Memory span and long-term memory deficits in brain-impaired patients

Measures of verbal and visuospatial memory span and long-term memory were obtained from 21 brain-impaired and 21 neurologically unimpaired Veterans Administration medical patients. Significant deficits in both memory span and long-term memory were observed in the brain-impaired patients. Contrary to predictions from the experimental literature, memory span tests that require more processing of item content and location were not superior in detecting the memory span deficits. Discriminant function analyses revealed that measures of verbal and visuospatial long-term memory provided unique discrimination between the brain-impaired and unimpaired patients. However, when memory span measures were analyzed alone, inclusion of more than one measure of memory span did not provide additional unique discrimination. Implications for the clinical assessment of memory functioning are discussed.     

The role of the frontal lobes in memory: evidence from unilateral frontal resections for relief of intractable epilepsy.

The current investigation explored processes associated with memory deficits in patients with frontal lobe dysfunction. Specifically, we examined deficits associated with the encoding, consolidation, and retrieval of information in memory in 53 patients who underwent either a unilateral frontal (N=13) or temporal (N=40) lobe resection for relief of intractable epilepsy. Post-surgical memory scores indicated that the frontal group and the temporal group did not differ in consolidation of information, as defined by the information forgotten between immediate and delayed recall. Instead, the temporal group evidenced significantly poorer recall of verbal information at both immediate and delayed recall. This effect was especially strong in the left temporal group for the recall of verbal information. Although no group differences were observed in the degree to which patients semantically organized information or made recency discriminations, the frontal group exhibited significantly weaker release from proactive interference than the temporal group, suggesting some impairment in encoding and retrieval processes associated with frontal lobe dysfunction.     

Preliminary data on the effect of culture on the assessment of Alzheimer's disease-related verbal memory impairment with the International Shopping List Test

The International Shopping List Test (ISLT) is a measure of verbal learning and memory, developed specifically for use in people from different cultural and linguistic backgrounds. In this report, we describe two studies that examined the ISLT's ability to detect memory impairment and memory decline in patients with mild Alzheimer's disease (AD) from a range of cultural and linguistic backgrounds. In Study 1, the performance of Australian-English-speaking adults with mild AD was compared with that of native Australian-English- and Korean-speaking patients with mild AD. Compared with controls, patients with AD from both language groups showed large but equivalent impairments in total recall, delayed recall, rate of learning, and primacy and retention-weighted recall (RWR) measures on the ISLT. In Study 2, the rate of deterioration in verbal memory over 1 year was examined in groups of native Canadian-English, French, and Korean speakers with mild AD using the total recall, delayed recall, and RWR measures. Rates of change on all three measures were equivalent across the language groups, although the magnitude of deterioration was most pronounced for the total recall and RWR measures. Taken together, these results suggest that the ISLT is valid and reliable for the assessment of verbal learning and memory impairment and decline in patients with mild AD from diverse language groups.     

Patterns of subjective memory impairment in the elderly: association with memory performance

BACKGROUND: The association of subjective memory impairment (SMI) with cognitive performance in healthy elderly subjects is poor because of confounds such as depression. However, SMI is also a predictor for future dementia. Thus, there is a need to identify subtypes of SMI that are particularly related to inferior memory performance and may represent at-risk stages for cognitive decline.METHOD: A total of 2389 unimpaired subjects were recruited from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), as part of the German Competence Network on Dementia. Clusters of SMI according to patterns of response to SMI questions were identified. Gender, age, depressive symptoms, apolipoprotein E (apoE) genotype, delayed recall and verbal fluency were included in a Classification and Regression Tree (CART) analysis to identify discriminators between the clusters. RESULTS: We identified three clusters. Cluster 1 contained subjects without memory complaints. Cluster 2 contained subjects with general memory complaints, but mainly without memory complaints on individual tasks of daily living. Cluster 3 contained subjects with general memory complaints and complaints on individual tasks of daily living. Depressive symptoms, as the first-level discriminator, distinguished between clusters 1 and 2 versus cluster 3. In subjects with only a few depressive symptoms, delayed recall discriminated between cluster 1 versus clusters 2 and 3. CONCLUSIONS: In SMI subjects with only a minor number of depressive symptoms, memory complaints are associated with delayed recall. As delayed recall is a sensitive predictor for future cognitive decline, SMI may be the first manifestation of future dementia in elderly subjects without depression.     

