1,721,063 research outputs found
The domain of supervisory processes and temporal organization of behaviour
No full textThe possibility that the supervisory system of Norman and Shallice (1986) can be fractionated into different subprocesses is discussed. It is argued that confronting a novel situation effectively requires a variety of different types of process. It is then argued that evidence of separability of different processes may be obtained by the observation of very low correlations across patients on more than one measure on each of which frontal patients show a performance deficit. Examples of this are provided by examining the Hayling sentence completion and the Brixton spatial anticipation tasks. Finally, differential localization of the subprocesses and hence the conclusion that they are separable is discussed with respect to the localization of monitoring and verification processes in memor
Supervisory control of thought and action
No full text1. Perception: selection and attention ; 2. Attentional control of complex tasks ; 3. Conscious awareness ; 4. Attention, arousal, and stres
Deficits in strategy application following frontal lobe damage in man
No full textA 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
Can the neuropsychological case-study approach be applied to schizophrenia?
No full textNeuropsychological 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
Selective impairments in self-ordered working memory in a patient with a unilateral striatal lesion
No full textA patient is described with a striatocapsular infarct resulting in damage to the left caudate-putamen, sparing the left ventral striatum and globus pallidus, who exhibits relatively selective deficits in self-ordered working memory performance. These deficits were shown repeatedly over several months, with several different types of test and material. The impairments were shown in the absence of obvious perceptual, visuospatial constructional, motor or language deficits. Recognition memory and cued recall performance was intact, although free recall was poor on some occasions. Aspects of executive performance were also intact, including set-shifting performance, but there were significant deficits in planning. The results are discussed in terms of the operation of parallel, functionally segregated cortico-striatal ‘loops’. © 1995, Taylor & Francis Group, LLC. All rights reserved
The origins of utilization behaviour
No full textUtilization 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 placed 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
Typical and atypical functional specialisation within human prefrontal cortex
Full text linkThe prefrontal cortex (PFC) plays an important role in a range of higher-level cognition including decision-making, social cognition, executing delayed intentions, and creative thinking. Previous studies have proposed a functional specialisation of the PFC region, and that this heterogeneity is associated with both structural and functional typicality between individuals. In order to examine this possibility, a reverse engineering approach was used to develop a PFC battery measuring behaviours relating to gambling, referential judgment, mentalizing, and faux pas detection. 107 typical-developing (TD) adults were recruited to establish the behavioural baseline, and identify the neural correlates of the measures in the PFC battery using voxel-based morphometry (VBM). The VBM analysis revealed significant relationships between different mental abilities and the size of different PFC sub-regions. Subsequently, 34 adults with autism spectrum disorder (ASD; a pathological group diagnosed with deficits on decision-making and social cognition) were tested on the new PFC battery. The results show that it provides new tools for detection of the ASD phenotype, and demonstrated the atypicality of ASD subjects when using single-case analysis. The thesis then turned to the functional specialisation of rostral PFC. A dissociation between lateral vs. medial rostral PFC activation was revealed when executing delayed intentions (the ability referred as prospective memory, or PM), compared with baseline ongoing activities. A novel PM paradigm for use with fMRI was designed to examine the specificity of PM cues. The results demonstrated the role that BA9/46 region plays in the detection of certain vs. uncertain future intentions. The final study examined cross-cultural differences in creativity, a cognitive ability thought to be substantially underpinned by frontal lobe structures. Matched adults from the UK and Taiwan were compared on adapted version of standard measures of creativity. Cross-cultural differences were found on the novelty aspect of the creativity, but not on the usefulness aspect, which seemed to reflect different Eastern vs. Western self-construal. Altogether, the thesis used a range of approaches to highlight functional and structural variation within the PFC region and the mental abilities it supports, demonstrating some principles of organisation that exist across individuals, but also differences between individuals, and between populations of individuals
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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