Biomedical subjects

C Possamaï

Publications and source records attributed to C Possamaï.

3 recordsLinked to original sources

PubMed2001

N-methyl-D-aspartate receptors and information processing: human choice reaction time under a subanaesthetic dose of ketamine.

Ketamine is an N-methyl-D-aspartate antagonist that induces cognitive dysfunctions. The purpose of the present study was to investigate the effects of a subanesthetic dose of ketamine on human information processing, using the additive factor method. During perfusion of a subanesthetic dose of ketamine (0.5 mg/kg over 60 min) or a placebo (randomized double-blind, cross-over design), eight adults (aged 22-33, mean=27) performed a two-choice visual reaction time (RT) task. Signal intensity, stimulus-response mapping, and foreperiod duration were manipulated. The effects of these three variables were found to be additive on RT, indicating that three independent stages - namely, stimulus preprocessing, response selection and motor selection- were manipulated. Ketamine altered RT performance in a specific way: it interacted with foreperiod duration but its effect was additive with those of signal intensity and stimulus-response mapping. These results show that ketamine specifically affects the stage of motor adjustment, which suggests that the glutamatergic system plays an important role in motor processes.

Acoustic Stimulation↗

PubMed2000

The additive factor method in rat information processing.

Sternberg introduced the additive factor method as a tool for discovering and studying in choice reaction time situations in human subjects. Underlying the method is the notion that if information processing consists of successive stages, then different factors affecting different stages must have additive effects on reaction-time measurements. The additive factor method has been extensively used in humans but few attempts have been made to examine whether or not additive reaction time patterns were obtainable in rats. In the present work, the subjects (13 Long-Evans rats) had to press down a lever and to respond to a visual (right or left) stimulus by releasing the lever and introducing the head into a lateral (right or left) operandum. The present findings show an additive pattern of effects of signal luminance and foreperiod duration on the mean reaction time which suggests that we have successfully manipulated two stages of rat information processing - the preprocessing stage and the motor adjustment stage, respectively. Accordingly, the present study sets the basis for the basis for investigating the effects of invasive manipulations (pharmacological and/or lesional) on information processing stages.

Journal Article↗

PubMedDate not supplied

Levodopa-induced drowsiness in healthy volunteers: results of a choice reaction time test combined with a subjective evaluation of sedation.

The aim of the present study was to assess levodopa (L-Dopa)-induced drowsiness in healthy volunteers using two parameters: choice reaction time and a subjective rating of sedation. Sixteen subjects participated in a randomized, double-blinded, crossover study. A single dose of 200 mg L-Dopa or placebo was administered at 9:00 AM. To limit peripheral side effects connected with L-Dopa, subjects were treated with 20 mg domperidone three times daily. Subjective rating of sedation consisted of visual analogue scale. Reaction time was measured by means of responses to two light-emitting diodes. The illumination of one of these diodes constituted the imperative signal. Manual responses were performed on two buttons located under the right and left index fingers. Results demonstrated a positive correlation between sedation level and reaction time (r = 0.70, p = 0.0026). Adverse events of L-Dopa were nausea (four cases) and excitation (one case). Subjects who did not develop adverse events were faster under L-Dopa than under placebo (p = 0.02), whereas subjects who had nausea or excitation were slower. A single dose of L-Dopa either deteriorated or improved choice reaction time in healthy volunteers according to whether it was sedative and whether it generated disruptive adverse events.

Adult↗