Biomedical subjects

P R Meudell

Publications and source records attributed to P R Meudell.

At least 19 recordsLinked to original sources

PubMed2000

New learning and remote memory in the same and different domains of experience: implications for normal memory and amnesia.

This study investigated the correlation between new and remote memory ability in normal young subjects and evaluated whether using tests that tapped different domains of experience had any effect on the relationship between new and remote memory. Remote memory was assessed using a famous face test and new memory was evaluated using both novel faces and words. The main finding was a significant correlation between New and Remote face familiarity scores. A correlation was obtained when both tests tapped the same domain of memory, whereas when tests tapped different domains, there was no Remote-New correlation. Remote-New correlations may only exist between tests tapping the same domain of memory. This has implications for the interpretation of previous amnesic literature and for future investigations.

Adolescent↗

PubMed2000

Mutual inhibition in collaborative recall: evidence for a retrieval-based account.

In Experiment 1 participants gave 3 successive free recalls of items learned either individually or in pairwise collaboration. The first and third recalls were performed individually, the second alone or in collaboration. Collaborative recall led to an inhibitory effect after individual learning but not after collaborative learning, in which partners had similar retrieval strategies. Consistent with a retrieval locus for collaborative inhibition, non-recalled items reappeared in subsequent individual recall. Experiment 2 showed that collaborative inhibition was eliminated when a separate retrieval cue was given for each item. Experiments 2 and 3 also showed that when participants learned items in the same order, their retrieval strategies were more similar and they showed less collaborative inhibition. It is concluded that mutual interference in collaborative recall is due to the mutual disruption of individual retrieval strategies.

Adult↗

PubMed1999

Do novel associative word stem completion and cued recall share the same memory retrieval processes?

The aim of this study was to determine whether word stem completion for novel associations between cue and target words was mediated by automatic unconscious memory processes or effortful memory processes under conscious control. This was done by applying full and divided attention conditions at test to stem completion, cued recall, and recognition, and by administering a questionnaire that probed the memory strategies used by subjects during the completion test. Divided attention had no effect on stem completion performance, but did reduce associative cued recall. Recognition performance was weakened overall by divided attention, but the associative effect was similar under both attention conditions. This suggested that novel associative word stem completion was mediated by automatic retrieval processes. However, the results of the questionnaire indicated that only subjects who attempted to remember the words from the study phase during the completion task showed any novel associative effect. It is concluded that novel association word stem completion and cued recall share automatic retrieval processes, which nevertheless give rise to the experience of remembering.

Adult↗

PubMed1999

Shattered illusions: the effect of explicit memory mediation on an indirect memory test.

Four experiments were conducted to explore the possible involvement of explicit memory in an indirect memory test in which white noise accompanying old sentences was judged to be quieter than white noise accompanying new sentences (Jacoby, Allan, Collins & Larwill, 1988). Experiment 1 established that this effect lasted up to 1 week. Experiment 2 found that a group of amnesic patients showed a noise effect that was marginally above chance and not significantly less that that of their matched controls after a delay of one day. Effect of time pressure at test (Experiment 3) and divided attention at study (Experiment 4) suggested that the memory processes mediating the noise effect were not automatic, although the possibility that the processes involve enhanced fluency is also discussed.

Adult↗

PubMed1998

Simulating a memory impairment: can amnesics implicitly outperform simulators?

OBJECTIVES: The purpose of this study was to examine the effectiveness of a variety of tests in differentiating simulating test performances from genuine memory-impaired and normal (control) test performances. DESIGN: A simulation design was implemented, based on an analogue design in which normal participants were given experimental instructions to feign a mental impairment and are compared to (a) other normal participants with instructions to perform honestly, and (b) a comparison group, for example, acquired brain-injured persons, with similar instructions. METHOD: Forty individuals comprised the simulating and control group and all participants were randomly assigned to the simulating and control groups. Twenty memory-impaired patients, all of whom had been diagnosed as suffering from a memory impairment following acquired brain damage, participated as the memory-impaired control group. The simulation group was directed to imitate a person with a memory impairment. The primary outcome measure involved identifying those tests, if any, where simulators were significantly different from normal and memory-impaired participants. RESULTS: On 5 of the 15 tasks administered, simulators performed significantly differently from normal and memory-impaired participants. Of these 5 tasks, the coin-in-the-hand, when administered in conjunction with the autobiographical interview, identified 95 per cent of the simulators without misclassifying any of the memory-impaired or normal participants. CONCLUSION: It is suggested that these two tests, when administered jointly, might be of use in clinical settings to assist in the detection of malingerers.

