THE ROLE OF THE BLOBS IN DETERMINING THE PERCEPTION OF DRIFTING PLAIDS AND THEIR MOTION AFTEREFFECTS

Motion aftereffects (MAEs) can be induced by adaptation to a pair of d ifferently oriented drifting gratings whether the gratings are present ed simultaneously, as a coherent plaid, or in alternation. The fact th at the former MAEs were generally larger than the latter led to the su ggestion that simultaneous adaptation involved higher-level extrastria te processes not involved in the alternating effects. In the past few years evidence has accumulated that the difference is in fact due to a low-level monocular process which can be termed the 'blob-tracking me chanism'. A review is presented of the evidence on MAEs induced by sim ultaneous and alternating adaptation, the evidence for the monocularit y of the blob-tracking mechanism, the data which implicate the blob me chanism in the determination of MAE magnitude, perceived plaid drift d irection, and in perceived plaid coherence.