Enhanced GABAA inhibition enhances synchrony coding in human perception Running Head: GABAA inhibition and synchrony coding

The benzodiazepine, lorazepam enhances the efficiency of local, inhibitory GABAA (-aminobutyric acid) 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 GABAA-mediated synchronization during visuo-perceptual organization. Consistent with these findings we report that reaction times (RTs) 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 baseline and control conditions. We conclude that, while enhanced GABAA-induced inhibition enhances stimulus-evoked synchronization with differential effects upon mechanisms of perceptual segmentation and grouping.