Adult↗

PubMed1996

Autonomic and recognition indices of memory in amnesic and healthy control subjects.

Autonomic and recognition indices were examined in six amnesic subjects of mixed aetiology and six control subjects matched with respect to age, education and intelligence. The key objectives of this study were: (a) assess amnesics level of recognition and autonomic discrimination for recently shown words compared with controls; (b) determine if amnesics' level of autonomic discrimination was preserved when compared with the control subjects, level of recognition; and (c) assess confidence in hits and false alarms. The results showed that: (1) despite showing impaired recognition, amnesics displayed significantly better autonomic discrimination; (2) the level of autonomic discrimination displayed by amnesics did not significantly differ from the control subjects' level of recognition; (3) the level of confidence expressed in false alarms and hits did not significantly differ between amnesics and controls, which is in sharp contrast to the significantly greater levels of confidence expressed by healthy subjects in hits versus false alarms. If future work shows that amnesics display preserved autonomic discrimination for novel information, then it may suggest that, at least, some amnesics can store information to an extent that is comparable to that of healthy controls.

Adult↗

PubMed1995

Collaboration in recall: do pairs of people cross-cue each other to produce new memories?

When people collaborate over their recall of a shared experience, it might be expected that they could "cross-cue" each other so as to produce new memories not available to either member of the pair on their own. In a previous series of experiments (Meudell et al., 1992), we found that pairs of people always recalled more than one person, but we failed to show that social interaction facilitated performance so as to produce such "emergent" new memories. However, a phenomenon akin to cross-cuing was employed by Tulving and Pearlstone (1966) in their classic study of the availability and accessibility of memories; accordingly, in this study, we repeated Tulving and Pearlstone's work directly in a social context. So as to assess whether new memories emerged in collaborating pairs, a sequential design was employed. People learned categorized lists of words, and then all the subjects recalled the items strictly on their own. Subjects then recalled again in pairs (collaboratively) or once more on their own. The results showed that even when the opportunity for cross-cuing was directly manipulated through the provision of categorized lists, no additional new memories emerged in the collaborating groups. Possible mechanisms for the results are considered.

Adolescent↗

PubMed1994

Dual task performance in amnesic and normal people: does resource depletion cause amnesia?

Normal peoples' memory can be seriously disrupted if their cognitive resources are depleted by means of an experimental manipulation (such as distraction at encoding or at retrieval). By analogy, it has also been suggested that amnesia might result directly from pathological loss of cognitive capacity. This hypothesis was examined in 12 mixed amnesics and 12 normal people by means of a 'dual task' study. It was argued that if amnesics have reduced cognitive resources they should be disproportionately impaired in dual task performance relative to single task performance and in comparison to controls. This result was unambiguously demonstrated using a visual (letter detection) task combined with an auditory (semantic decision) task. However, correlations with measures of frontal function and with indicants of severity of amnesia proved insignificant and so the role of resource depletion in amnesia remains, as yet, unproven.

Adult↗

PubMed1994

Two tests for assessing remote public knowledge: a tool for assessing retrograde amnesia.

Guidelines for the construction and development of tests of remote memory are provided. These guidelines follow from methodological considerations and from certain theoretical issues we believe that remote memory tests should address if they are to further our understanding of amnesia. These include: the pattern of temporal gradient; memory for different broad classes of information such as famous names and famous events; and recall and recognition of different types of detail such as contextual and non-contextual information associated with remote memory. With respect to the first of these, we argue that it is impossible to fully evaluate competing hypotheses about temporally graded retrograde amnesia unless items are selected from at least two difficulty levels, and from at least two time periods. The construction of two equivalent tests of remote memory, one for famous people, the other for famous events, is described, and the theoretical issues listed earlier were addressed using these tests in a study comparing the remote memory of 13 organic amnesics and 13 age- and IQ-matched controls. The principal findings were as follows. There was only weak evidence that amnesics' remote memory for famous people and events was temporally graded over a 20 year period, and recognition memory and memory for non-contextual detail were equally impaired. Mayes, Meudell, and Pickering's (1985) context memory deficit hypothesis was supported, however, because amnesics were more impaired in their ability to date recognised items. In addition, although there was little support for a temporally graded retrograde impairment on the recognition question, there was much clearer evidence for the temporal dating question. Also, one patient, SR, showed a selective deficit in dating recognised names and events from the 1980s. Finally, the correlations between measures of anterograde and retrograde amnesia were all non-significant. Suitable items for the construction of remote memory tests probing the four decades 1950s to 1980s are presented. A subset of these, from the 1970s and 1980s, were shown to have satisfactory psychometric qualities, and can therefore be recommended for more widespread clinical use, although more extensive normative data than that provided here will be necessary.

