: A virtual reality study

We investigated the navigation-related age effects on learning, proactive interference semantic clustering, recognition hits, and false recognitions in a naturalistic situation using a virtual apartment-based task. We also examined the neuropsychological correlates (executive functioning [EF] and episodic memory) of navigation-related age effects on memory. Younger and older adults either actively navigated or passively followed the computer-guided tour of an apartment. The results indicated that active navigation increased recognition hits compared with passive navigation, but it did not influence other memory measures (learning, proactive interference, and semantic clustering) to a similar extent in either age group. Furthermore, active navigation helped to reduce false recognitions in younger adults but increased those made by older adults. This differential effect of active navigation for younger and older adults was accounted for by EF score. Like for the subject-performed task effects, the effects from the navigation manipulation were well accounted for by item-specific/relational processing distinction, and they were also consistent with a source monitoring deficit in older adults.

Dissociating the effects of semantic grouping and rehearsal strategies on event-related brain potentials

The application of elaborative encoding strategies during learning, such as grouping items on similar semantic categories, increases the likelihood of later recall. Previous studies have suggested that stimuli that encourage semantic grouping strategies had modulating effects on specific ERP components. However, these studies did not differentiate between ERP activation patterns evoked by elaborative working memory strategies like semantic grouping and more simple strategies like rote rehearsal. Identification of neurocognitive correlates underlying successful use of elaborative strategies is important to understand better why certain populations, like children or elderly people, have problems applying such strategies. To compare ERP activation during the application of elaborative versus more simple strategies subjects had to encode either four semantically related or unrelated pictures by respectively applying a semantic category grouping or a simple rehearsal strategy. Another goal was to investigate if maintenance of semantically grouped vs. ungrouped pictures modulated ERP-slow waves differently. At the behavioral level there was only a semantic grouping benefit in terms of faster responding on correct rejections (i.e. when the memory probe stimulus was not part of the memory set). At the neural level, during encoding semantic grouping only had a modest specific modulatory effect on a fronto-central Late Positive Component (LPC), emerging around 650 ms. Other ERP components (i.e. P200, N400 and a second Late Positive Component) that had been earlier related to semantic grouping encoding processes now showed stronger modulation by rehearsal than by semantic grouping. During maintenance semantic grouping had specific modulatory effects on left and right frontal slow wave activity. These results stress the importance of careful control of strategy use when investigating the neural correlates of elaborative encoding.

Cognitive neurorehabilitation of HIV-associated neurocognitive disorders: a qualitative review and call to action

Despite significant advances in the virologic management of HIV infection over the last two decades, effective treatments for HIV-associated neurocognitive disorders (HAND) remain elusive. While pharmacological interventions have yielded some success in improving neurocognitive outcomes in HIV, there is a dearth of rigorous studies examining the efficacy of cognitive rehabilitation for remediating HIV-associated neurocognitive impairment. This qualitative review summarizes and critiques the emerging literature on cognitive and behavioral treatments for HAND, which provides many reasons for optimism, but also has major limitations that underscore the scope of the work that lies ahead. Considering the notable real-world consequences of HAND, the development, validation, and clinical deployment of cognitive neurorehabilitation interventions tailored to the needs of persons living with HIV infection is a priority for clinical neuroAIDS investigators. In describing potential future directions for this endeavor, particular attention was paid to the application of cognitive neuropsychological principles in developing theory-driven approaches to managing HAND, improving everyday functioning, and enhancing HIV health outcomes.

A Reexamination of Source Monitoring Deficits in the Elderly: Evidence for Independent Age Deficits of Item and Source Memory

Within the experimental literature there is substantial evidence of larger age-related deficits in retrieving source information relative to item-based information. However, this evidence is potentially subject to methodological criticism given that several studies have argued for the presence of source-monitoring deficits by examining source memory contingent on correct recall of item information but not the reverse. In order to address this potential shortcoming our study examines recall of both item information contingent on correct source judgement and source-based information contingent on correct recall of item information. We demonstrate that when this novel type of analysis is conducted, there are age deficits for both source and item information, and no evidence of a selectively greater source-monitoring deficit in the elderly. The results are discussed with reference to two overarching theoretical positions concerning age-related deficits in memory performance.

Spontaneous strategy use protects against visual working memory deficits in older adults infected with HIV

Recent studies suggest that older human immunodeficiency virus (HIV)-infected adults are at particular risk for HIV-associated neurocognitive disorders (HAND), including dementia. Deficits in attention/working memory are posited to play a central role in the development of HAND among older adults. The aim of the present study was to examine the possible protective benefits of spontaneous strategy use during a visual working memory task in 46 older and 42 younger adults infected with HIV. Results revealed a significant interaction between age and strategy use, with older adults who used a meta-cognitive strategy demonstrating superior working memory performance versus non-strategy users. This effect was not observed in the younger HIV-infected sample and was not better explained by possible confounding factors, such as education, comorbid medical conditions, or HIV disease severity. Within the older group, strategy use was associated with better executive functions and higher estimated verbal intelligence. Findings from this study suggest that working memory declines in older HIV-infected adults are moderated by the use of higher-level mnemonic strategies and may inform cognitive neurorehabilitation efforts to improve cognitive and everyday functioning outcomes in older persons living with HIV infection.

