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Biomedical subjects

A D Baddeley

Publications and source records attributed to A D Baddeley.

At least 37 records · Page 2Linked to original sources
PubMed1996

Analysis of the episodic memory deficit in early Alzheimer's disease: evidence from the doors and people test.

Anterograde episodic memory was assessed in a cohort of 33 patients with early dementia of Alzheimer type (DAT) and 30 matched controls using immediate and delayed prose recall, the CERAD word learning test and the recently developed doors and people test of visual and verbal recall and recognition. DAT patients showed markedly impaired learning on all three measures, with little evidence of cumulation of information across trials. Patients showed more forgetting than controls on prose recall and the CERAD word list, but more detailed analysis suggested that this differential loss was attributable to the contribution of primary memory to immediate but not delayed recall. No differences in forgetting rate were observed on the doors and people test. Scaled scores were used to derive a recall-recognition index, together with a measure of material-specific memory based on the ratio of verbal to visual memory deficits. There was no evidence for differential sensitivity of recall over recognition, implying that the episodic memory deficit is one of learning, rather than of the retrieval of learned material. Although individuals varied in the relative degree of impairment of verbal and visual memory, there was no general tendency for material-specificity. It was concluded that the episodic memory deficit in DAT is general in nature and primarily reflects impaired learning rather than accelerated forgetting or disrupted retrieval.

Aged↗
PubMed1995

Autobiographical memory and executive function in early dementia of Alzheimer type.

We studied executive function and autobiographical memory in a cohort of 33 DAT patients [divided into minimal (MMSE 24-30) and mild (MMSE 17-23) groups] and in 30 normal controls. Autobiographical memory, as assessed by autobiographical fluency and the Autobiographical Memory Interview (AMI), was impaired in DAT patients, even those with minimal disease. There was evidence of a gentle temporal gradient on the incident but not the personal semantic component of the AMI, suggesting that the two components are dissociable. Executive function was assessed by two separate dual performance tasks and letter fluency. Although there was a trend for minimal DAT patients to be impaired on executive tasks, this only reached significance for the mild group. Regression analysis suggested that the divided attention component of working memory was involved in the retrieval of personal semantic autobiographical memory, but verbal fluency was more important in the retrieval of autobiographical incidents. There was thus a dissociation in the type of executive function implicated in different subcomponents of autobiographical memory, arguing for subcomponents within executive function and autobiographical memory. The autobiographical memory deficit in DAT reflects, we argue, both impairment in retrieval processes, linked to executive function, and a loss of memory stores.

Age of Onset↗
PubMed1995

Methodological considerations in estimating speed of cognitive operations.

Individuals infected with Human Immunodeficiency Virus (HIV) and having cognitive impairment have been described as having slow mentation. Data supporting this proposition come from a variety of sources, including Sternberg's (1966) item recognition memory task. The procedure nominally provides an index of speed of mental operations, independent from input/output demands. However, since the original use of this procedure in the 1960s, advances in cognitive psychology have revealed many of its limitations. The purpose of the present study was to examine the psychometric characteristics of this task. Each participant performed the Sternberg item recognition task twice, 6 mo apart. The stability of the estimate of the slope of regression equations and for zero intercept ranged from excellent (r = .87) to poor (r = .30), and the data from many individual subjects could not be reliably modelled using multiple linear regression techniques. These data, as well as those from previous research, demonstrate the limited practical use of this task in clinical samples. Furthermore, as cognitive psychological theory has advanced in the past 30 yr, the conceptual underpinnings of the procedure have essentially evaporated.

AIDS Dementia Complex↗
PubMed1995

Dense amnesia in a professional musician following herpes simplex virus encephalitis.

We describe the memory functioning of C, a professional musician who became amnesic following herpes simplex encephalitis in 1985. Although transient amnesia in a professional musician has previously been described, this is the first reported case of chronic amnesia in a highly talented professional musician. C is unusual in three respects. First, his amnesia is particularly severe. Second, his amnesia includes semantic as well as episodic memory deficits. Third, he believes he has just woken up and his preoccupation with this state of 'just wakening' has persisted for over 9 years. This appears to be the result of a delusion rather than the consequence of his amnesia.

Amnesia↗
PubMed1995

Stimulus-independent thought depends on central executive resources.

Stimulus-independent thoughts (SITs) are streams of thoughts and images unrelated to immediate sensory input. Four experiments examined the contribution of aspects of working memory to production of SITs. In Experiments 1 and 2, interventions that were targeted on, respectively, phonological and visuospatial components of working memory both interfered with production of SITs, but there was evidence that these tasks also made demands on central executive resources. Experiments 3 and 4 specifically examined the hypothesis that production of SITs and control of nonproceduralized tasks both depend on central executive resources, and so should show mutual interference. In Experiment 3, prior practice on pursuit rotor and memory tasks reduced the interference with SITs from concurrent task performance. In Experiment 4, randomness within a task involving random-number generation was less when SITs were being produced concurrently than it was when they were not. The results suggest that production of SITs depends on central executive resources.

