A new pharmacological tool to investigate integration processes

Recent work is presented to suggest that lorazepam (a benzodiazepine), enhancing the inhibitory effect of GABAA, might be a useful tool to investigate visuo-perceptual integration processes and to link experimental psychology and electrophysiology. Previous results, obtained with drawings and letters, suggested that lorazepam enhances the processing of line-ends. These results are generalized to simpler stimuli. In Experiment 1, subjects had to detect the presence of corners in fragmented squares. In Experiment 2, they had to discriminate between continuous and discontinuous stimuli. In both experiments, elements were either collinear or parallel. The results suggested that lorazepam improved detection of discontinuities and impaired integration for collinear elements. These results sustain the hypothesis that lorazepam enhances responses to line-ends. They are related to studies suggesting that line-ends are coded by end-stopped cells and that GABA is involved in the generation of end-stopped cell responses.