Short-term forgetting: Comparisons between patients with dementia of the alzheimer type,depressed, and normal elderly

Group by retention interval interactions in previous studies of patients with dementia of the Alzheimer type (DAT) and normal elderly have been interpreted as evidence for more rapid rates of forgetting by DAT patients (Corkin, 1982; Moms, 1986). Group by retention interval interactions, however, can reflect either differential registration or differential forgetting rates and ceiling effects in the performances of normal elderly in the previous studies preclude definitive interpretation. In the present study groups of patients with DAT, depressed, and normal elderly were tested in a Brown-Peterson task with zero and three interpolated distractor items. To tease apart the interpretations of registration and rate of forgetting, groups were equated for immediate recall differences by testing each individual in the Brown-Peterson task with to-be-remembered sequences equal to higher span of immediate memory. Memory spans were found to differ between all three groups (Normal > Depressed > DAT patients) and analysis of the Brown-Peterson task revealed a main effect of group and a group by retention interval interaction. No significant differences were found between groups in immediate recall but DAT patients recalled with lower accuracy than depressed and normal elderly in the delayed recall test. The delayed serial recall performance of depressed elderly was not significantly different from that of normal elderly. The present findings suggest that memories of patients with DAT are subject to a greater rate of loss than those of normal elderly and they are consistent with a model of DAT in which deficits occur at multiple loci in the memory system. The superior delayed recall performance of depressed elderly relative to patients with DAT suggests the diagnostic potential of the Brown-Peterson task in discriminating between these groups.     

Performance of alcoholic and brain-damaged subjects on the Luria memory words test

Verbal memory was evaluated in groups of 36 community controls, 50 pseudoneurological controls, 50 alcoholics, and 50 brain-damaged patients. All participants were men between the ages of 22-61. Groups did not differ in age or educational levels (F < 1). Groups were compared on their performance on the Luria Memory Words Test. Dependent variables included the number of correct words over learning trials, the trial of best performance, and the number of words recalled at three delayed trials (2, 8, and 30 min after learning). Brain-damaged subjects were inferior to community controls on all measures. Pseudoneurological controls were inferior to community controls on delayed recall, but were equivalent on measures of learning. Alcoholics were inferior to controls on measures of learning but did not differ on measures of recall. Implications regarding the underlying deficit in alcoholics' verbal memory, the use and interpretation of the Luria Memory Words test, and the use of pseudoneurological patients as controls are discussed.     

Dissociations in hippocampal and frontal contributions to episodic memory performance

The hippocampus and frontal lobes both contribute to episodic memory performance. In the present study, the authors evaluated the relative contributions of hippocampus, frontal lobes, anterior temporal cortex, and posterior cortex to memory performance in neurodegenerative patients and normal older controls. Subjects (n=42) were studied with structural MRI and a memory paradigm that measured delayed recall, semantic clustering during recall, recognition discriminability, and recognition response bias. Data were analyzed with multiple regression. Consistent with the authors' hypotheses, hippocampal volumes were the best predictor of delayed recall and recognition discriminability, whereas frontal volumes were the best predictor of semantic clustering and response bias. Smaller frontal volumes were associated with less semantic clustering during recall and a more liberal response bias. Results indicate that hippocampal and frontal contributions to episodic memory can be dissociated, with the hippocampus more important for memory accuracy, and frontal structures more important for strategic processing and decision making.     

