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Biomedical subjects

J Doyon

Publications and source records attributed to J Doyon.

31 records · Page 2Linked to original sources
PubMed1996

Planning and spatial working memory: a positron emission tomography study in humans.

Previous work with both neurosurgical and neurodegenerative patient groups has suggested that high level planning is mediated by neural circuitry which includes both the prefrontal cortex and the striatum. In this study, the functional anatomy of cognitive planning was investigated further, using positron emission tomography (PET). Regional cerebral blood flow (rCBF) was measured in 12 normal volunteers while performing easy and difficult versions of (i) a modified Tower of London planning task; (ii) a mnemonic variant of this task that required short-term retention and reproduction of problem solutions; and (iii) a control condition that involved identical visual stimuli and motor responses. Significant increases in rCBF were observed in the left hemisphere, in both the mid-dorsolateral frontal cortex and in the head of the caudate nucleus, when the difficult planning task was compared with the control condition. Moreover, subtraction of a simple planning condition from the more difficult one revealed focal increases in rCBF in the caudate nucleus and the thalamus only. During both mnemonic variants of the planning task, changes were also observed in the mid-dorsolateral frontal cortex and in more ventral frontopolar regions, bilaterally. When compared directly, the planning and memory conditions differed in terms of these ventral activation foci, but not in the pattern of activation observed in mid-dorsolateral frontal cortex. These findings further implicate frontostriatal circuitry in high-level planning and provide evidence for functionally distinct contributions from ventral and dorsolateral frontal regions to spatial working memory.

Adult↗
PubMed1996

Functional anatomy of visuomotor skill learning in human subjects examined with positron emission tomography.

The present study was designed to examine patterns of regional cerebral blood flow (CBF) associated with the learning of a repeated visuomotor sequence both in the early and late phases of the acquisition process. In addition, changes in blood flow related to the implicit versus explicit aspects of learning such a skill were investigated. Fourteen normal control subjects were scanned while performing the task (i) in both early and advanced learning stages of the visuomotor sequence; (ii) after having acquired explicit knowledge of the sequences; and (iii) in two control conditions (perceptual and random sequence). Subtraction of the random condition from the highly learned condition revealed specific areas of activity in the right ventral striatum and dentate nucleus of the cerebellum. Blood flow changes in the right hemisphere were also seen in the medial posterior parietal and prestriate regions, as well as in the anterior cingulate cortex. Finally, once the subjects had acquired explicit knowledge of the embedded sequence that was presented in the highly learned condition, increased CBF activity was observed only in the mid-ventrolateral frontal area in the right hemisphere. These findings confirm that both the striatum and the cerebellum are involved in the implicit acquisition of a visuomotor skill, especially in the advanced stages of the learning process, and furthermore that the ventrolateral prefrontal cortex contributes preferentially to the declarative aspect of this task.

Adult↗
PubMed1995

Mental representation of knowledge following frontal-lobe or postrolandic lesions.

The aims of this study were to examine the role of the prefrontal cortex in the representation of familiar activities using scripts, and to compare both Shallice's [Phil. Trans. Roy. Soc. Lond. B. Vol. 298, pp. 199-209, 1982] and Grafman's [Integrating Theory and Practice in Clinical Neuropsychology, pp. 93-138, Lawrence Erlbaum, Hillsdale, New Jersey, 1989] models of schematic representation of knowledge. Twelve patients with frontal-lobe damage, nine with postrolandic lesions, and 13 normal control subjects were asked to generate actions belonging to six different scripts in a forward condition, and to two others in a backward condition. The latter condition was included to test Shallice's hypothesis that damage to the frontal lobes would only affect the execution of non-routine tasks. The results showed that patients with frontal-lobe lesions produced scripts that were deprived of contextual elements and made more sequencing errors in the forward condition than matched normal control subjects, hence suggesting that the frontal cortex contributes to the production of an adequate mental representation of routine events. By contrast, the performance of the two clinical groups did not differ from the control subjects in their ability to generate scripts in the backward condition, although these three groups of subjects generated fewer actions in the latter condition. Further qualitative analyses demonstrated that patients with parietal-, but not with temporal-lobe lesions, produced sequencing errors in both forward and backward conditions. The latter findings suggest that the frontal lobes, together with the parietal cortex, may play a special role in establishing the spatio-temporal position of events within a script. The results of this study are discussed in terms of the recent models developed by Shallice and Grafman concerning the contribution of the frontal lobes in the mental representation of knowledge.

Adult↗
PubMed1993

[The frequent screams].

Functional analysis is a research process that links problem behavior, its surrounding elements and the resulting consequences. The goal of this study was to decrease repetitive shouting of an elderly patient diagnosed with Alzheimer-like dementia. The analysis provided the following data: BEHAVIORS: Repetitive shouting by the patient lasting 80-115 seconds per 30 minutes during specific times of the day--accompanied by licking of the lips to moisten them. Environmental factors: Constant loud noise in the patient's room; the use of loud voices by staff and visitors; familiar objects out of the patient's reach. Individual factors: Diagnosis of the patient's blindness and auditory hypersensitivity; side-effects of psychotropic medications; a lack of social activities; inactivity because of the patient being bedridden 22 hours per day and the use of restraints when positioned in a chair. SURROUNDING ELEMENTS: The patients was isolated in a private room; psychotropic medication was increased; staff and other patients were less disrupted and the number of visitors to the patient was decreased. CONSEQUENCES: The above data enabled the formulation of four hypotheses (with specific interventions for each) that assisted staff in planning the patient's care for a 10-day period; a reduction of anxiety; a reduction in discomfort; sensory hypostimulation; verbal hypostimulation. Following the application of these interventions for a 10-day period, a second set of data was gathered and the results showed a decrease in shouting by 40 per cent in the morning and 51 per cent in the afternoon.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

A congenital anomaly of vitamin B12 metabolism: a study of three cases.

