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Biomedical subjects

P W Burgess

Publications and source records attributed to P W Burgess.

16 recordsLinked to original sources
PubMed2005

Prolonged cognitive dysfunction in survivors of critical illness.

A prospective study using neuropsychological testing explored cognitive performance, and specifically executive function, in survivors of critical illness during the first year of recovery. Fifty-one patients who had survived 3 days or more in the intensive care unit were studied approximately 3 months after discharge; 45 of them were studied again 6 months later. General health was assessed using the Short-Form 36. Cognitive and executive functions were measured using Raven's Progressive Matrices, the Hayling Sentence completion test and the Six-Element Test. Three months after discharge from intensive care, all eight domains of Short-Form 36 were impaired among survivors; by 9 months, four of the eight domains showed significant improvement. At 3 months, 35% of patients scored at or below a level equivalent to the lowest performing 5% of a normal population (i.e. the fifth percentile) on two or more tests of cognitive function; by 9 months only 4% of patients were impaired to this extent. Although cognitive performance improved with time, it remained below normal.

Adult↗
PubMed2001

Brain regions involved in prospective memory as determined by positron emission tomography.

Prospective memory (PM) refers to the functions that enables a person to carry out an intended act after a delay. Despite the ubiquity of this behaviour, little is known about the supporting brain structures and the roles that they play. In this study, eight healthy participants performed four different PM tasks, each under three conditions: a baseline, and two conditions involving an intention. In the first of the intention conditions, subjects were asked to make a novel response to a certain class of stimuli whilst performing an attention-demanding task. However, the expected stimuli never actually occurred. In the second intention condition subjects were expecting to see these stimuli as before, and they did occur on approximately 20% of trials. Relative to the baseline condition, increases in regional cerebral blood flow (rCBF) as estimated by oxygen-15 positron emission tomography technique across all four tasks were seen in the frontal pole (Brodmann's area 10) bilaterally, right lateral prefrontal and inferior parietal regions plus the precuneus when subjects were expecting a PM stimulus regardless of whether it actually occurred. Further activation was seen in the thalamus when the PM stimuli occurred and was acted upon, with a corresponding rCBF decrease in right lateral prefrontal cortex. It is argued that the first set of region play a role in the maintenance of an intention, with the second set involved additionally in its realisation.

Adult↗
PubMed2000

Strategy application disorder: the role of the frontal lobes in human multitasking.

Strategy application disorder is a term used to describe a pattern of deficits, usually associated with frontal lobe dysfunction, where people show disorganisation, absentmindedness and problems with planning and decision making in everyday life despite normal performance on traditional neuropsychological tests. It is argued that the prototypical situation which presents problems for these cases are those which require multitasking, and although good cases are rare in the literature, those that do exist show a characteristic neuropsychological pattern. Moreover, this pattern is confirmed in recent group studies of multitasking and of the relationship between multitasking tests (such as the Six Element Test), failures in everyday life and other neuropsychological measures. At present the evidence suggests that the potential frontal brain regions most implicated in multitasking are the anterior cingulate; B.A. 10 and immediately adjacent areas; and the right dorsolateral prefrontal cortex, with each making a unique contribution to different aspects of performance. Furthermore, recent studies show striking dissociations between performances on multitasking tests and two of the most commonly administered measures of executive function: the verbal fluency test and the Wisconsin Card Sorting Test, which sets a minimum level for a fractionation of the executive syndrome in humans.

Attention↗
PubMed2000

The cognitive and neuroanatomical correlates of multitasking.

