Abstract
In this study we examine the integration of motion signals from random dots moving within a circular patch (3.3° in diameter) that was presented for 5120 ms and moved along either a smooth or discontinuous trajectory. The dots within the patch moved either toward or away from the central fixation point and the patch itself moved along a circular path 6.1° from fixation at 70.3 deg/sec in one condition or jumped to random locations around the 6.1° radius circle each 160 msec in the other. The two paths (smooth vs. random) and the two directions of dot motion (inward or outward) were randomly interleaved during each block and the dot motions were presented at several different coherence levels. Subjects' task was to report the direction of the dot motion (inward versus outward). When the circular patch moved smoothly, the coherence threshold was 24% (for 75% correct). However, when the region jumped randomly, the coherence threshold was dramatically higher, 51%, even though the motion was present for the same duration in both cases. Motion integration across discontiguous locations appears to be less efficient than tegration along a continuous path.