Improved cognitive-cerebral function in older adults with chromium supplementation

Insulin resistance is implicated in the pathophysiological changes associated with Alzheimer's disease, and pharmaceutical treatments that overcome insulin resistance improve memory function in subjects with mild cognitive impairment (MCI) and early Alzheimer's disease. Chromium (Cr) supplementation improves glucose disposal in patients with insulin resistance and diabetes. We sought to assess whether supplementation with Cr might improve memory and neural function in older adults with cognitive decline. In a placebo-controlled, double-blind trial, we randomly assigned 26 older adults to receive either chromium picolinate (CrPic) or placebo for 12 weeks. Memory and depression were assessed prior to treatment initiation and during the final week of treatment. We also performed functional magnetic resonance imaging (fMRI) scans on a subset of subjects. Although learning rate and retention were not enhanced by CrPic supplementation, we observed reduced semantic interference on learning, recall, and recognition memory tasks. In addition, fMRI indicated comparatively increased activation for the CrPic subjects in right thalamic, right temporal, right posterior parietal, and bifrontal regions. These findings suggest that supplementation with CrPic can enhance cognitive inhibitory control and cerebral function in older adults at risk for neurodegeneration.

HIV-associated episodic memory impairment: evidence of a possible differential deficit in source memory for complex visual stimuli

HIV infection is often associated with frontal systems pathology and related deficits in the strategic encoding and retrieval aspects of episodic memory. However, no prior HIV studies have explicitly examined source memory, which refers to recall of information regarding the context in which a declarative memory was formed. Source memory is heavily reliant on frontal systems and strategic cognitive processes and is singly dissociable from the content of the memory (i.e., item memory), which is more dependent on medial temporal systems and automatic processes. The present study examined item and source memory in 60 individuals with HIV infection and 35 demographically similar seronegative participants. The primary finding of interest was a significant HIV effect on source (but not item) memory for complex visual stimuli. Follow-up correlational analyses showed a significant association between visual source memory errors and impairment on measures of executive functions, working memory, and higher-level list learning encoding strategies. These findings extend the hypothesized profile of strategic encoding and retrieval deficits in HIV to the construct of source memory, which may be differentially affected relative to item memory for complex visual stimuli.

Aging and semantic cueing during learning and retention of verbal episodic information

The purpose of this study was to determine the effectiveness of semantic cues provided at encoding and during retention for older adults' memory. For the California Verbal Learning Test-II, participants received semantic or nonsemantic cues that were varied across groups at encoding and during the retention interval. Provision of a semantic cue at encoding led to greater semantic clustering at learning, but not increased recall performance. Providing a semantic cue during the retention interval led to better delayed free recall and greater semantic clustering. No group differences in recall or semantic clustering were found at delayed cued recall. The current findings suggest that semantic cues can be beneficial for recalling unstructured information when administered during the retention interval.

Neuroanatomical and cognitive mediators of age-related differences in episodic memory

Aging is associated with declines in episodic memory. In this study, the authors used a path analysis framework to explore the mediating role of differences in brain structure, executive functions, and processing speed in age-related differences in episodic memory. Measures of regional brain volume (prefrontal gray and white matter, caudate, hippocampus, visual cortex), executive functions (working memory, inhibitory control, task switching, temporal processing), processing speed, and episodic memory were obtained in a sample of young and older adults. As expected, age was linked to reduction in regional brain volumes and cognitive performance. Moreover, neural and cognitive factors completely mediated age differences in episodic memory. Whereas hippocampal shrinkage directly affected episodic memory, prefrontal volumetric reductions influenced episodic memory via limitations in working memory and inhibitory control. Age-related slowing predicted reduced efficiency in temporal processing, working memory, and inhibitory control. Lastly, poorer temporal processing directly affected episodic memory. No direct effects of age on episodic memory remained once these factors were taken into account. These analyses highlight the value of a multivariate approach with the understanding of complex relationships in cognitive and brain aging.

