Dynamic random-dot stereograms and correlograms were used to elicit visually evoked brain potentials from human infants, and these potentials were compared with potentials evoked by classical checkerboard pattern reversal. The results indicate that infants begin to produce stereoscopically evoked potentials at the age of 10 to 19 weeks, several weeks after showing classical checkerboard-evoked potentials, and suggest that the onset of cortical binocularity precedes stereopsis.

No abstract

The combination of three technological innovations permits the fast and objective determination of stereopsis in nonverbal subjects: (i) It is shown that dynamic random-dot correlograms (RDC) are as effective as dynamic random-dot stereograms (RDS) in eliciting large evoked potentials (EP), and that the generation of RDC is simpler than that of RDS. (ii) The presentation of BUDC in the form of red-green anaglyphs is insensitive to subjects' head tilt, because alternation of correlation (binocular fusion) with uncorrelation (binocular rivalry) does not depend on the direction of binocular disparity, whereas perception of depth in RDS does. (iii) Projection TV techniques, using backprojected large screens viewed from near distances, permit noncooperative subjects (e.g., human infants or monkeys) to be surrounded with the stimulus, so they cannot look away.Dynamic random-dot stereograms (RDS), portraying areas pulsating in depth, and dynamic random-dot correlograms (RDC), alternating between binocularly identical and uncorrelated dynamic noise, have proved to be useful stimuli in the study of human stereopsis (1-3). Because these "cyclopean" stimuli lack monocular cues, and it has been shown that cortical neurons of the monkey can respond to binocular disparity changes (4, 5), random-dot stimuli are obvious candidates for probing visually evoked cortical potentials (EP) measured on the human scalp. Several investigators (6, 7) have used static RDS. However, in EP studies at least two static RDS must be alternated, which usually produce unwanted monocular cues, such as variations in local density. Recently, however, Lehmann and Julesz (8) succeeded in recording EP to dynamic RDS in which all monocular cues were absent. Indeed when dynamic noise arrays of high spatial resolution are presented at fast rates (60 arrays per sec or faster), any local density difference is averaged out for the order of magnitude slower alternation rates.We report the development of a robust technique that permits the quick determination of stereopsis by measuring large EP to dynamic RDC. With one eye closed (or if the left and right images are vertically shifted outside Panum's fusional area) only a "snowstorm" can be seen. However, when binocularly viewed (and in registration within Panum's fusional area) the correlated noise is binocularly fused and yields a flat surface in depth that alternates with a "woolly" depth percept as the binocularly correlated noise is switched to uncorrelated noise (9). We report that this perceptual pulsation between binocular fusion and rivalry elicits large EP (in excess of 10OiV) on the human scalp for subjects with functional stereopsis.We obtained similarly shaped large EP for several dozen subjects with normal stereopsis. From four subjects we recorded EP over a period of several months and their individual responses showed almost no variation. Because the closing of one eye, or the introduction of vertical disparity (or using time delay in excess of a TV frame duration) eliminated the EP res...

Since a change of stimulus is required to effect a visual response, and since saccadic eye movements change the locus of the retinal image, the hypothesis was developed that there should be a brain response following saccadic eye movement.- The hypothesis was tested experimentally by averaging the activities following successive saccadic eye movements. A response was found whose characteristics were dependent on illuminance of the stimulus.

The primate visual cortex, including that of man, receives separate input from each eye and these interact in binocular cortical neurones. This organization is known to be vulnerable to disruption in early life. To understand the development of human visual cortex, and to detect and assess disorders of binocular function at the earliest possible age, a robust method is needed for detecting binocular interactions in the infant's visual system. We have done this by recording cortical visual evoked responses (VERs) to the onset and offset of binocular correlation in a large-screen dynamic random dot display. We report here that, in general, the human infant has a functional binocular visual cortex by 3 months of age, with some individuals showing cortical binocularity at an earlier age.