Lorazepam and diazepam differently impair divided attention.

Effects of ethanol (EtOH, 0.65 + 0.35 g.kg-1), diazepam (DZ, 15 and 30 mg), lorazepam (LZ, 2 mg) on divided attention were measured in two placebo-controlled crossover studies with healthy young subjects. The test comprised four parallel computer screens with a ball moving along a circular obstacle course on each screen at different rates. When the ball entered an obstacle on any screen, the subject had to press the respective button. The obstacles varied in numbers and shapes, and randomly changed their location every 10 s. Concomitant aural stimuli were responded to by pushing the foot pedals. The primary visual variables were the absolute and percent numbers of correct responses on each screen. Concentrated attention was measured with a symbol digit substitution (SDST) and digit copying (DDCT) tests, for 3 min each. In Study I, with 12 subjects, the tests (4 min) were made before the treatment (placebo, EtOH, DZ) and 1, 3, and 6 h after intake. EtOH impaired attention on the lateral but not on medial screens, with and without aural stimuli, the "special" obstacles of deviating shape being the most sensitive targets to EtOH effects. DZ 15 mg did not modify divided attention whereas it impaired SDST performance and was subjectively slightly more potent than EtOH on visual analog scales. DZ 30 mg impaired attention on the lateral screens, with and without aural stimuli, but without preference to "special" obstacles. It also reduced responses to aural stimuli, strongly impaired SDST and DDCT, and caused subjective sedation. In Study II, with 9 subjects, the test run without aural stimuli was easier but lasted for 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)