Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The present set of experiments used adaptation procedures to explore binocularity in individuals with abnormal binocular vision. The first series of experiments examined interocular transfer because this measure has been used previously to test for the presence of binocular neurons (Movshon, Chambers and Blakemore, 1972). Experiment I examined the test-retest reliability of this measure. Interocular transfer was found to be reliable. The results of Experiments II-IV clearly show that individuals with anomalous early visual history (A.E.H.) are capable of interocular transfer of a magnitude associated with normals.;Experiments III and IV also addressed the organization of binocular channels in individuals with varying levels of stereopsis. The results from Experiment III supported the presence of two binocular channels in Normal subjects whereas the A.E.H. group showed evidence for only one binocular channel. This pattern of results for the A.E.H. group was not as clear in Experiment IV, but the Normal group displayed data consistent with two binocular channels.;A different paradigm, alternating monocular adaptation, was used in Experiments V and VI in a further attempt to evaluate the number of binocular channels present. The results from Experiment V were quite clear. Individuals without stereopsis showed evidence of only one binocular channel and the Normal group portrayed the pattern of results indicative of two binocular channels. The results From Experiment VI were equivocal regarding both the Normal and A.E.H. group.;Experiment VII revealed that all subjects of the A.E.H. group were capable of obtaining a level of binocular summation associated with probability summation. The Normals showed summation levels indicative of neural summation. In Experiment VIII, the data show that if the stimuli presented to each eye are not spatially matched, then summation decreases. However, this was true only for the Normal group. The Stereoblind group maintained a level of probability summation throughout the stimulus phase shifts. The final experiment used subthreshold summation and adaptation procedures to affect the purely binocular channel in order to reduce summation. Summation decreases after adaptation of this channel, but remains unchanged if this channel is not adapted. The results for the Stereoblind group were the same as the Normal group, suggesting that Stereoblinds maintain a binocular channel affected by simultaneous stimulation.;These results clearly show that individuals with anomalous early visual histories show evidence for binocular channels previously thought to be absent.



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