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Biomedical subjects

A G Canavan

Publications and source records attributed to A G Canavan.

11 recordsLinked to original sources
PubMed1991

Slow cortical potentials (SCPS) in schizophrenic patients during performance of the Wisconsin card-sorting test (WCST).

Fifteen schizophrenic patients (diagnosed according to DSM-III-R) and 15 age- and education-matched controls were tested on a computerized version of the Wisconsin card-sorting test (WCST). Slow Cortical Potentials (SCPs) were recorded throughout the performance from frontal, central and parietal electrode sites. As expected, the patients were impaired on the WCST, achieving fewer categories overall and incurring significantly more "unique" errors, although they were not significantly more perseverative than the controls. The patients did not display a generalized impairment in SCPs, differences between the groups emerging only before presentation of the key-cards and after presentation of the feedback regarding the correctness of the response. Neither the choice-card at the beginning of the trial, nor the presentation of the key-cards resulted in attenuated Evoked Potentials (EPs) in the patients. The lack of any abnormality in EPs suggests that the reason for the poor performances of schizophrenic patients on the WCST lies elsewhere than in perceptual stimulus processing. Contrary to expectations no specific impairment in frontal SCPs was detected.

Adult↗
PubMed1990

Prism adaptation and other tasks involving spatial abilities in patients with Parkinson's disease, patients with frontal lobe lesions and patients with unilateral temporal lobectomies.

Patients in the early stages of Parkinson's disease were compared with patients who had sustained damage specific to either the frontal or temporal lobes and normal controls on a delayed alternation task, a test of the left right orientation and a prism adaptation task. On the former two tasks age accounted for more of the variability in performance than did site of brain lesion. However, patients with frontal lobe, right temporal lobe or basal ganglia damage were significantly impaired on the adaptation task. The results are discussed with regard to "switching", "sequencing" and "internal guidance" of movement hypotheses.

Adult↗
PubMed1989

Motor learning in monkeys (Macaca fascicularis) with lesions in motor thalamus.

The study examines the nature of the influence that the basal ganglia exert on frontal cortex via the motor nuclei of the thalamus. Twelve monkeys were trained to pull a handle given one colour cue and to turn it given another. Bilateral lesions were then placed in the ventral thalamus. Four monkeys with large anterior lesions including the VA nucleus and the anterior part of VLo were severely impaired at relearning the task. Monkeys with small lesions in VAmc or with lesions centred on VLo were not impaired. The analysis of the histology suggests that the impairment in the four monkeys did not result from involvement of the cerebellar relay through nucleus X. It is argued that the animals are not impaired because of faulty execution. This suggests that the basal ganglia have an influence on motor learning.

Animals↗
PubMed1989

Sequence ability in parkinsonians, patients with frontal lobe lesions and patients who have undergone unilateral temporal lobectomies.

Patients in the early stages of Parkinson's disease were compared with patients who had sustained damage specific to either the frontal or temporal lobes and normal controls on a number of sequencing tests. These tests involved the reproduction of sequences of hand gestures, sequences tapped out on blocks, and sequences of digits. Only the groups with frontal lobe lesions or right temporal lobectomies were impaired on any of these tasks, though no group was impaired on all of the sequencing tasks.

Adolescent↗
PubMed1989

The performance on learning tasks of patients in the early stages of Parkinson's disease.

It is known that in animals learning is disrupted by caudate lesions; but there has been no agreement about whether pathology in the basal ganglia causes a similar impairment in man. Nineteen patients in the early stages of Parkinson's disease were tested on two associative learning tasks and on the Wisconsin Card Sorting Task; and their performance was compared with that of patients with frontal or temporal lobe lesions. On the two associative learning tasks there was no overall difference between the Parkinsonian group and the controls. However, a minority of the Parkinsonian patients performed very poorly on these tasks; and it was noted that these tended to be the older patients.

Adult↗
PubMed1989

Cognitive mapping after unilateral temporal lobectomy.

An investigation of the extension of O'KEEFE and NADEL's [The Hippocampus as a Cognitive Map. Oxford University Press, Oxford 1978] theory of hippocampal functioning is described in patients who have undergone unilateral temporal lobectomy for the relief of epilepsy. A new spatial task, incorporating a recall-for-designs test but based on studies of spatial memory and cognitive mapping in animals was devised. Results supported the prediction of temporal lobe structure involvement in the mediation of non-egocentric but not egocentric space, and of the role of right temporal lobe structures in conditions designed to encourage "place" but not "cue" learning strategies. The role of verbal mediation in task performance is also discussed.

Adolescent↗
PubMed1989

Classical conditioning in patients with severe memory problems.

Classical conditioning is one of the most fundamental forms of learning, and yet little is known regarding the effects of brain injury on conditioning processes in humans. Three patients with temporal lobe lesions and severe memory problems were therefore assessed in terms of eyeblink conditioning, extinction, discrimination and reversal learning, and in one patient electrodermal conditioning was also investigated. The acquisition of conditioned responses was seen to be intact, but the evidence regarding extinction was ambiguous. All of the patients were impaired in discrimination learning and also reversal learning.

Adult↗
PubMed1988

Verbal and abstract designs paired associate learning after unilateral temporal lobectomy.

The combined use of a new abstract designs Paired Associates test with the Verbal Paired Associates test of Form 1 of the Wechsler Memory Scale was investigated with respect to eliciting material specific memory deficits after unilateral temporal lobectomy. Although the verbal test differentiated between the memory ability of these two groups more clearly than the abstract designs test, the effectiveness of looking at the difference between total scores on the two tests was demonstrated. The two tests produced similar levels of performance in control subjects.

Analysis of Variance↗
PubMed1987

Lateralisation of memory functions in epileptic patients by use of the sodium amytal (Wada) technique.

Lateralisation of speech and memory functions was determined in 27 patients, being assessed for surgical treatment of unilateral temporal lobe epilepsy, using the sodium amytal procedure. The most common outcome with regard to language was the retention of normal left hemisphere dominance, regardless of handedness or side of lesion. In contrast, memory functions were most often to be found only in the unaffected hemisphere, also regardless of handedness or side of lesion. A lesion of either hemisphere appeared capable of interfering with language and verbal memory functions in an unexpectedly high proportion of patients.

Adolescent↗
PubMed1985

Luria's frontal lobe syndrome: psychological and anatomical considerations.

Luria has described a syndrome of disinhibited and impulsive behaviour, in which the patient is unable to follow sequential instructions. This he attributes to localised frontal lobe damage. However, group studies of patients with focal lesions of the frontal lobes fail to reveal such a syndrome. A patient is described who displayed a form of Luria's syndrome temporarily. Psychometric and post mortem evidence indicate that the syndrome arises only under conditions of more global cerebral dysfunction.

Brain↗