Abstract
It is well known that adaptation to high-contrast stimuli elevates the detection threshold for subsequently presented stimuli by about ten times (e.g., Blakemore & Campbell, 1969). Here, we demonstrate that adaptation to dynamic stimuli causes blindness for sustained stimuli in the peripheral visual field (5.9 deg eccentricity). After adaptation to a drifting grating (8 Hz), static gratings often become invisible even at 100% contrast when presented within a gradual temporal window, and the contrast thresholds (∼3% before adaptation) become immeasurable. This did not occur for test stimuli with high temporal-frequency components such as drifting gratings, or static gratings presented within a rectangular temporal window. The blindness effect was still evident even when the adapting and test stimuli were presented to different eyes, and was rather enhanced when both were presented to the same eye (the uniform background to the other eye). These seem to imply involvement of inter-ocular suppression in addition to simple sensory gain control. Importantly, the static grating, which was invisible after adaptation, became clearly visible again when it was accompanied by a transient presentation of a surrounding annulus. This indicates that early neural units respond to the stimulus even if it is not consciously perceived. We interpret these results as a new class of visual rivalry that occurs between the uniform field and the local pattern in the peripheral visual field, wherein the form information cannot reach awareness if transient signals are completely lost by adaptation. We will discuss the underlying mechanisms in relation to those of the other phenomena, including binocular rivalry, Troxler effect, motion-induced blindness, and the edge-adaptation effect (Shimojo & Kamitani, 2001, VSS).