Biomedical subjects

A R Mayes

Publications and source records attributed to A R Mayes.

At least 55 records · Page 3Linked to original sources

PubMed1995

Cognitive outcome after aneurysm rupture: relationship to aneurysm site and perioperative complications.

We evaluated cognitive outcome in a group of 37 patients who had undergone surgery for rupture and repair of a single intracranial aneurysm at least 6 months previously. We compared outcome--assessed by tests of intelligence, attention, executive functions sensitive to frontal lobe lesions, memory, neglect, and mood, as well as by a specially devised questionnaire--between a group of 20 patients who had aneurysms of the anterior communicating artery and 17 patients who had aneurysms located on other branches of the internal carotid artery. There were no differences in cognitive outcome between patients with anterior communicating artery aneurysms and those with aneurysms on other branches of the internal carotid artery. The patient group as a whole, however, showed impairment in executive functions and some aspects of memory in comparison with normative data. Overall, 65% of the patients were impaired in at least one cognitive domain, with 19% showing executive impairments alone, 14% showing memory impairments alone, and 32% showing deficits in both domains. Cognitive outcome was most strongly predicted by postoperative neurologic events, although clipping of an anterior cerebral artery was associated with a higher impairment rating on a symptom profile completed by patients' relatives, and although preoperative rebleeding of aneurysms predicted impairment of executive function.

Adult↗

PubMed1994

Long lasting indirect memory performance for abstract shapes in amnesics and matched controls.

The speed with which subjects copied complex geometrical shapes was used as an indirect memory measure in a group of 12 organic amnesics of several aetiologies and their matched controls, tested at two delays. Both subject groups were found to copy previous seen shapes faster than new foil shapes, and the magnitude of the speed up effect did not differ significantly between amnesics and matched controls when tested at two delays of 10 min and 24 hr, respectively. The size of the indirect memory effect did not decline across the delay in either group. In contrast to indirect memory performance, measured by two-choice recognition of the shapes, was impaired in the amnesic group and there was some suggestion that recognition performance declined across the delay in both subject groups.

Adult↗

PubMed1994

Do amnesics forget faces pathologically fast?

In 1978, Huppert and Piercy introduced a general method for comparing forgetting rates across groups differing in their baseline memory performance. The method has since become a standard for measuring rate of forgetting in amnesia. Using this method, amnesic subjects with presumed damage to midline diencephalic structures have consistently been reported to forget at a normal rate whereas patients with medial temporal lobe damage have sometimes been reported to forget pathologically fast. Conclusions about amnesic forgetting rates using Huppert and Piercy's procedure, however, are unsafe because the matching procedure results in the shortest mean item-presentation-to-test delay being longer in amnesics than control subjects. A further problem with previous work is that frequently the shortest delay at which performance is measured is 10 minutes. An alternative procedure to Huppert and Piercy's is outlined which eliminates the matching confound. An experiment was carried out using this procedure with face stimuli, and with amnesic and control performance matched immediately following study, and then tested at delays of 5, 12, and 30 minutes. Pathologically fast forgetting was observed in a group of 19 amnesics over the first 5 minutes, but between 12 and 30 minutes their controls forgot faster so that the two groups had forgotten the same amount after 30 minutes. A subgroup of nine Korsakoff patients, with probable damage to midline diencephalic structures, showed a similar abnormal forgetting pattern to the remaining 10 amnesics, some of whom had medial temporal lobe damage. A retroactive interference condition was also included for the 12 minute condition at which delay patient and control recognition was mildly and equivalently disrupted. For unknown reasons perhaps related to a storage abnormality, amnesics lose face recognition memory sooner in the first 30 minutes of forgetting than do normal people, who show accelerated forgetting later so as to match patients after 30 minutes delay.

Adult↗

PubMed1994

New-association priming of word identification in normal and amnesic subjects.

