Attentional modulation of motion-in-depth processing

I used a novel effect of adaptation to a moving stimulus to investigate the role of attention in the processing of motion-in-depth (MID). Following adaptation to expansion, the time required to detect an expanding target in the same location as the adaptation target was significantly longer than following viewing of a constant-sized target. Conversely, following adaptation to contraction, detection times (DTs) for an expanding target were significantly shorter than for a constant-sized adaptation target. Changes in DTs following adaptation to contraction were substantially larger than those following adaptation to expansion. Attentional modulation of MID processing was examined by adding an alphanumeric discrimination task that distracted the observer's attention away from the location of the adaptation target. I compared the magnitude of DT effects while (a) observers passively fixated the alphanumeric sequence (single task condition) and (b) observers performed the discrimination task (dual task condition). DT effects were significantly smaller in the dual task condition than in the single task condition indicating that MID processing is modulated by attention.