Adult↗

PubMed1992

Priming of face matching in amnesia.

Priming was studied in a task that required a speeded response to photographs of faces. On each trial, subjects viewed two faces and decided if the same person was shown twice or if two different people were shown. Both familiar and unfamiliar (i.e., well-known and unknown) faces were used, and some face pairs were repeated with a mean delay of about 10 min. Repetition was associated with faster reaction times in young subjects (Experiment 1) as well as in amnesic patients and age-matched control subjects (Experiment 2). The patients' reaction times were slower overall, although the magnitude of the priming effect did not differ from that in the control subjects. This preservation of a normal reaction-time facilitation in subjects with impaired recognition memory for faces occurred for both familiar and unfamiliar faces, suggesting that amnesia does not necessarily interfere with the acquisition of new information as indexed by this priming effect.

Adult↗

PubMed1992

Amnesics have a disproportionately severe memory deficit for interactive context.

Two experiments were used to compare the recognition memory of amnesic and normal subjects for intentionally encoded words (targets) and for incidentally encoded words that were meaningfully related to the targets and presented at the same time (interactive context). In both experiments the target recognition of the two groups was matched at a high level by presenting the amnesics with much shorter lists of words to remember. Experiment 1 compared 20 amnesics and their matched controls and showed that whereas the amnesics' recognition of the target words did not benefit significantly when they were presented together with their interactive context words (relative to their recognition when the target words were presented alone), that of the controls did. Experiment 2 compared 14 amnesics and their matched controls and showed that when patients and their controls were matched on their target word recognition in isolation, then the patients still showed worse recognition for the interactive context words. These effects were not found only in Korsakoff patients, and their size did not correlate with behavioural measures of frontal-lobe damage. It is concluded that amnesics may be more impaired at recognizing incidentally encoded interactive context than they are at recognizing target material, and this deficit may be an essential feature of the syndrome.

Adult↗

PubMed1991

Indirect measures of memory in a duration-judgement task are normal in amnesic patients.

Nine amnesic patients of mixed aetiology were studied in a duration-judgement task that allowed three measures of memory to be obtained. On each trial of the task, subjects attempted to read a briefly flashed word and to estimate the duration of the flash. Both word identification and duration estimation differed as a function of prior study. Words that were previously studied were identified more often and were estimated to have been flashed for a longer duration than were words not previously studied. These priming effects were found in young subjects in Experiment 1 and in amnesic patients and age-matched control subjects in Experiment 2. Priming effects were normal in the amnesic patients, whereas these patients were severely impaired at recognizing the same words. Previous results have also shown that amnesic patients can perform normally on certain memory tests, including priming of word identification. These results show that priming of duration judgements can also be included in the category of indirect measures of memory that are spared in amnesia.

Adult↗

PubMed1991

Disproportionate intentional spatial-memory impairments in amnesia.

Twenty-four amnesics, including patients with Korsakoff's disease, post-encephalitic amnesia and amnesia caused by rupture of an anterior communicating artery aneurysm (ACoAA), were compared with 24 matched control subjects on a task in which words were presented in any one of four positions on a computer screen and subjects were instructed to remember both the words and their locations. The patients were tested after more learning opportunity, exposure to shorter lists, and after shorter delays than were their controls in order to match the word recognition performance of the two groups. Under these conditions, the amnesics' ability to locate recognized words was significantly worse than that of their controls. Although there was a tendency for the ACoAA patients to show more severe spatial memory deficits than Korsakoff patients, there was no clear evidence that aetiology of amnesia was a critical determinant of whether spatial memory was more impaired than word recognition. It was concluded that amnesics show a disproportionately severe memory deficit for spatial information that is intentionally encoded as well as for that which is incidentally encoded.

Adolescent↗

PubMed1991

Korsakoff amnesics are poor at judging the sequence of two tones.

Alcoholic amnesics were given a test of temporal sequencing ability devised by Efron which has practically no memory component. These amnesics were very impaired on the task. However, the extent of this impairment did not relate to the magnitude of their "target memory" deficit nor did it relate to the ability to make temporal judgements from memory. Two other groups of amnesics (3 post-encephalitis and 4 with ruptured aneurysms of the anterior communicating artery) did not show impairments on the sequencing task. Data from the amnesic patient N.A. (who was unimpaired on the task), three other amnesics (who showed a tendency to be poor at the task) and two frontally damaged patients (one of whom performed especially badly on the sequencing task but had no obvious memory difficulties) were also presented. It is argued that deficits in temporal discrimination may not be found in all amnesics but, when they are observed, are an incidental feature related to additional (possibly cortical damage. Implications of the results for the view that amnesia results from a deficit in the use of contextual information (including temporal information) are considered.

