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Biomedical subjects

R Bjørklund

Publications and source records attributed to R Bjørklund.

10 recordsLinked to original sources
PubMed2002

Early psychomotor slowing predicts the development of HIV dementia and autopsy-verified HIV encephalitis.

OBJECTIVES- To ask if slowed motor speed predicts later human immunodeficiency virus (HIV) dementia and HIV encephalitis. METHODS- In 100 deceased acquired immunodeficiency syndrome (AIDS) patients prior results from repeated testing of the movement reaction time test were correlated with later clinical signs of HIV dementia and with neuropathological signs of HIV encephalitis. Autopsy was performed in 72 patients. RESULTS- Movement reaction time 1-2 years prior to death, or at the time of clinical AIDS diagnosis predicted both development of HIV dementia (P<0.05) and HIV encephalitis at autopsy (P<0.01). CONCLUSION- Testing for early psychomotor slowing may be used to identify patients at risk of HIV dementia and HIV encephalitis.

AIDS Dementia Complex↗
PubMed1994

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.

Adult↗
PubMed1994

Development of acute tolerance after oral doses of diazepam and flunitrazepam.

Flunitrazepam (1 and 2 mg), diazepam (10 and 20 mg) or placebo was administered to healthy, male volunteers, and the time course of psychomotor impairment, as indicated by simple and complex choice reaction time and movement time, was studied during a period of 6 h after drug intake. To examine whether acute tolerance developed, the observed performance during decreasing drug plasma concentration was compared to the predicted performance based on kinetic-dynamic modelling of the observed performance during the first 1.5 h after intake when the drug plasma concentrations were increasing or at peak level. Placebo corrections of the test scores were accomplished to adjust for diurnal variation and the possible influence of learning during the test day. After the flunitrazepam treatments, the predictions overestimated the actual performance significantly with respect to simple and choice reaction time at the 6-h session after intake. After the diazepam treatments, however, no significant deviation was detected between predicted and observed performance. The results indicate that acute tolerance develops with respect to impairment of attention demanding performance after medium to large doses of flunitrazepam, and that tolerance is expressed after approximately 4-6 h following intake.

Adult↗
PubMed1993

Total reaction time: a new approach in early HIV encephalopathy?

In an attempt to develop better methods for diagnosis, screening and serial assessment of HIV-1-associated cognitive/motor complex, we have added a motor component to tests of reaction time, defining the new parameter as total reaction time. Thirty-four non-drug-using, HIV-positive men underwent four different tests of total reaction time. All four tests reached a level of statistical significance, both for a group of patients with early disease and for a group of patients with symptoms, compared with a control group. Total reaction time had a better discriminatory ability than standard reaction time, particularly for patients with early disease. It is suggested that neuropsychological studies of HIV-1-associated cognitive/motor complex should include tests of total reaction time.

AIDS Dementia Complex↗
PubMed1992

Relationship between drug plasma concentrations and psychomotor performance after single doses of ethanol and benzodiazepines.

In a placebo controlled, crossover study psychomotor effects of single doses of diazepam, 10 and 20 mg, flunitrazepam, 1 and 2 mg, as well as 0.9 g ethanol/kg body weight were investigated over a time period of 6 h in 12 healthy men. Blood samples were collected simultaneously with the test sessions to determine drug concentrations in plasma or blood. The ethanol dose caused the least performance impairment, followed by 10 mg diazepam. The most pronounced impairment was caused by 2 mg flunitrazepam, whereas 20 mg diazepam and 1 mg flunitrazepam caused intermediate impairment and were approximately equipotent on group level. Considerable interindividual differences with respect to maximal impairment following a particular drug treatment were observed, with poor correlation between individual maximal impairments and individual peak plasma concentrations of the drug. The maximal impairment in simple reaction time following the flunitrazepam treatments occurred earlier relative to the peak plasma concentration of the drug as compared to the diazepam treatments. This may indicate that acute tolerance develops differently for the two drugs.

Adult↗
PubMed1989

Thyrotropin-releasing hormone antagonism of ethanol inebriation.

The effect of ethanol [1 g/kg per orally (p.o.) during 1 hr] after thyrotropin-releasing hormone (TRH) pretreatment (five doses of 20 mg p.o. during 30 hr preceding ethanol intake) was studied in a placebo-controlled, double-blind design in 11 healthy subjects. Computerized reaction tests measuring errors and reaction time, as well as clinical testing and a self evaluation (modified Osgood test) were performed before, 75, 150, and 225 min after ethanol intake. TRH treatment did not influence blood ethanol concentrations. The effect of ethanol to produce errors was substantially reduced in all three reaction tests after TRH treatment compared to placebo treatment. The reaction times were slightly increased in simple and four choice reaction tests and up to 20% increased in a complex test in the TRH-ethanol situation compared to the placebo-ethanol situation. The effects caused by ethanol were also significantly reduced in three clinical tests and in two subjective tests of inebriation by TRH treatment compared to placebo treatment. In conclusion the study demonstrated that several acute effects of ethanol intake in humans were reduced by TRH pretreatment which did not interfere with the blood ethanol concentration versus time curve.

Adult↗