A new pharmacological tool to investigate integration processes

Recent work is presented to suggest that lorazepam (a benzodiazepine), enha ncing 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 letter s, suggested that lorazepam enhances the processing of line-ends. These res ults are generalized to simpler stimuli. In Experiment 1, subjects had to d etect the presence of corners in fragmented squares. In Experiment 2, they had to discriminate between continuous and discontinuous stimuli. In both e xperiments, elements were either collinear or parallel. The results suggest ed that lorazepam improved detection of discontinuities and impaired integr ation for collinear elements. These results sustain the hypothesis that lor azepam enhances responses to line-ends. They are related to studies suggest ing that line-ends are coded by end-stopped cells and that GABA is involved in the generation of end-stopped cell responses.