Effects of flunitrazepam on responses to lateralized visual stimuli: evidence for cerebral asymmetry of execution of manual movements to targets in contralateral and ipsilateral visual space.
In order to examine the effects of benzodiazepines on response execution by the left and right hemisphere, flunitrazepam (1 mg) or placebo was administered to healthy, right handed volunteers in two separate experiments. In experiment 1, drug was administered daily during a treatment period of 8 days, and subjects were instructed to fixate vision centrally and to execute laterally directed manual responses corresponding to the position of visual stimuli presented in either the right or left hemifield. Experiment 2 was performed with a single dose and cross-over design, and subjects responded to the laterally presented visual stimuli by key press of a centrally positioned response device, i. e. neither detection of position of the stimulus in space nor response selection was required before initiation of the response. In experiment 1, intake of flunitrazepam generally increased reaction time more during response execution by the left as compared to the right hemisphere, and the most pronounced effect was observed on responses with the right hand, directed across the body axis, to visual stimuli presented in the left visual field. In contrast to these observations, in experiment 2, flunitrazepam impaired responses with the right and left hand practically to the same extent. Together, the results indicate that benzodiazepines may affect manual responses executed by left and right hemisphere differently, and that this asymmetry may be related to a stimulus-response compatibility effect in tasks that require response selection.
National Institute of Forensic Toxicology, Oslo, Norway.
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Ingum
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Bjørklund
D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004361:Drug Tolerance; D005445:Flunitrazepam / Q000494:pharmacology*; D007839:Functional Laterality / Q000187:drug effects*; D006801:Humans; D008297:Male; D009068:Movement / Q000187:drug effects*; D011930:Reaction Time / Q000187:drug effects; D013028:Space Perception / Q000187:drug effects*; D014785:Vision, Ocular / Q000187:drug effects*
D005445:Flunitrazepam