Conceptual and perceptual similarity between encoding and retrieval contexts and recognition memory context effects in older and younger adults

We examined the hypothesis that older adults' deficits in contextual memory result from difficulties in contending with partial encoding-to-retrieval changes in the context. We measured effects of contextual change and constancy on recognition memory for words, in older and younger adults. We assessed the ability to adjust to partial contextual changes by manipulating encoding-retrieval context similarity: identical, new and unrelated, conceptually similar, or perceptually similar. For both older and younger adults, identical and conceptually similar contexts benefited recognition of target words, whereas perceptually similar contexts did not. Older adults did not make more false alarms. In contrast, older adults' direct recognition of contextual stimuli was at chance. These results indicate that retrieval processes, rather than encoding or rigidity in the use of contextual cues, are implicated in older adults' difficulties in memory for contextual information.

Effects of hormone replacement therapy and aging on cognition: evidence for executive dysfunction

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.

Differential Course of Executive Control Changes During Normal Aging

Normal aging has been associated with executive control deficits, but it is as yet unclear whether different executive subprocesses are differentially affected during the course of aging. The present study aimed to investigate age effects on a range of executive control subcomponents. Four consecutive age groups (20-30 years, 31-45 years, 46-60 years, 61-75 years), matched on present state IQ and mood, were compared on tasks of strategic memory processing, verbal fluency, reasoning, inhibition, task management, and self-rating of executive abilities. Deficits concerning the suppression of habitual and experimentally induced prepotent response tendencies and the ability to efficiently divide attention were observed in subjects over 60 years of age compared to the younger groups, while memory, verbal fluency, and reasoning were largely unaffected. Results suggest a sharp decline of executive function after age 60 and a differential course of different executive subcomponents across aging, adding further support to a multi-dimensional model of executive function.

An fMRI investigation of short-term source memory in young and older adults

Using functional magnetic resonance imaging (fMRI) and a working memory procedure, we compared source memory judgments (format and location) with old-new judgments in young and older adults. Consistent with previous fMRI findings, for young adults, an area of left dorsolateral prefrontal cortex showed greater activity during format than old-new judgments made immediately, as well as those made after a brief, filled delay. In contrast, for older adults, activity in this area was not greater during format than old-new judgments at either retention interval. These data provide additional evidence that left lateral prefrontal cortex is important in monitoring specific source information and new evidence that older adults' source memory deficits may be related, in part, to reduced function of this brain area.

Memory for temporal context: Effects of ageing, encoding instructions, and retrieval strategies

Young and older adults were compared on a list discrimination task. In Experiment 1, performance declined with ageing after incidental and intentional encoding of the temporal context. Moreover, there was no benefit for intentional encoding in either group. In Experiment 2, each list was associated with a different encoding context. There were age differences in performance when participants tried to retrieve the encoding context of the items as a cue for their list of occurrence, but not when participants evaluated temporal distance from the strength of the memory trace. This suggests that the age-related decrease in list discrimination could be at least partly due to a difficulty in inferring strategically the temporal context of the items from information encoded in the same time.

Discomfort and factual recollection in intensive care unit patients

INTRODUCTION

A stay in the intensive care unit (ICU), although potentially life-saving, may cause considerable discomfort to patients. However, retrospective assessment of discomfort is difficult because recollection of stressful events may be impaired by sedation and severe illness during the ICU stay. This study addresses the following questions. What is the incidence of discomfort reported by patients recently discharged from an ICU? What were the sources of discomfort reported? What was the degree of factual recollection during patients' stay in the ICU? Finally, was discomfort reported more often in patients with good factual recollection?

METHODS

All ICU patients older than 18 years who had needed prolonged (>24 hour) admission with tracheal intubation and mechanical ventilation were consecutively included. Within three days after discharge from the ICU, a structured, in-person interview was conducted with each individual patient. All patients were asked to complete a questionnaire consisting of 14 questions specifically concerning the environment of the ICU they had stayed in. Furthermore, they were asked whether they remembered any discomfort during their stay; if they did then they were asked to specify which sources of discomfort they could recall. A reference group of surgical ward patients, matched by sex and age to the ICU group, was studied to validate the questionnaire.

RESULTS

A total of 125 patients discharged from the ICU were included in this study. Data for 123 ICU patients and 48 surgical ward patients were analyzed. The prevalence of recollection of any type of discomfort in the ICU patients was 54% (n = 66). These 66 patients were asked to identify the sources of discomfort, and presence of an endotracheal tube, hallucinations and medical activities were identified as such sources. The median (min-max) score for factual recollection in the ICU patients was 15 (0-28). The median (min-max) score for factual recollection in the reference group was 25 (19-28). Analysis revealed that discomfort was positively related to factual recollection (odds ratio 1.1; P < 0.001), especially discomfort caused by the presence of an endotracheal tube, medical activities and noise. Hallucinations were reported more often with increasing age. Pain as a source of discomfort was predominantly reported by younger patients.