Patients who show the "strategy application disorder" can show deficits restricted to situations requiring multitasking, but the precise neuroanatomical and cognitive correlates of this problem have been rarely investigated. In this study, 60 people with circumscribed cerebral lesions and 60 age- and IQ-matched controls were given a multitasking procedure which allowed consideration of the relative contributions of task learning and remembering, planning, plan-following and remembering one's actions to multitasking performance. Lesions to the left posterior cingulate and forceps major regions gave deficits on all measures except planning. Remembering task contingencies after a delay was also affected by lesions in the region of the left anterior cingulate, and rule-breaking and failures of task switching were additionally found in people with lesions affecting the medial and more polar aspects of Brodmann's areas 8, 9 and especially 10. Planning deficits were associated with lesions to the right dorsolateral prefrontal cortex (RDLPFC). A theory of the relationships between the cognitive constructs underpinning multitasking was tested using structural equation modelling. The results suggest that there are three primary constructs that support multitasking: retrospective memory, prospective memory, and planning, with the second two drawing upon the products of the first. It is tentatively suggested that the left anterior and posterior cingulates together play some part in the retrospective memory demands, while the prospective memory and planning components make demands on processes supported by the left areas 8, 9 and 10 and the RDLPFC respectively.

Adolescent↗
PubMed1999

Content-specific confabulation.

This report describes a person who confabulated following an anterior communicating artery aneurysm. His confabulation was limited to one very circumscribed area of his life and remained stable for twelve weeks, eventually improving with rehabilitation. It is argued that a content-specific confabulation of this nature challenges current theories of confabulation, and an integrative explanation is given based on previous findings by Burgess and Shallice (1996b) of the mechanisms of autobiographical recollection in healthy people.

Cognition Disorders↗
PubMed1998

The ecological validity of tests of executive function.

Ninety-two mixed etiology neurological patients and 216 control participants were assessed on a range of neuropsychological tests, including 10 neuropsychological measures of executive function derived from 6 different tests. People who knew the patients well (relatives or carers) completed a questionnaire about the patient's dysexecutive problems in everyday life, and this paper reports the extent to which the tests predicted the patients' everyday life problems. All of the tests were significantly predictive of at least some of the behavioral and cognitive deficits reported by patients' carers. However, factor analysis of the patients' dysexecutive symptoms suggested a fractionation of the dysexecutive syndrome, with neuropsychological tests loading differentially on 3 underlying cognitive factors (Inhibition, Intentionality, and Executive Memory), supporting the conclusions that different tests measure different cognitive processes, and that there may be limits to the fractionation of the executive system.

Adult↗
PubMed1996

Response suppression, initiation and strategy use following frontal lobe lesions.

Ninety-one patients with cerebral lesions were tested on a task involving two conditions. In the first condition (response initiation) subjects were read a sentence from which the last word was omitted and were required to give a word which completed the sentence reasonably. In the second condition (response suppression) subjects were asked to produce a word unrelated to the sentence. Patients with frontal lobe involvement showed longer response latencies in the first condition and produced more words which were related to the sentence in the second, in comparison to patients with lesions elsewhere. Moreover, in the second condition patients with frontal lobe lesions produced fewer words which showed the use of a strategy during response preparation. Performance on the initiation and suppression conditions was unrelated at the group or single case level. The relationship between response initiation, suppression and strategy use are discussed.

Adolescent↗
PubMed1996

Bizarre responses, rule detection and frontal lobe lesions.

Seventy-seven patients with different cerebral lesions were tested on a rule-detection task where the stimuli were designed in such a way as to minimize the activation of pre-existing schemata. Patients with lesions involving the frontal lobes were poorer at achieving set than patients with lesions elsewhere. In addition, the anteriorly-lesioned group showed a greater tendency to guess and were more likely to abandon a correct rule once it had been attained, but there were no differences between the groups in incidence of perseverative responses. Various plausible explanations of these results are examined, with the most favoured account suggesting that anterior patients show an exaggerated willingness to adopt bizarre hypotheses.

Adult↗
PubMed1996

Confabulation and the control of recollection.

