Abstract
Behavioral studies using reports of target items after a cue from a rapidly presented stream of potential targets (i.e., RSVP, Weichselgartner & Sperling, 1987) and studies measuring event related potentials (ERP, Hillyard et al, 1998) both indicate a time course of attentional gating of about 100 ms. In the present study, the temporal dynamics of attentional shifts to a peripheral cued location were examined in a contrast discrimination task. In particular we assess the earliest time from cue onset in which information can be used at the attended location. We estimate this use of information by the spatiotemporal analog of the classification image technique (classification movie, Xing and Ahumada, 2002). Methods: Two observers had to detect the presence of a Gaussian (stdev= 8.2 min) contrast increment (yes/no task; 50% probability of target presence) embedded in a temporal sequence of independent frames of spatially uncorrelated noise (frame rate= 40 f/s) displayed for 450 ms. The target was randomly located in one of eight locations equidistant from fixation at an eccentricity of 4.6 deg. A 100% valid simultaneous cue indicated the probable location of the target. The noise fields at the cued location on the signal absent trials (false alarms and correct rejections) were used to estimate the spatial perceptual filters of the observer at the cued location at different temporal intervals from cue onset (classification movies). Results: Observers showed significant estimated perceptual filters at the cued location within 25–50 ms. Conclusions: Our results suggest the use of information at an attended location begins 25 to 50 ms after a peripheral cue to shift attention, earlier than estimates from previous studies.