Abstract
The effect of attention on detection/discrimination of basic stimulus features such as motion and disparity can be demonstrated using a dual RSVP paradigm. Participants are asked to await the onset of a cue embedded in a RSVP stream before detecting the presence of a stimulus in a second RSVP. We have previously shown that normal observers are impaired in detecting salient stimuli such as first order motion or detecting a large change in disparity of a surface if it occurs within a 300ms time interval after the cue onset (VSS 2004). The recovery functions for detection of both features (motion & disparity) following the cue onset and their relationship with the frequency of distractor events are similar for both features.
We have now demonstrated that the cue, embedded in an RSVP stream, can be either visual (a unique red fixation colour) or auditory (a specific tone). We have proposed that the impairment is due to the active suppression of the distractor events by top-down mechanisms. The cue simply acts as a temporal marker, signalling the release of suppression and therefore, it is independent of its modality. The time-course of the recovery, therefore, would reflect the gating of information to higher-order stimulus evaluation (or controlled stimulus processing) and not the interference of cue processing within a modality. The findings have also been supported by our recent electrophysiological studies (Niedeggen et al. J. Cogn. Neuro, 2004).
Volkswagen Foundation (grant 2277)