MIB Transition for Real and After-image Seiichiro Naito, Ryo Shohara, & Makoto Katsumura Human and Information Science, Tokai University, JAPAN P20-61 Introduction: Time transition of Motion Induced Blindness (MIB) was investigated using the dedicated stimulus configuration. The onset and offset time delays of MIB after the inducing figures’ onset and offset moments were estimated. The MIB for after image test figures was also investigated in a similar way. The after image was created in such a way that at the MIB onset moment the test figure was changed to the background color. Methods: Twelve 2.5 degree diameter colored disks were circularly arranged at 12.5 degree periphery. They were test stimuli. At the two symmetrical positions, the black ring shaped inducers were presented. They expanded from the disk border to 5.5 degree diameter in 167ms and vanished. Then the inducers shifted its position in anti-clock wise direction to the neighboring disk. The procedure repeated. Results: The short onset time delay not more than 167ms was observed. MIB effects lasted more than 333ms even after the inducers vanished. For after images, the similar onset delay was observed and MIB could last more than 900ms after the inducer vanished. Conclusions: The onset and offset time delays of MIB were confirmed in general. The delays varied quantitatively depending on the stimuli configurations and time sequences. Visit on-line demo : Stimulus At 12.5 degree periphery from the center fixation point, 12 differently colored with black rim 2.5 diameter disks were arranged similarly to a clock face. They were the test figures. At the two opposite positions, the black ring shaped inducers were presented. They expanded from the disk border to 5.5 degree diameter size in 167ms and vanished. Then the inducers shifted its position in anti-clock wise direction to the neighboring disk. The sequence repeated indefinitely. The inducers rotated the whole circle in 2 seconds. Percept At the inducer, the test circle was visible. Therefore at least 167ms or less onset time delay was confirmed. The following 2 or 3 colored disks were invisible, instead the subjects perceived the white background. The 2 blank disks meant that MIB was sustained for 333ms after the inducers vanished. Colored background and white test figure The white test disks on the colored background stimulus were more effective condition for MIB. There was no after- image while MIB. Stimulus was same as the real image condition except that the test disk at the inducer position and the following 2 disks turned to be white. The right panel is the stimulus for detailed observation of MIB sequence. The upper and lower halves alternated every 2 seconds. The vivid pink after-image for the cyan disk at 8 degree of 6.5 degree diameter was observed. The back rings were the inducers. They appeared with 700ms delay after the alternation. The inducers expanded from the border of 6.5 diameter test disk (after-image) to 16.3 degree diameter in 390ms. At the onset of the inducer the afterimage disappeared and continued to be invisible even after the offset of the inducer for 910ms until next alternation. The after-image MIB gave the idiosyncratic long offset time delay. The background turned to be white. The aftereffect tinted the background complementary color. The white disk in turn was tinted the adaptation color again by simultaneous color contrast. Percept was almost similar to the after-image condition. The substantially long offset time delay of 910ms or more was idiosyncratic for the after-image color contrast MIB as well. Possible account of MIB The onset time delay suggested a possible account of MIB: The feedback to V1 from extrastriates such as MT is necessary for conscious visual experience. The trasillient rapidly moving inducer was the dominant feedback to V1 than that of fully adapted static test figures. Thus the test figures disappeared after short onset time delay that was required for the inducer to loop back. The offset time delay remained untenable. The substantially long offset time delay of 900ms was idiosyncratic for A- and ACC-MIB. MIB for real image MIB for after-image (A-MIB) MIB for simultaneous color contrast induced by after-image (ACC-MIB)