BENZODIAZEPINE EFFECTS ON FLICKER SENSITIVITY - ROLE OF STIMULUS FREQUENCY AND SIZE

1. Benzodiazepines (BZDs) impair sensitivity to temporally modulated v isual stimuli (flicker). Critical flicker-fusion frequency (CFF) is co mmonly used as a measure of this effect, but it only measures sensitiv ity to a narrow range of frequencies, usually above 25 Hz. Are other f requencies more sensitive to the effects of BZDs? 2. Flicker sensitivi ty at 1, 2, 4, 8, 16, and 32 Hz was measured for 1-degrees, and 5-degr ees stimuli before and 50 to 100 minutes after triazolam (0.25 mg), lo razepam (1.0 mg) and placebo. Drug effects on CFF were also measured. 3. Both BZDs significantly impaired overall flicker sensitivity. Triaz olam produced 50% more impairment than lorazepam. CFF was significantl y impaired by triazolam. BZD effects did not vary with stimulus size. 4. Significantly greater BZD-induced impairment of flicker sensitivity occurred at 16 Hz than at 1, 2, 4, or 32 Hz. 5. The magnitude of BZD effects on flicker sensitivity vary with the temporal frequency of the stimulus. BZD effects are greatest for 8-16 Hz stimuli.