Neural correlates of pre-attentive and attentive processing of visual changes.

To identify electrophysiological correlates of pre-attentive and attentive processing of visual changes, we compared event-related brain potentials in response to color changes at attended and unattended spatial locations using a visual S1-S2 matching task. The results showed that compared to no change, change stimuli elicited occipito-temporal positivity at around 100-160 ms (change-related positivity) and subsequent central negativity at around 220-300 ms (N270). Change-related positivity was observed in response to changes at both attended and unattended locations, while N270 was observed only when attention was directed to the location of the changes. These results suggest that change-related positivity reflects the pre-attentive processing of visual changes and N270 reflects the attentive processing of visual changes in the human brain.