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Biomedical subjects

K Claeys

Publications and source records attributed to K Claeys.

6 recordsLinked to original sources
PubMed2000

The effect of cognitive load on saccadic eye movements.

The present study tested the hypothesis that, unlike prosaccades, antisaccades require controlled processing, due to the prepotent response that needs to be inhibited. The effect of the Random time Interval Generation (RIG) task (Vandierendonck, A., De Vooght, G., & Van der Goten, K. (1998). European Journal of Cognitive Psychology, 10, 413-444) on these saccade latencies and errors was studied. This task has the advantage that it loads executive processes, with only minimal interference with verbal or visuo-spatial components. A first experiment compared saccade performance within the prosaccade and the antisaccade task, executed alone and in combination with the RIG task and fixed tapping (added to exclude possible motor component interference explanations). A second experiment investigated the influence of task characteristics on the effects found. Although it was shown that antisaccades are more prone to interference of an executive interference task, it seems that prosaccades are also vulnerable. Interference on prosaccades could originate from a controlled execution of these saccades. A third experiment confirmed that endogenously generated prosaccades are susceptible to dual-task interference and showed that controlled saccade execution, without the need to inhibit a prepotent response, is sufficient to produce interference.

Adult↗
PubMed1996

[Excision of a parathyroid adenoma of the aorto-pulmonary window under thoracoscopy].

OBJECTIVES: Neck exploration is usually required in all cases of primary hyperparathyroidism. Without a precise localization preoperatively cervicotomy may be unsuccessful, especially in case of an ectopic adenoma. CASE REPORT: A patient with primary hyperparathyroidism due to a solitary adenoma localized in the middle mediastinum was identified on preoperative computed tomography and technetium-99m-sestamibi radionuclide scan. The tumor was successfully removed at thoracoscopy without neck exploration. DISCUSSION: Preoperative localization of primary hyperparathyroid tumors is not indicated in all patients. In some selected cases (acute hypercalcemia, reoperation, serious illness) prior neck exploration would be useful in guiding the surgeon.

Adenoma↗
PubMed1995

[Rapid peroperative assay of intact parathormone in primary hyperparathyroidism. Evaluation and comparison with the long method].

OBJECTIVES: To evaluate the efficacy of rapid peroperative assay of parathormone in patients with primary hyperparathyroidism compared with the longer standard assay. METHODS: Primary hyperthyroidism was diagnosed in 10 patients (8 males, 2 females, mean age 55 +/- 8.6 years, range 36-99) (preoperative tests: serum calcium 290 +/- 8.9 nmol/l, range 274-311; intact parathormone 137 +/- 31.3 pg/ml, range 87-250). First intention cervicotomy was performed. Blood samples were drawn at induction of anaesthesia, at palpation of the adenoma, and 15, 30 and 45 minutes after ablation. Each sample was assayed with a rapid radioimmunoassay and the longer standard laboratory methods. RESULTS: There was a good correlation between the two assay methods. In the 9 patients with a solitary adenoma, serum levels of parathormone were normalized 15 (n = 8) or 30 minutes (n = 1) after resection. CONCLUSION: Rapid radioimmunoassay is a reliable method for evaluating serum parathormone level peroperatively. Although financial implications may limit its use, this rapid assay is clearly indicated for patients in poor clinical condition undergoing first intention surgery and in those undergoing a second cervicotomy.

Adenoma↗
PubMed1992

Effects of baroceptor and cardiopulmonary reflexes on neural control of heart rate in normal man, as assessed by power spectral analysis.

This study was designed to establish the neurally-mediated effects of baroceptor and cardiopulmonary reflexes on heart rate in normal subjects. We therefore studied the effects of various interventions, able to modify the activity of arterial baroreceptors and cardiopulmonary receptors, on the power spectrum of the R-R interval in nine healthy men. To confirm the efficacy of these interventions left ventricular volume was monitored using a portable radionuclide probe. Isosorbide dinitrate (5 mgm sublingually) while sitting unloads both baroreceptors and the cardiopulmonary receptors; it decreased left ventricular end-diastolic volume (p < 0.01) and the mean R-R interval (p < 0.005), increased the power of the low-frequency (LF) component of the R-R interval (p < 0.01), decreased the power of the high-frequency (HF) component (p < 0.005) and increased the LF/HF ratio (p < 0.05). The application of cuffs around the thighs in the supine position, which unloads only cardiopulmonary receptors, decreased left ventricular end-diastolic volume (p < 0.05) but did not affect mean R-R interval, LF component, HF component and LF/HF ratio (p > or = 0.10). Leg raising, which loads only cardiopulmonary receptors, increased left ventricular end-diastolic volume (p < 0.05) and did not affect the mean R-R interval, LF component, HF component and LF/HF ratio (p > or = 0.10). In conclusion, our data suggest that, in normal man, baroreceptor unloading increased sympathetic and decreased parasympathetic neural control of heart rate; cardiopulmonary reflexes do not appear to have a direct neurally mediated effect on heart rate.

Adult↗
PubMedDate not supplied

Parallel visual and memory processes.

We studied parallel processes: visual processes with the prosaccade, the no-saccade and the antisaccade task on the one hand and memory processes with the random tap task on the other hand. The random tap task is believed to be a pure interference task for the central executive component of working memory. The number of saccadic errors was found not to be influenced by taxing the central executive, while the latency times were significantly increased both in the prosaccade and in the antisaccade task. The effect seen in the antisaccade task was expected since it is a non-automatic activity under central executive control. Because the prosaccade task is an automatic activity, an effect of central executive load was not expected. As an explanation for our findings, we postulate that the prosaccade task is brought under willed control of the central executive.

Adolescent↗