Optic fibers from a portion of each retina cross to the other side of the brain and form the optic chiasm. This transfer of learning was immediately abolished when the posterior 1/3 of the callosum \-laS cut. Downer found the absence of interhemispheric communication for pattern and color discriminations after part of the chiasm and corpus callosum (45).
An apparent conflict of interpretation has appeared in the reports of the relationship between the two so far. Adversarial discriminations have been used to test the independence of the two halves of a split brain during learning. In no case was there any confusion or frustration in the behavior of the subjects.
It was immediately noticed that any learning imbalance between the two halves of the brain could be related to the development of a habit for using a particular limb. Finally, observations were made in an attempt to understand the dynamics of attentional processes that.
CHAPTER II
A longitudinal incision was made in the dura to the left of the sagittal sinus and deflected toward the falx cerebri. In the case of IGR, there was a shift from preferential use of the left eye in the learning of task B. It is clear that the learning from the right eye \1aS preserved in a part of the brain,.;here it was available to the left eye when this was forced in.
In both cases, retention by the right eye remains unaffected by the new learning of the left eye. After training the left eye, the right eye was oblivious and adopted a position preference to the right. The retention of the new discrimination by the right eye was not perfect, the first set of ten trials recorded 4 errors.
Subsequently, both engrams were retained, the retention being somewhat less effective in the case of the left eye. Analyzes of the distribution of scores for binocular learning and for monocular learning of. After the criterion, there is a drift towards using the left hand, but there are almost no errors.
Hence the momentary retention of the right eye when the movements of the left hand were excluded. In the learning of the remaining tasks, IGR led to a decreasing tendency to switch from using the left hru1d. These differences in ability may reflect the diverse use of the hands by the bridge subjects.
Similar developments in the learning curve have at least been noted in monocular learning. Forced use of the hands one at a time was followed by improvement in both combinations with the right eye. Since most binocular tests involve learning, the left is used. hand, this implies that visual retention by the right.
This shift was stabilized by a period of forced use of the least preferred hand alone.
CHAPTER IV
A dual memory, consisting of two equal but opposite components of "ms held in the two hemispheres of the brain. As noted in the introduction (p. 8), the use of the forelimbs for response provides opportunities for asymmetric brain involvement part in the sensory-motor association processes. If only one eye learns, it is the one that is connected to half of the brain as well.
The speed of the s,"Tinging of attention bet'ifeen the eyes", would determine the roughness of fluctuations to be observed in the ladder. The use of the term "competition" is surpassed by the occurrence of numerous fluctuations called rivalry in human subjective awareness. There may be alternate use of one eye at a time, as in interocular rivalry, and yet the learning gains of the bm eyes may remain equal.
Most of the fibers of the latter nucleus apparently pass to the striate cortex of the posterior occipital pole of each hemisphere. Currently, it is known that colored visual effects are produced by stimulation of the human visual cortex (8). Blindness over parts of the visual field results from striate lesions in humans (75), and elements of pattern recognition processes have been observed in the cat's striate cortex (76).
It goes vertically to structures of the brainstem and which are therefore not separated by split brain surgery. Ph~siol0 of the Retina and Visual Pathv-laY (1960, The Hilliam and Wilkins Co., Baltimore. A peanut butter given on each side was selected and the distribution of the stimuli on the screens varied in the usual " ,jet.
I is projected separately to the two eyes using the polarized filtering technique. Each circle of the pair was projected onto one of the response screens in the same apparatus as the VlaS used for studies of dual learning of conflicting tasks. This result is in contrast to the studies that have demonstrated the separation of the two visual learning systems at the operation.
A monocular test of 20 trials with the left eye contained 15 correct moves; 13 moves ;'1 are made by the right hand, including 4 of the 5 mistakes. For this second task the tendency to use the contralateral limb Nith vision of one eye at a time shoi"ffi be t'leaker.