Subjects took an implicit memory test in which pairs of unrelated words were flashed briefly and the ability to identify the second word of each pair was measured as a function of prior study. In young subjects, identification was better when the second word had been studied compared to when it had not been studied (word-specific priming). Identification was also better when the two words had been paired at study compared to when they had been studied separately (association-specific priming). In amnesic patients, word-specific priming was normal compared to that in age- and IQ-matched control subjects. Association-specific priming was observed, but it was below normal levels. This outcome suggests that the amnesic dysfunction can encompass priming of new verbal associations but spare priming of existing verbal information.

Adult↗

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

Evidence of covert recognition in a prosopagnosic patient.

This is a case-study of a patient (ET) who suffers from prosopagnosia, in the context of impairment to cognitive functions, following traumatic brain injury. Despite severe perceptual difficulties in tests involving non-face stimuli and matching unfamiliar faces, ET showed evidence of "covert" recognition of familiar faces in a number of tasks. Although densely prosopagnosic, she performed at normal levels in word and object recognition tasks, and is unimpaired in her ability to recognise names of celebrities. She performed at the same level as controls in her ability to make a forced-choice of the correct name for a famous face, even though it evoked no feeling of familiarity for her. She performed at chance in a forced-choice face familiarity decision task, but showed evidence of covert recognition in a "true" versus "untrue" face-name learning task. ET showed overt recognition of some famous faces using a procedure based on Sergent and Poncet's (1990) semantic activation task. The pattern of impairment of ET's face processing abilities is interpreted in terms of an interactive activation model of face processing.

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↗

PubMed1994

No selective deficit in recall in amnesia.

Are amnesic patients selectively impaired in recall relative to recognition? Experiment 1 studied a group of Korsakoff amnesics and matched the amnesic level of recognition with that of control subjects by testing control recognition of unrelated words after longer delays. It was found that under these conditions the observed levels of recall were also approximately equal. In Experiment 2, a similar result occurred when the Korsakoff amnesic level of recognition for unrelated words was matched by varying the number of presentations as well as delay before testing. In Experiment 3, a similar result occurred again with a group of amnesics of mixed aetiology and recognition levels for related words matched by varying the duration of presentation and delay before testing. In this experiment, both recognition and recall of the same items were assessed. It was found that for the amnesic group the observed level of dependency between recognition and recall was less than that for the control group. One possible interpretation of this result is that the microstructure of the recall process may be selectively disturbed in amnesia. The principal finding, however, is that in all three experiments there was no significant evidence of the existence in amnesia of a selective deficit in the overall level of recall relative to that of recognition.

Adult↗

PubMed1993

Encoding ability is preserved in amnesia: evidence from a direct test of encoding.

The encoding ability of 17 amnesics of mixed aetiology and 17 matched normal controls was assessed directly using a novel procedure. On two separate occasions, subjects were shown 60 complex drawings each containing six pictures. On one occasion each drawing was shown for 6 sec, and on the other occasion it was shown for 25 sec. Immediately after presentation of each drawing subjects were asked a single unpredictable question about picture colours, location, size or semantic category. Amnesics performed normally in the 6-sec exposure condition indicating that all of the tested kinds of information were encoded at a normal rate. Performance in this condition correlated with short-term, but not long-term memory in the amnesics indicating that it depended largely on encoding and short-term memory. However, the amnesics were impaired in the 25-sec condition where performance should have depended on (long-term) memory abilities at which they were impaired. The results are inconsistent with available encoding deficit accounts of amnesia.

Adult↗

PubMed1993

Preserved pattern completion priming for novel, abstract geometric shapes in amnesics of several aetiologies.

