Some experiments revealed differences in event-related potentials recorded at posterior sites contralateral versus ipsilateral to the relevant visual field ('posterior lateralization') when participants were instructed to attend to a specific form or color. This posterior lateralization may be interpreted as a reflection of attentional selection. If this interpretation is correct, possible differences in the timing of attentional selection should be reflected in effects on the onset of this lateralization.
In two experiments, bilateral stimulus arrays were used. In a first experiment, participants had to respond either to the side where a square or to the side where a red element was presented. In a second experiment, they had to attend to either a square or a red element, but their response had to be based on either the color or the form of the attended element. EEG lateralization to the relevant stimulus side was corrected for exogenous effects. The difference in onset of lateralization between conditions was evaluated by using Jackknife averaging.
Both experiments showed that posterior lateralizations occurred earlier when participants had to attend to red than when they had to attend to a square. Thus, the onset of lateralization appears to reflect the timing of attentional selection, confirming the assumption that this posterior lateralization reflects attentional selection. (supported by DFG, Ve 110/7-1, 110/7-2).
Poster in der Gruppe Wahrnehmung und Aufmerksamkeit II, Mittwoch, 31. März 1999, 17:00-19:00, Foyer 2. Stock