The relationship between theta-gamma coupling and spatial memory ability in older adults

Although theta-gamma coupling is known to reflect memory-related processes, it is unclear whether it has a relationship with memory ability. Here, we investigated the relationship between theta phase and gamma power coupling (TGC) and scores obtained regarding memory tasks. Thirty-one older subjects performed a spatial delayed match-to-sample task (SDMST) during EEG recording. We also evaluated performance on the delayed figure recall (DFR) and delayed verbal recall (DVR) tasks regarding memory ability. Partial correlation analysis (controlled for age) demonstrated that increases in TGC in the parietal area were significantly correlated with increases in the DFR scores obtained. In addition, TGC was significantly correlated with the accuracy rate of the SDMST. Our results indicate that TGC could be a useful biophysiological marker of memory ability.     

Childhood head injury and metacognitive processes in language and memory

We studied the metacognitive functioning of children with severe and mild traumatic brain injury (TBI) and typically developing children. To test metacognition for memory, children were tested on a modified Judgment of Learning task. We found that children with severe TBI were impaired in their ability to predict recall of specific items prior to study-recall trials, but were unimpaired in predicting recall on a delayed test when the judgment was made after study-recall trials. Metacognitive knowledge impairment for memorial abilities was also demonstrated in children with severe TBI by poor estimation of memory span and exaggerated overconfidence in performance. To test metacognition within the language domain, we gave children a sentence anomaly detection and repair task in which spoken sentences were monitored for semantic anomalies. Children with severe TBI were impaired on the detection of semantic anomalies, especially under conditions of high memory load. However, metalinguistic knowledge in the form of adequate repairs of anomalous sentences, was preserved. Results are discussed in terms of effects of age at test and injury severity.     

Childhood Head Injury and Metacognitive Processes in Language and Memory

We studied the metacognitive functioning of children with severe and mild traumatic brain injury (TBI) and typically developing children. To test metacognition for memory, children were tested on a modified Judgment of Learning task. We found that children with severe TBI were impaired in their ability to predict recall of specific items prior to study-recall trials, but were unimpaired in predicting recall on a delayed test when the judgment was made after study-recall trials. Metacognitive knowledge impairment for memorial abilities was also demonstrated in children with severe TBI by poor estimation of memory span and exaggerated overconfidence in performance. To test metacognition within the language domain, we gave children a sentence anomaly detection and repair task in which spoken sentences were monitored for semantic anomalies. Children with severe TBI were impaired on the detection of semantic anomalies, especially under conditions of high memory load. However, metalinguistic knowledge in the form of adequate repairs of anomalous sentences, was preserved. Results are discussed in terms of effects of age at test and injury severity.     

Incidental recall on WAIS-R digit symbol discriminates Alzheimer's and Parkinson's diseases

The purpose of this study was to examine how Alzheimer's (n = 37) and Parkinson's (n = 21) patients perform on the incidental recall adaptation to the Digit Symbol of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and how such performance is related to established cognitive efficiency and memory measures. This adaptation requires the examinee to complete the entire subtest and then, without warning, to immediately recall the symbols associated with each number. Groups did not differ significantly on standard Digit Symbol administration (90 seconds), but on recall Parkinson's patients recalled significantly more symbols and symbol-number pairs than Alzheimer's patients. Using only the number of symbols recalled, discriminate function analysis correctly classified 76% of these patients. Correlations between age-corrected scaled score, symbols incidentally recalled, and established measures of cognitive efficiency and memory provided evidence of convergent and divergent validity. Age-corrected scaled scores were more consistently and strongly related to cognitive efficiency, whereas symbols recalled were more consistently and strongly related to memory measures. These findings suggest that the Digit Symbol recall adaptation is actually assessing memory and that it can be another useful way to detect memory impairment.     

