Charles L. Sheridan

Monocular acquisition and interocular transfer in albino rats with unilateral striate ablations

Monocular acquisition and interocular transfer of a horizontal-vertical discrimination were measured in 18 albino rats with unilateral lesions of the striate cortex and in 9 unoperated Ss. Ss trained with the eye contralateral to the lesion failed to learn the discrimination unless it had previously been acquired via the ipsilateral eye. Ss trained via the ipsilateral eye learned quickly if ipsilateral-eye training came first, but performed erratically if ipsilateral training followed contralateral training. Interocular transfer occurred in unoperated Ss, but it was incomplete.

Differences in the effectiveness of optic uncrossed fiber systems in albino and hooded rats

Pattern discrimination performances were evaluated in albino and hooded rats surgically limited to uncrossed optic fiber systems. These pathways proved far less effective in albino than in hooded rats, thus providing a partial explanation of the marked differences in interocular transfer exhibited by the two strains.

Interocular transfer in the rat: The role of the occlusion process

Interocular transfer of a pattern and of a black-white discrimination was measured in albino rats under shock motivation. Ss exhibited a reliable interocular decrement for either problem. The effectiveness of the black vinyl-acrylic contact occluders used to blind Ss was evaluated by presenting 20 test trials with both eyes occluded after training and interocular testing. Despite the complete superficial coverage of the eye, performance was somewhat above chance on the black-white problem, suggesting that the interocular transfer deficit is not only reliable, but also sizeable for both problems. An error analysis showed that the interocular decrement was not due to the introduction of a tendency which had been reported by previous experimenters, for monocular rats to go in the direction of the uncovered eye.

Interocular interaction of conflicting discrimination habits in the albino rat: A preliminary report

Shock-motivated albino rats promptly learned a reversal habit via one eye while retaining the original habit via the opposite eye, even though they previously had shown veridical interocular transfer in the same situation. