The automatic processing of visual information at different visual acuity levels: An ERP study

•We studied the correlation between ERPs and visual information capacity.•Supra-threshold and threshold stimuli could elicit the same vMMN.•P3a reflects the differences in the processing of supra-threshold and threshold stimuli.•Brain is able to detect visible optotypes under a non-attentional condition in adults.•We provide evidences for the ERP-based acuity testing.

This study investigated the subjective visual acuity by recording ERPs elicited by task-irrelevant visual changes. Optotypes stimuli were presented in the center of the visual field at three threshold levels (supra-threshold, threshold and sub-threshold) while participants were listening to stories. The results showed that neither vMMN nor P3a component was elicited by optotypes stimuli on the sub-threshold condition, whereas, vMMN was elicited under supra-threshold and threshold conditions, with no significant differences between those vMMN amplitudes of two conditions. The P3a amplitude was larger for supra-threshold condition than that for threshold condition. These data demonstrated that the emergence of vMMN could only reflect the automatic detection of orientation-changes in the supra-threshold and threshold conditions compared to the sub-threshold condition, whereas the P3a amplitude could reflect the difference in processing of supra-threshold and threshold stimuli.