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T Shallice

Publications and source records attributed to T Shallice.

9 recordsLinked to original sources
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

Lesioning an attractor network: investigations of acquired dyslexia.

A recurrent connectionist network was trained to output semantic feature vectors when presented with letter strings. When damaged, the network exhibited characteristics that resembled several of the phenomena found in deep dyslexia and semantic-access dyslexia. Damaged networks sometimes settled to the semantic vectors for semantically similar but visually dissimilar words. With severe damage, a forced-choice decision between categories was possible even when the choice of the particular semantic vector within the category was not possible. The damaged networks typically exhibited many mixed visual and semantic errors in which the output corresponded to a word that was both visually and semantically similar. Surprisingly, damage near the output sometimes caused pure visual errors. Indeed, the characteristic error pattern of deep dyslexia occurred with damage to virtually any part of the network.

Brain↗
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↗
PubMed1979

Semantic access dyslexia.

An analytical investigation of the residual reading capacities of a single patient with dyslexia without dysgraphia is reported. Both his ability to name and to comprehend letters and words were severely impaired. The major finding of this investigation was AR's striking capacity for categorizing words he could not read. In addition there was evidence of semantic priming effects. Thus AR was frequently able to achieve partial comprehension of words he could not read. The orthodox interpretation of the dyslexia without dysgraphia in terms of a disconnection syndrome is shown to be inappropriate, at least for the present case, where the deficit appears to be within the semantic domain; it is argued that this type of dyslexia is due to an impairment in accessing semantic information.

Auditory Perception↗
PubMed1978

The involvement of the frontal lobes in cognitive estimation.

Ninety-six patients with localised cerebral lesions were tested on a task of providing reasonable answers to Cognitive Estimate questions. These questions are ones that can be answered using general knowledge available to almost all subjects, but for which no immediately obvious strategy is available. It was found that patients with frontal lesions gave significantly more bizarre answers than patients with more posterior lesions. This effect is interpreted in terms of Luria's (1966) theory of the planning functions of the frontal lobes.

Adult↗