Attention to features of separate objects: an ERP study of target-shooters and control participants.

In a visual discrimination task stimuli consisted of a color circle and a grating pattern, i.e. target features were distributed between two objects. The relation (hierarchical vs. parallel) between the attentional processing of the task-related features (color and spatial frequency) was investigated by using the methods of event-related potentials (ERPs). Participants with considerable practice in visual attention (target shooters; n = 13) were compared to control subjects (n = 11). Attention-related ERP components, i.e. selection (anterior) positivity (SP), selection negativity (SN), N2 (N2b), furthermore the late positivity (P3b) emerged only if the circle had relevant color. These results suggest preponderance of color processing. Target shooters were faster and more accurate than the control group. Attention-related components (SP, N2b) and the late positivity (P3b) were larger in shooters, but the relations among the attention-related components were the same in two groups, showing similar progression of the target selection process.