Effects of distraction and stress on delayed matching-to-place performance in aged rats

The performance of male Long-Evans rats on the delayed match-to-place (DMP) version of the Morris water maze was assessed in two separate experiments; the first compared young (4 months) with middle-aged (16 months) rats, whereas the second compared middle-aged (14 months) with old (26 months) rats. Old rats continued to use a short-term memory strategy on the DMP task, but their performance on both search and recall trials was impaired relative to that of middle-aged animals. Rats of all ages habituated rapidly to visual distraction and the performance of old rats was not affected by exposure to a mild predator stress in the form of cat urine. The performance of the middle-aged rats did not differ significantly from that of young rats, even when they were challenged on recall trials by visual distraction or by exposure to predator odour. These results do not provide strong support for the prediction that visual distraction and psychological stress would interact with age in affecting spatial short-term memory in Long-Evans rats.     

Verbal memory tests in the differential diagnosis of depression and dementia: discriminative power of seven test variations.

The many tasks for the assessment of verbal memory differ widely in features of presentation and retrieval. In this study, seven common memory tasks (immediate and delayed free recall, randomized presentation, selective reminding, serial recall, recognition after short and long delay) were compared for their discriminative power between depressed, demented, and healthy elderly subjects. Tasks that require little cognitive capacity were hypothesized to be particularly useful to differentiate the patient groups. Demented and depressed patients demonstrated deficits on all tests, the demented being more severe. Only recognition after long and short delay, and delayed recall distinguished demented from depressed patients. Delayed retrieval tasks were more useful to discriminate patient groups than tasks that require little cognitive capacity.     

Recreational use of 3,4-methylenedioxymethamphetamine (MDMA) or 'ecstasy': evidence for cognitive impairment

BACKGROUND: It has recently been shown that 3,4-methylenedioxymethamphetamine (MDMA) or 'ecstasy' causes long-lasting alterations to brain structure and function in animals, and there is mounting evidence that recreational users of the drug show impairments in some aspects of cognitive functioning including memory for verbal information. The present study investigates possible effects on other cognitive functions and explores the temporal course of development and resolution of these impairments by comparing novice, regular and abstaining users with a matched group of non-users. METHODS: Eighty participants categorized as non-users, novice users, regular users or currently abstinent users of MDMA were assessed on tests of verbal IQ, reversed digit span, immediate and delayed recall of a prose passage and of a complex geometric figure and verbal fluency. RESULTS: The four groups were well-matched for verbal IQ and on demographic variables. They differed in frequency of cannabis use over the last month, but this did not correlate with any cognitive test scores. All three groups of MDMA users showed significantly poorer verbal fluency and immediate and delayed prose recall than non-users. Days since last use and total lifetime consumption of MDMA made separate contributions to the variance in recall scores, accounting jointly for almost half of the variance in delayed recall. By contrast, the groups did not differ on either visual recall or reversed digit span. CONCLUSIONS: The observed deficits provide further evidence of impairments of verbal but not visual memory in MDMA users, and indicate that the deficits are not attributable either to differences in general reasoning ability or to impairment of working memory. The data further suggest that the observed impairments may be attributable to a combination of reversible acute effects of MDMA resolving over a period of 2-3 weeks and more long-term changes associated with extent of lifetime consumption.     

Psychometric construction of the Rey-Osterrieth Complex Figure: methodological considerations and interrater reliability.

Formal scoring criteria for the standard 18 elements of the Rey-Osterrieth Complex Figure were developed and applied to reproductions of 87 healthy young adults. In addition, the effects of immediate recall on delayed performance was investigated. Results indicate (a) the formal scoring criteria can be reliably applied by independent raters; (b) 30-minute recall is significantly higher if immediate reproduction is included compared to 30-minute delay performance without immediate recall; (c) significantly fewer qualitative scoring errors are present at the 30-minute delay if immediate memory is previously assessed; and (d) in addition to an absence of decay over a 30-minute delay, performance significantly improves over this interval. These findings underscore the caution that must be exercised when making specific inferences from test scores alone based upon measures that were obtained in a variety of contexts employing unspecified scoring criteria.     

Recall and recognition memory deficits in depression.

