Abstract
This study examined the effects of preceding stimulus types on the attention-related negative waves (Nd waves) of event-related brain potential (ERP), especially on the amplitudinal decreases caused by dividing one's attention to multiple sound sources. Pure tones of 100ms in duration were presented repeatedly to either the right or left ear at random intervals (either 200ms or 600ms in stimulus onset asynchrony [SOA]). Twelve human subjects performed target detection tasks in a designated ear (selective attention task) and in both ears (divided attention task). The Nd wave attenuation caused by dividing one's attention was compared between differing preceding stimulus direction (same or oposite) and differing preceding SOA (either 200ms or 600ms). In this study, no noticeable differences between preceding stimulus types were observed, suggesting that neither increases in the frequency of processing nor spatial shifts in attention are significant causal factors in Nd attenuation. Therefore, the division of one's attention among spatial locations is necessary.