Adult↗

PubMed1989

Why are amnesic judgements of recency and frequency made in a qualitatively different way from those of normal people?

The Huppert and Piercy (1978) test of recency and frequency judgements was given to a group of 12 non-Korsakoff amnesics of mixed aetiology and to four non-amnesic patients with selective frontal lobe lesions. The results confirmed that non-Korsakoff amnesics show a significant tendency to base their recency and frequency judgements on memory strength and that amnesics with medial temporal lobe damage show this tendency at least with recency judgements. The patients with frontal lobe lesions performed like normal subjects. Patients who were dysexecutive or impaired in cognitive resources were less likely to base recency judgements on trace strength. Such a recency bias was not however, correlated with measures of amnesic severity. The tendency to base frequency judgements on memory strength was not related to either degree of amnesia or reduction of cognitive resources.

Adult↗

PubMed1988

Location of lesions in Korsakoff's syndrome: neuropsychological and neuropathological data on two patients.

Psychometric and neuropathological findings on two Korsakoff amnesics are described. Both patients showed anterograde and retrograde amnesia, poor performance on the Peterson short-term memory task, on the Wisconsin card sort test and on certain visuo-spatial tasks. Patient J.W. performed consistently worse on tests of anterograde, but not retrograde amnesia, whereas patient B.C. showed more perseverative difficulties and, unlike J.W., his measured intelligence seemed to have declined from its premorbid level. Both patients showed marked neuronal loss from the medial mammillary bodies and a narrow band of gliosis in the medial thalamus, adjacent to the wall of the third ventricle, a region known as the paratenial nucleus. Only B.C. showed visible signs of cortical atrophy. Morphometric measures did, however, reveal reduced nucleolar volumes in layers III and V of the frontal cortex, with B.C. also showing more marked neuronal loss from these layers. B.C. also showed neuronal loss from the CA1 region of the hippocampus and reduced nucleolar volumes in the septum. Significantly, both patients had normal neuronal numbers and nucleolar volumes in the nucleus basalis of Meynert. J.W. only showed greater dysfunction than B.C. in one region: the locus caeruleus. This finding was related to his more severe amnesia.

Aged↗

PubMed1987

Age related differences in left and right hand skill and in visuo-spatial performance: their possible relationships to the hypothesis that the right hemisphere ages more rapidly than the left.

Young and old right handed people were disproportionately worse with their left hand when speed was stressed but showed no especial difficulty when accuracy of performance was emphasised. Both groups of people were also tested on the AH4 test of cognitive abilities. As frequently reported by Rabbitt, the old were disproportionately worse on the visuo-spatial part than on the verbal part compared with the young, even though both parts required "fluid" abilities and even though both were given under time constraints. There was no correlation amongst the elderly people between speed stressed deficits in their left hand performance and their deficits on the visuo-spatial part of the AH4. Both fine control of the left hand and fingers and visuo-spatial performance are likely to be mediated by the right cerebral hemisphere and the implications of these results for a variety of possible views about selective aging of the right hemisphere are discussed.

Adolescent↗

PubMed1985

Recency and frequency judgements in alcoholic amnesics and normal people with poor memory.

Alcoholic amnesics have been reported to confuse when an event occurred with how frequently it occurred and conversely, how frequently something took place with when it happened. This lack of independence of recency and frequency judgements, shown by these amnesics (but not shown by normal people) has been interpreted as reflecting a selective amnesic failure in memory for contextual information; this failure, in turn, leading to poor recall and recognition memory. The effect is replicated on another group of Korsakoff patients and, by manipulations of retention intervals and of learning opportunity, it is also shown that normal people with memory that is as poor overall as that of amnesics still have specific contextual memory with which to make temporal judgements independently of frequency of presentation and (somewhat less obviously) frequency judgements independently of recency of presentation. The qualitative differences between amnesic and normal people cannot therefore be an artefact of testing generally poor memory in amnesics. While it is possible that the unavailability or inaccessibility of contextual information may cause amnesia, an alternative hypothesis, that poor contextual knowledge is an incidental feature in alcoholic amnesia (related to frontal lobe dysfunction), is also considered.

Alcohol Amnestic Disorder↗