Two experiments were conducted using a paradigm developed by Gabrieli et al., Neuropsychologia 28, 417-427, 1990, which assessed both indirect and direct memory performance in a completion task for novel abstract geometric patterns. The preferred method of scoring was the lines method, based on the number of correct and incorrect lines produced for each item. It was chosen because it is both the simplest and the most informative measure. Two methods of scoring were used in previous work, namely, the strict whole figure method and the lenient whole figure method (Gabrielli et al., 1990; Verfaelie et al., Brain Cognit. 18, 34-45, 1992). Therefore to facilitate comparisons between studies and to determine the characteristics of different scoring methods, results with all three measures were included. In Experiment 1, two different encoding strategies of naming and copying were used in order to explore the relationship between indirect and direct memory performance. Indirect memory performance in the naming condition was at baseline whereas in the copying condition it was significantly above baseline. Cued recall did not differ across encoding conditions but recognition was higher in the naming condition than the copying condition. In Experiment 2, an attempt was made to extend the findings of two studies, one with H.M. (Gabrielli et al., 1990) and one with nine Korsakoffs (Verfaelie et al., 1992), to a larger group of 14 amnesics of several aetiologies. Indirect memory performance was found to be equivalent for the amnesics and their matched controls, only when the lenient and the lines methods of scoring were used. Recognition and cued recall performance was impaired for the amnesics compared to the controls.

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

Preservation of priming for interactive context in amnesics.

The performance of a group of 12 amnesics of mixed aetiology was compared with that of two groups of normal subjects on a priming task in which subjects' spontaneous definitions of homonyms were biased in accordance with the sense of interactive context words which had earlier been shown with the homonyms. The amnesics showed significant and normal levels of interactive context priming even when the amount of attention paid to the interactive context words was minimized during training. Reducing the amount of attention paid to the context words during training did, however, decrease the amount of priming, shown by both groups of subjects, to the same degree. It also decreased recognition of trained homonym-context word pairs to a similar extent in amnesics and normal people. In an additional condition of the study, it was shown that normal subjects were aware of the meaningful relationship between homonyms and context words even when the amount of attention they paid to context words was minimized during training. Priming seemed to be stochastically independent of recognition and was also unrelated to signs of frontal lobe damage, intelligence or explicit memory. All three groups of subjects showed similar and significant levels of priming regardless of whether or not only definitions that made no direct reference to the context words were scored. It was concluded that amnesics have preserved priming for interactive context words that are encoded with low levels of attention even though there is evidence that they have a disproportionate recognition deficit for this kind of information under these conditions. The theoretical implications of the results are discussed.

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 incidental spatial-memory and recall deficits in amnesia.

Seventeen amnesics, including patients with Korsakoff's disease, post-encephalitic amnesia and amnesia caused by rupture of an anterior communicating artery aneurysm, were compared with 17 matched control subjects on a task in which 16 nameable shapes were placed on different squares of a 49-square grid. One version of the task tapped free recall and recognition of the shapes and a second version tapped three forms of spatial memory. The patients were tested after more learning opportunity and shorter delays than were the controls so as to match their recognition levels. Under these conditions, the amnesics performed worse than the controls on free recall, location-to-target memory, target-to-location memory and possibly on non-associative spatial memory although this was less impaired than target-to-location memory. Each of the main aetiological subgroups showed these disproportionate deficits to an apparently similar degree. The disproportionate free recall deficit was unrelated to the spatial memory deficits and overall severity of amnesia, and was associated with ageing and signs of frontal lobe dysfunction. The disproportionate spatial memory deficits were unrelated to frontal lobe dysfunction, but the target-to-location memory measure was associated with impairments of recognition and recall of target material. The results are broadly consistent with the context-memory deficit hypothesis of 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

Increased reading speed for words and pronounceable non-words: evidence of preserved priming in amnesics.

Twelve amnesics with various aetiologies were compares with 12 matched control subjects on a task which examined the increase in reading speed for lists of words and pronounceable non-words that were shown several times and read twice during a training phase. After a four minute delay the reading speed for the primed lists was compared with that for an equal number of umprimed lists. No non-specific practice effects were observed. The amnesics showed an equal proportional increase in reading speed for primed words list to that of their controls, and, if anything, a slightly greater reading speed increase for non-words. These effects were found even when an amnesic subgroup, selected because its baseline reading speed was closely matched to that of the controls, was used for the comparison. The patients' preserved priming for the novel information found in the non-word list reading task occurred in conjunction with very impaired free recall for the contents of the lists. The effects occurred in patients of all aetiologies used in the study and confirm and extend the findings of Moscovitch, Winocur and McLachlan (1986).

Alcohol Amnestic Disorder↗

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↗