It is argued that current models of memory do not adequately account for the confabulations that are found in the recall of certain neurological patients. A model of the relation between control processes and memory involved in recalling autobiographical episodes is put forward. It is based on detailed analysis of the protocols of healthy volunteers' autobiographical recollections of recent everyday events. It is held that damage to different components of the model fits with the different patterns of performance found in confabulators, and examples of the errors that confabulators make are discussed in terms of those made by normal subjects.

Cognition Disorders↗
PubMed1993

Unilateral frontal lobectomy can produce strategy application disorder.

Following a 5 cm left frontal lobectomy for the removal of a mixed astrocytoma-oligodendroglioma, a 51 year old right handed man showed a marked dissociation between his performance on standard neuropsychological tests and his everyday behaviour. In contrast to his intact neuropsychological test performance, he was impaired on a test of "strategy application" which requires goal articulation, plan specification, self-monitoring, and evaluation of outcomes, as well as the establishment of mental "markers" to trigger specific behaviour. Strategy application disorder can therefore be produced by a unilateral circumscribed frontal lobe lesions.

Anger↗
PubMed1991

Can the neuropsychological case-study approach be applied to schizophrenia?

Neuropsychological studies of schizophrenia typically apply a small number of tests to a large group of patients. This approach has at least two drawbacks. First, the heterogeneity of the condition will lead to group means which may not reflect the behaviour of any individual. Secondly, it is difficult to infer the nature of the underlying cognitive impairments from a small number of tests, since good performance on a particular test depends on many different cognitive processes. In these circumstances it is more appropriate to apply the methods of cognitive neuropsychology where a large number of tests are used on a single case. This approach has proved fruitful in the study of neurological patients. We have intensively studied 5 chronic schizophrenic patients. These patients varied greatly in terms of overall ability. However, all patients, whatever their overall ability, performed badly on tests sensitive to frontal lobe lesions. This result suggests impairment of the supervisory attentional system in these patients. In addition, one patient suffered from a visual agnosia.

Adult↗
PubMed1991

Deficits in strategy application following frontal lobe damage in man.

A quantitative investigation of the ability to carry out a variety of cognitive tasks was performed in 3 patients who had sustained traumatic injuries which involved prefrontal structures. All 3 had severe difficulties in 2 tests which required them to carry out a number of fairly simple but open-ended tasks over a 15-30 min period. They typically spent too long on individual tasks. All patients scored well on tests of perception, language and intelligence and 2 performed well on a variety of other tests of frontal lobe function. Explanations for their difficulty on the multiple subgoal tasks in terms of memory or motivational problems could be excluded. It is argued that the problem arose from an inability to reactivate after a delay previously-generated intentions when they are not directly signalled by the stimulus situation.

Accidents, Traffic↗
PubMed1989

The origins of utilization behaviour.

Utilization behaviour has previously been described clinically by Lhermitte (1983). An experimental investigation is reported of utilization behaviour in a patient with a localized inferior medial bifrontal lesion. The patient picked up and used irrelevant objects not only when place directly in front of him--the procedure developed by Lhermitte--but also when he had been instructed to carry out other tasks and his attention had not been directed to the objects. The behaviour occurred most frequently in the brief intervals between tasks, and more often when auditory-verbal rather than visuomotor tasks were being performed. The results are interpreted within an information-processing model of frontal lobe function. A differentiation is made between two forms of utilization behaviour--an 'incidental' form, as exhibited by the patient, and an 'induced' form where it occurs only when Lhermitte's procedure is adopted.

Behavior↗
PubMed1987

Behavioral treatment of attention deficits in mentally impaired subjects.

This paper describes an operant approach to the remediation of the behavioral aspects of attention deficits in three mentally impaired subjects. Two of the subjects also displayed severe atypical psychiatric disorders. Contingent reinforcement within an ABAC experimental design was used to increase levels of attending behavior. The efficacy of this approach within a group setting was demonstrated. Results suggest that some forms of additional deficit may be treated behaviorally despite differing etiologies of the cognitive deficit. The implications for occupational therapy are discussed within the context of the design of the ward program.

Adolescent↗