Effects of stimulus location on automatic detection of changes in motion direction in the human brain.

We extended the results of a previous report by further exploring the underlying mechanisms of an electrophysiological index of attention-free memory-based detection mechanism to motion-direction changes in the human visual system. By means of presenting bilateral, right- and left-hemifield stimulation in separate conditions, we tried to assess whether the location of the stimuli within the peripheral visual field affected the processing of motion-direction deviations, and to identify brain regions involved in the detection of unattended infrequent changes of motion direction using low-resolution brain electromagnetic tomography (LORETA). Results indicated that the ERP component related to visual change was not affected by stimulus location, and that bilateral temporal and medial regions were activated during this deviance-related response regardless of the hemifield stimulated. The bilateral activation foci observed in this study suggest that brain generators of this deviance-related component could be located at the vicinity of motion processing areas.