The aim of the present study was to establish the nature of memory deficits of depressive subjects in word learning tests. A word learning test consisting of 1, 3 or 5 learning trials was used. We found that patients were characterized by inferior memory recall compared to controls when 5 learning trials were given. Patients performed significantly slower than controls on a recognition test but both patients and controls recognized the same number of words. This suggests that the memory deficits that are present in many depressive subjects may be restricted to impaired active retrieval from memory. A second experiment revealed that recognition memory and delayed recall as well as immediate recall were impaired in depressive patients after 1 learning trial. These short-comings vanished after 3 trials, except for immediate recall. These data suggest that not only retrieval but also encoding of information into memory may be impaired in depression, especially in the beginning of a task when demands on cognitive effort are high. The results are discussed in terms of resource allocation and demands on effort that may change in the course of a task.     

Factor analysis of the Wechsler memory scale: Is the associate learning subtest an unclear measure?

A factor analysis of the Wechsler Memory Scale (WMS) with 30-minute delayed recall scores (percent retained) for the Logical Memory, Visual Reproduction, and Associate Learning subtests indicated that this variant of the WMS taps different types of learning and memory for new material. With regard to the verbal learning/recall subtests, Logical Memory appears to be related to attention/ concentration ability, while Associate Learning is relatively independent. The results also showed that both the easy and hard items from Associate Learning tap the same ability, providing evidence that this subtest is a measure of rote verbal learning. These results support the clinical utility of the WMS with delayed recalls in neuropsychiatric populations.     

What does a patient with semantic dementia remember in verbal short-term memory? Order and sound but not words

In this study, we explored capacities for three different aspects of short-term verbal memory in patients with semantic dementia. As expected, the two patients had poor recall for lexico-semantic item information, as assessed by immediate serial recall of word lists. In contrast, their short-term memory for phonological information was preserved, as evidenced by normal performance for immediate serial recall of nonword lists, with normal or increased nonword phonotactic-frequency effects, and increased sensitivity to phonological lures in a delayed probe recognition task. Furthermore, the patients appeared to have excellent memory for the serial order of the words in a list. These data provide further support for the proposal that language knowledge is a major determining factor of verbal STM capacity, but they also highlight the necessary distinction of processes involved in item and order recall, as proposed by recent models of STM.     

Material-specific memory in traumatic brain injury: differential effects during acquisition, recall, and retention

Material-specific memory refers to the ability to learn and recall new episodic information on the basis of the nature of the stimulus material (e.g., verbal vs. nonverbal-visuospatial). Structural equation modeling was used to analyze data from a sample of patients with traumatic brain injury to compare 3 models of memory functioning: material-specific, material-specific plus general, and general (non-material-specific). The models were examined separately for acquisition, delayed free recall, and retention aspects of memory. Results suggest that, at least in a population with traumatic brain injury, the acquisition of new information takes place in a material-specific memory fashion, delayed free recall involves both material-specific and general (non-material-specific) memory components, but retention relies primarily on general (non-material-specific) memory processes.     

Consolidation of temporal order in episodic memories

Even though it is known that sleep benefits declarative memory consolidation, the role of sleep in the storage of temporal sequences has rarely been examined. Thus we explored the influence of sleep on temporal order in an episodic memory task followed by sleep or sleep deprivation. Thirty-four healthy subjects (17 men) aged between 19 and 28 years participated in the randomized, counterbalanced, between-subject design. Parameters of interests were NREM/REM cycles, spindle activity and spindle-related EEG power spectra. Participants of both groups (sleep group/sleep deprivation group) performed retrieval in the evening, morning and three days after the learning night. Results revealed that performance in temporal order memory significantly deteriorated over three days only in sleep deprived participants. Furthermore our data showed a positive relationship between the ratios of the (i) first NREM/REM cycle with more REM being associated with delayed temporal order recall. Most interestingly, data additionally indicated that (ii) memory enhancers in the sleep group show more fast spindle related alpha power at frontal electrode sites possibly indicating access to a yet to be consolidated memory trace. We suggest that distinct sleep mechanisms subserve different aspects of episodic memory and are jointly involved in sleep-dependent memory consolidation.