Enhanced GABA_A inhibition enhances synchrony coding in human perception

Abstract

The benzodiazepine, lorazepam enhances the efficiency of local, inhibitory GABA_A synapses in the cortex, which stabilize postsynaptic, excitatory activity by synchronizing their own discharges at around 40 Hz. Treatment with lorazepam has also been shown to adversely influence detection performance in perceptual tasks, suggesting a role for GABA_A-mediated synchronization during visuo-perceptual organization. Consistent with these findings we report that reaction times to target stimuli were slower following lorazepam treatment. However, when targets followed presentation of a synchronized prime, presented within a flickering 40-Hz display matrix, the effects of priming were amplified relative to baseline and control conditions. We conclude that enhanced GABA_A-induced inhibition enhances stimulus-evoked synchronization with differential effects upon mechanisms of perceptual segmentation and grouping.