License to See: for One Eye Only?

Stefan Treue be adequately processed. A well-studied example of such a selection process is selective attention, the ability Cognitive Neuroscience Laboratory Sektion fü r Visuelle Sensomotorik to allocate processing resources in a nonhomogeneous manner, enabling the detailed analysis of stimuli of inter-Dept. of Neurology University of Tü bingen est while at the same time not wasting neural processing resources on uninteresting information. Selection pro-72076 Tü bingen Federal Republic of Germany cesses such as binocular rivalry or attention cannot work without segmentation. Only if we can segment the visual input can we effectively discriminate and separate significant from insignificant information. As we shall see While crossing our eyes results in the disorienting per-later on, some of these selection processes appear to cept of double vision, it also offers a glimpse into a host work on the level of surfaces and objects, suggesting of issues of visual information processing. The misalign-an important role for these tokens in visual perception. ment of the two eyes results in incompatible images This list amply demonstrates the possibilities offered by projected onto the two retinae. While the slight differ-a better understanding of binocular rivalry to almost all ences between the left and the right image caused by of current visual (and by extension other sensory) sys-the different positions from which the eyes view the tem neuroscience. It is thus no surprise that the phenom-world (called binocular disparities) are used to recover enon has attracted a lot of psychophysical interest. A the distance or 3-D shape of objects in a process called number of investigations have established the precise binocular fusion, the two images when squinting are too conditions that will cause rivalry but, interestingly, have different to be fused and now compete for access to resulted in notably different predictions about where in our conscious perception. Rather than perceiving two the visual pathway it is produced. images transparently overlayed on top of each other, Some experiments suggest that binocular rivalry oc-we see a mosaic of objects and features patched to-curs when the signal from the two eyes are still segre-gether from the images on the retinae, something aptly gated, i.e., before or at the level of primary visual cortex called binocular rivalry. This patchwork is in constant (V1, the area where visual information from the eyes first change as the balance of power between the two images reaches cortex). For example, Fox and Check (1968) is …