Adult↗
PubMed1994

The Children's Test of Nonword Repetition: a test of phonological working memory.

This article presents findings from the Children's Test of Nonword Repetition (CNRep). Normative data based on its administration to over 600 children aged between four and nine years are reported. Close developmental links are established between CNRep scores and vocabulary, reading, and comprehensive skills in children during the early school years. The links between nonword repetition and language skills are shown to be consistently higher and more specific than those obtained between language skills and another simple verbal task with a significant phonological memory component, auditory digit span. The psychological mechanisms underpinning these distinctive developmental relationships between nonword repetition and language development are considered.

Case-Control Studies↗
PubMed1994

The Extended Rivermead Behavioural Memory Test: a measure of everyday memory performance in normal adults.

The Rivermead Behavioural Memory Test provides a well-validated instrument for detecting everyday memory problems in patient groups. It was however designed as a screening test, and thus is insufficiently sensitive to detect mild deficits, whether due to brain damage or to the introduction of a drug or stressor. The Extended Rivermead Behavioural Memory Test (ERBMT) increases the level of difficulty by doubling the amount of material to be remembered, by combining material from Forms A and B, and Forms C and D of the original test to produce two parallel versions of the new extended test. The sensitivity of the ERBMT was assessed by comparing the performance of a middle-aged and an elderly group of normal subjects, who would be expected to show modest differences in memory performance. The subtests varied in their sensitivity to this small age difference, but when performance was assessed in terms of scaled scores that allow an overall combined measure of memory performance to be calculated, the test proved sensitive (t = 4.87, P < 0.0001), and free of ceiling and floor effects. We suggest that the ERBMT provides a promising measure of everyday memory in normal adults.

Adult↗
PubMed1993

Memory in schizophrenia: what is impaired and what is preserved?

This study assesses the pattern of long-term memory performance in a sample of 12 schizophrenic patients who were selected on the basis of showing a memory deficit in the absence of gross overall intellectual impairment. When compared with 12 control subjects matched for age, sex and estimated premorbid IQ, presence of an episodic memory deficit was confirmed for both prose recall and forced-choice word and face recognition. Semantic memory was assessed using the sentence verification task developed by Collins and Quillian, an unpaced category judgement task, and the Mill Hill Vocabulary Scale. The schizophrenic patients were slower on sentence verification and they made significantly more errors in all three tasks. Procedural tasks included pursuit rotor performance, speed of repeatedly assembling a jigsaw puzzle and rate of improvement in reading transformed script. Here, while the schizophrenic patients showed poor overall performance on the pursuit rotor and jigsaw learning, their rate of learning on all three procedural tasks was comparable with that of the controls. When examined on two implicit memory tasks involving biasing of spelling of homophones and word stem completion, the patients showed a normal degree of priming in both. Implications for the nature of the memory deficit in schizophrenia are discussed.

Adolescent↗
PubMed1993

The recency effect: implicit learning with explicit retrieval?

The recency effect in free recall features prominently in 1960s' theorizing about short-term memory, but has since been largely ignored. We argue that this stems from a preoccupation with the role of recency in the concept of primary memory and the neglect of its role in a broader working-memory framework. It is suggested that the recency effect reflects the application of an explicit retrieval strategy to the residue of implicit learning within a range of cognitive systems. When retrieved implicitly, the same residue is assumed to form the basis of priming effects. The various criteria for implicit learning described by Tulving and Schacter (1990) are successfully applied to the recency effect, and a retrieval process is outlined that can account for both long- and short-term recency effects. It is suggested that a framework combining recency, priming, and implicit learning provides a basis for understanding one of the most important features of cognition and memory, namely, that of maintaining orientation in time and place.

Attention↗
PubMed1992

Memory impairment in schizophrenia: its extent, affiliations and neuropsychological character.

In a sample of 60 schizophrenic patients encompassing all grades of severity and chronicity memory impairment was found to be prevalent, often substantial, and disproportionate to the overall level of intellectual impairment. The deficits were not easily attributable to poor cooperation, attention or motivation; nor were they related to neuroleptic or anticholinergic medication. Memory impairment was significantly associated with severity and chronicity of illness and also with negative symptoms and formal thought disorder. There was evidence from the sample as a whole, and from a more detailed examination of five patients with relatively isolated deficits, that schizophrenic memory impairment conformed to the pattern seen in the classical amnesic syndrome. Additionally, there was preliminary evidence for a marked deficit in semantic memory.

Adult↗
PubMed1992

Autobiographical fluency: a method for the study of personal memory.

Fifty-five subjects recalled autobiographical episodes or personal facts such as names of friends and teachers, from different lifetime periods. In each case, subjects were given 90 sec in which to retrieve as many items as possible. Also tested was subjects' fluency in generating items from semantic categories (animals, vegetables, British prime ministers, and U.S. presidents). Results of cluster analysis on the fluency tasks showed a dissociation between subjects' ability to retrieve personal episodes, personal semantic information, and nonpersonal semantic information. The dissociations observed in the fluency tasks are interpreted in terms of the different retrieval strategies required for the different types of information sought.

