The prevalent view of binocular rivalry holds that it is a competition between the two eyes mediated by reciprocal inhibition among monocular neurons. This view is largely due to the nature of conventional rivalry-inducing stimuli, which are pairs of dissimilar images with coherent patterns within each eye's image. Is it the eye of origin or the coherency of patterns that determines perceptual alternations between coherent percepts in binocular rivalry? We break the coherency of conventional stimuli and replace them by complementary patchworks of intermingled rivalrous images. Can the brain unscramble the pieces of the patchwork arriving from different eyes to obtain coherent percepts? We find that pattern coherency in itself can drive perceptual alternations, and the patchworks are reassembled into coherent forms by most observers. This result is in agreement with recent neurophysiological and psychophysical evidence demonstrating that there is more to binocular rivalry than mere eye competition.

Visual development is thought to be completed at an early age. We suggest that the maturation of the visual brain is not homogeneous: functions with greater need for early availability, such as visuomotor control, mature earlier, and the development of other visual functions may extend well into childhood. We found significant improvement in children between 5 and 14 years in visual spatial integration by using a contour-detection task. The data show that long-range spatial interactions-subserving the integration of orientational information across the visual field-span a shorter spatial range in children than in adults. Performance in the task improves in a cue-specific manner with practice, which indicates the participation of fairly low-level perceptual mechanisms. We interpret our findings in terms of a protracted development of ventral visual-stream function in humans. Human visual development has been considered to be relatively fast and to give way to cognitive development after the basic visual functions are established in infancy, e.g., a very early preference for moving stimuli (1); the ability to process complex motion information at 4 months (2); color (3) and depth (4) discrimination also at around 4 months; and rapidly increasing acuity during the first year (5). However, human anatomical data indicate that, although the gross anatomical structure is constructed before birth, the maturation of neuronal circuits of the visual cortex may extend well into childhood (6, 7). More recent studies even raise the possibility of a significant increase in the number of cortical cells between birth and 6 years of age (8), implying a strikingly extended structural maturation of the human cortex, including the early visual areas (9). In light of these results, the question arises as to whether the maturation of human vision really comes to an end by the first or second year of life.Although behavioral studies of human visual development beyond the second year of age are rare, there is indication that children may encounter problems in tasks involving integration of information across the visual field for object representation: visual segmentation and form identification based on contrasts in texture (10, 11), motion (12), or color (13) and recognition of incomplete objects (14). Here, we directly test the development of visual spatial integration in a contour-detection task. We find that children (aged 5-14 years) perform poorly in the task compared with adults. Our control results clearly show that perceptual immaturity lies behind the poor performance. The results also suggest that there is immaturity at the level of long-range spatial interactions that might span a shorter spatial range in children than in adults. Experiment 1: Human Development of Spatial IntegrationTo segment the visual image and to form object boundaries in the course of perceptual organization, local orientational information extracted by selectively tuned neurons has to be integrated across the visual field. The efficiency of the integra...

We describe a region-based shape representation that might be particularly useful from a biological perspective because it promotes the localization of objects, and object parts relative to each other. The proposed medial-point representation is similar to medial-axis type representations, but it is more compact. The medial points are those points along the medial axis that are equidistant from the longest segments of the boundary, therefore they represent the largest amount of edge information. The main advantage is that the original image can be reduced to a small number of points. We also provide psychophysical correlates of the representation for shapes with increasing complexity. Using a reverse mapping technique, we find that variations of contrast sensitivity within figures are defined by the shape of the bounding contour, and the peaks in the sensitivity maps correspond to the medial points of the proposed representation.

These data are further evidence that perceptual organization impairments in schizophrenia are illness severity-related, and that schizophrenia patients as a whole are less sensitive to top-down manipulations in this type of task.