CONCLUSION

Among postdischarge ICU patients, 54% recalled discomfort. However, memory was often impaired: the median factual recollection score of ICU patients was significantly lower than that of matched control patients. The presence of an endotracheal tube, hallucinations and medical activities were most frequently reported as sources of discomfort. Patients with a higher factual recollection score were at greater risk for remembering the stressful presence of an endotracheal tube, medical activities and noise. Younger patients were more likely to report pain as a source of discomfort.

Preserved spatial memory over brief intervals in older adults

Two studies compared young and older adults' memory for location information after brief intervals. Experiment 1 found that accuracy of intentional spatial memory for individual locations was similar in young and older participants for set sizes of 3 and 6. Both groups also encoded individual locations in relation to the larger configuration of locations. Experiment 2 showed that like young adults, older adults' latency to respond to a test probe in a letter working memory task was negatively influenced by spatial information that was irrelevant to the task. This interference effect indicated preserved incidental memory for spatial information in older adults. Together, these data suggest that initial encoding of spatial information for relatively small numbers of items is largely preserved in healthy older adults and that representations of spatial information persist over short intervals.

The effects of aging on location-based and distance-based processes in memory for time

Retrieving when an event occurred may depend on an estimation of the age of the event (distance-based processes) or on strategic reconstruction processes based on contextual information associated with the event (location-based processes). Young and older participants performed a list discrimination task that has been designed to dissociate the contribution of both types of processes. An adapted Remember/Know/Guess procedure [Can. J. Exp. Psychol. 50 (1996) 114] was developed to evaluate the processes used by the participants to recognize the stimuli and retrieve their list of occurrence. The results showed that aging disrupts location-based processes more than distance-based processes. In addition, a limitation of speed of processing and working-memory capacities was the main predictor of age-related differences on location-based processes, whereas working-memory capacities mediated partly age differences on distance-based processes.

Cognitive findings in spinocerebellar ataxia type 2: relationship to genetic and clinical variables

Several authors have recently reported a broad cognitive impairment in autosomal dominant cerebellar ataxias (ADCAs) patients. However, only a few studies on neuropsychological features in spinocerebellar ataxia type 2 (SCA2) patients are present in the current literature. The aim of this study is to evaluate the cognitive impairment in a wide sample of SCA2 patients and to verify the role of different disease-related factors (age of onset, disease duration, and clinical severity) on intellectual abilities. We administered a battery of neuropsychological tests assessing handedness, attention, short- and long-term verbal and visuo-spatial memory, executive functions, constructive abilities, general intellectual abilities and depression to 18 SCA2 patients belonging to eight families who came to our observation. Evidence of impaired verbal memory, executive functions and attention was found. The cognitive status was partially related to clinical severity rather than to disease duration or age at onset of symptoms. We partially confirmed data on cognitive defects already reported by others but we also found defective attention skills as well as significant lower performances in a nonverbal intelligence task.

Age-related changes in source memory retrieval: an ERP replication and extension

Event-related potentials (ERPs) were recorded (62 scalp sites) from young (M=22) and older (M=66) adults during tests of item recognition and source memory, in a replication and extension of a previous study [Psychol. Aging 14 (1999) 390-413]. Participants studied two temporally distinct lists of sentences (each with two unassociated nouns). At test, in response to studied and unstudied nouns, participants made old/new, followed by source (i.e., list) judgments. Several measures were employed to enhance the source memory performance of the older adults. These were successful, as the old adults showed source memory performance comparable to that of the young subjects from the previous study (67%). Nonetheless, the younger adults significantly outperformed the older adults on measures of item and source memory performance. The ERPs revealed that both age groups showed a robust early, posterior-maximal episodic memory (EM) effect. However, despite their enhanced source memory performance, the ERPs of the old failed to show a robust late, right-prefrontal EM effect, which was again present in the ERPs of the young. By contrast, the older adults showed a central negative component not seen in the ERPs of the young. These results are consistent with the frontal lobe deficit hypothesis of aging and provide some evidence that old and young may use distinct cortical networks during source memory retrieval.

Cerebral aging: neuropsychological, neuroradiological, and neurometabolic correlates

The aging process is associated with a progressive cognitive decline, but both the extent of this decline and the profile of age-related cognitive changes remain to be clearly established. Currently, cognitive deficits associated with aging may be diagnosed under the categories of age-associated memory impairment, age-associated cognitive impairment, or the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) category of age-related cognitive decline. Age-related decline has been reported for several cognitive domains, such as language (eg, verb naming, verbal fluency), visuospatial abilities (eg, facial discrimination), executive functions (eg, set shifting, problem solving), and memory functions (eg, declarative learning, source memory). There is an age-related decline in brain cortical volume, which primarily involves association cortices and limbic regions. Studies of brain metabolic activity demonstrate an age-related decline in neocortical areas. Activation studies using cognitive tasks demonstrate that older healthy individuals have a different pattern of activation from younger subjects, suggesting thai older subjects may recruit additional brain areas in order to maintain performance.