The clinical and morphologic findings of three patients with metabolic acidosis, methylmalonic aciduria, and homocystinuria are presented. The clinical evolution of the patients was similar and was characterized in the first weeks of life by failure to thrive, hypotonia, and lethargy associated with pancytopenia and hepatic dysfunction, eventually progressing to severe respiratory insufficiency and renal failure consistent with a hemolytic-uremic syndrome. The patients died at 40, 45, and 75 days of age. Biochemical analyses and complementation studies revealed a congenital anomaly of vitamin B12 metabolism (cobalamin C disease). Postmortem morphologic findings in all three cases were dominated by a thrombotic microangiopathy of the kidneys and lungs, diffuse hepatic steatosis, and megaloblastic changes in the bone marrow. A severe gastritis with striking cystic dysplastic mucosal changes and total absence of parietal and chief cells was a consistent finding in all three cases, the rest of the gastrointestinal tract appearing essentially normal. Cobalamin C disease is an intracellular defect of cobalamin metabolism with possible recessive inheritance that can result in multiorgan failure early in life, with a thrombotic microangiopathy and unusual changes in the gastric mucosa.

Humans↗
PubMed1991

Right temporal-lobe contribution to global visual processing.

The performance of 92 patients with unilateral temporal- or frontal-lobe excisions and 35 normal control subjects was tested under two experimental conditions (global, local) of a Stroop-type reaction-time task, employing either hierarchically structured letters or abstract designs as stimuli. In the local condition, subjects were asked to focus their attention on the small forms and to ignore the large form, whereas they were instructed to do the reverse in the global condition. The results showed that, in the local condition, the patients with right temporal-lobe lesions were less affected than the other groups by interference from the global aspect of the stimulus. This reduced sensitivity to the overall configuration of the stimulus was unrelated to the extent of hippocampal removal or to the presence of visual-field defects. These findings support the hypothesis that the human right temporal neocortex contributes to the global processing of visual information.

Adolescent↗
PubMed1991

Role of the right temporal lobe in visual-cue learning during repeated pattern discriminations.

The ability to acquire visual cues for discriminating between two targets against a background of visually similar items was examined in 64 patients with unilateral temporal- or frontal-lobe excisions and 20 normal control subjects. The subjects were tested on two versions (letters and abstract designs) of a visual cue-learning task that was an adaptation and extension of RABBITT's (Am. J. Psychol. 80, 1-13, 1967) visual-search paradigm. For both versions, the material consisted of two packs of cards, each containing a different set of background letters or designs. Subjects were required to sort the cards into two piles according to which of two targets was present on the card. On the letter task, all groups took longer to sort when the background letters were changed after three learning trials. With abstract designs, patients with right temporal-lobe lesions failed to show this interference effect after three learning trials, but they, like other groups, did so after six. This slowness in learning was related neither to the extent of hippocampal removal nor to visual-field defects. It is argued that the right temporal neocortex plays a role in incremental learning of visual cues during repeated pattern discriminations.

Adolescent↗
PubMed1985

Biofeedback control of migraine headaches: a comparison of two approaches.

In order to assess the relative effectiveness of finger warming and temporal blood volume pulse reduction biofeedback in the treatment of migraine, 22 female migraine patients were assigned to one of three experimental conditions: temporal artery constriction feedback, finger temperature feedback, or waiting list. Biofeedback training consisted of 12 sessions over a 6-week period. All patients completed 5 weeks of daily self-monitoring of headache activity (frequency, duration, and intensity) and medication before and after treatment. Treatment credibility was assessed at the end of Sessions 1, 6, and 12. Results showed that temporal constriction and finger temperature biofeedback were equally effective in controlling migraine headaches and produced greater benefits than the waiting list condition. Power analyses indicated that very large sample sizes would have been required to detect any significant differences between the two treatment groups. No significant relationships were found between levels of therapeutic gains and levels of thermal or blood volume pulse self-regulation skills. Likewise, treatment outcome was not found to be related to treatment credibility. Further analyses revealed that changes in headache activity and medication were associated with changes in vasomotor variability. Because blood volume pulse variability was not significantly affected by biofeedback training, questions about its role in the therapeutic mechanism are raised.

Adult↗
PubMed1983

Blood volume pulse biofeedback in the treatment of migraine headache: a controlled evaluation.

In order to evaluate the specific effects of blood volume pulse (BVP) biofeedback in the treatment of migraine headaches, 21 female migraine patients were randomly assigned to one of three experimental conditions: temporal artery constriction feedback, temporal artery dilation feedback, or waiting list. Biofeedback training consisted of 15 sessions over an 8-week period. All patients completed 5 weeks of daily self-monitoring of headache activity and medication before and after treatment. Results showed that constriction and dilation biofeedback were equally effective in controlling migraines and produced greater benefits than the waiting-list condition. No significant relationships were found between therapeutic gains and BVP self-regulation skills. However, further analyses revealed that changes in headache activity and medication were associated with changes in vasomotor variability. The current rationale for the use of BVP biofeedback in the treatment of migraine is questioned and a new one is proposed.

Adolescent↗
PubMedDate not supplied

New cytotoxic analogues of annonaceous acetogenins.

A series of new acetogenin analogues incorporating a central catechol moiety instead of the tetrahydrofuran ring(s) have been prepared and tested against L1210 leukemia cells. Although less potent than bullatacinone, which has the same terminal lactone, these compounds display interesting cell cycle effects.

4-Butyrolactone↗