Adult↗
PubMed1991

Long-term recency effects and phonological short-term memory. A neuropsychological case study.

Long-term recency effects were investigated in a left brain-damaged patient, PV, who had a pathologically low auditory-verbal span and a lack of the normal recency effects in immediate free recall of auditorily presented lists of words, attributed to the abnormally reduced capacity of the phonological short-term store component of memory (Vallar and Papagno, 1986). In a task requiring the delayed free recall of a list of anagram solutions the patient showed both a recall performance level and a long-term recency effect comparable to the control group. These findings dissociate long and short-term recency phenomena, which would reflect the operation of different memory components. A collateral finding was PV's difficulty in anagram solving, which may be traced back to the defective function of her phonological short-term store.

Adult↗
PubMed1991

The decline of working memory in Alzheimer's disease. A longitudinal study.

A previous study (Baddeley et al., 1986) explored the hypothesis that patients suffering from dementia of the Alzheimer type (AD) are particularly impaired in the functioning of the central executive component of working memory. It showed that, when patients are required to perform 2 concurrent tasks simultaneously, the AD patients are particularly impaired, even when level of performance on the individual tasks is equated with that of age-matched controls. Although the results were clear, interpretation was still complicated by 2 issues: first, the question of comparability of performance on the separate tests between AD and control patients; secondly, the question of whether our results could be interpreted simply in terms of a limited general processing capacity being more taxed by more difficult dual tasks than by the individual tasks performed alone. The present study followed up the AD and control patients after 6 and 12 mths. We were able to allow for the problem of comparability of performance by using patients as their own control. Under these conditions, there is a very clear tendency for dual task performance to deteriorate while single task performance is maintained. A second experiment varied difficulty within a single task in which patients and controls were required to categorize words as belonging to 1, 2 or 4 semantic categories. There was a clear effect of number of categories on performance and a systematic decline in performance over time. There was, however, no interaction between task difficulty as measured by number of alternatives and rate of deterioration, suggesting that the progressive deterioration in performance shown by AD patients is a function of whether single or dual task performance is required, and is not dependent on simple level of task difficulty. Implications for the analysis of the central executive component of working memory are discussed.

Aged↗
PubMed1990

Interference with visual short-term memory.

Working memory (Baddeley and Hitch 1974) incorporates the notion of a visuo-spatial sketch pad; a mechanism thought to be specialized for short-term storage of visuo-spatial material. However, the nature and characteristics of this hypothesized mechanism are as yet unclear. Two experiments are reported which examined selective interference in short-term visual memory. Experiment 1 contrasted recognition memory span for visual matrix patterns with that for visually presented letter sequences. These two span tasks were combined with concurrent arithmetic or a concurrent task which involved manipulation of visuo-spatial material. Results suggested that although there was a small, significant disruption by concurrent arithmetic of span for the matrix patterns, there was a substantially larger disruption of the letter span task. The converse was true for the secondary visuo-spatial task. Experiment 2 combined the span tasks with two established tasks developed by Brooks (1967). Span for matrix patterns was disrupted by a visuo-spatial task but not by a secondary verbal task. The converse was true for letter span. These results suggest that the impairment in short-term visual memory resulting from secondary arithmetic reflects a small general processing load, but that the selective interference due to mode of processing is by far the stronger effect. Results are interpreted as being entirely consistent with the notion of a specialized visuo-spatial mechanism in working memory.

Adult↗
PubMed1990

Emotional factors in forgetting.

Levinger & Clarke (1961) found that subjects tended to forget more word associations to emotional rather than neutral words. Kline (1981) regarded this study as providing 'irrefutable evidence for the Freudian concept of repression'. On the other hand, results from Kleinsmith & Kaplan (1964) suggested that this effect may reverse after a delay. The present study attempted to replicate Levinger & Clark's result using stimulus words balanced for concreteness and frequency. In addition, recall was tested immediately and after a delay. Associations to emotional material were more poorly recalled immediately than associations to material which was low in emotional valence, but tended to be better recalled a month later. There were no differences in recall of pleasant versus unpleasant material. Results do not support the repression hypothesis, in that emotional material becomes more memorable over time. Moreover, repression should differentially apply to unpleasant rather than pleasant material but no such differences were found.

Attention↗
PubMed1990

Amnesic syndrome in schizophrenia.

Memory impairment is not usually considered to form part of the clinical picture of schizophrenia, except perhaps in severely deteriorated patients. In a survey of 60 patients encompassing all grades of severity and chronicity poor memory performance was found to be common, sometimes substantial, and disproportionately pronounced compared to the degree of general intellectual impairment. Although associated with severity and chronicity of illness, impaired memory was by no means confined to old, institutionalized, or markedly deteriorated patients. The pattern of deficit appeared to resemble that of the classic amnesic syndrome rather than that seen in Alzheimer-type dementia.

Adolescent↗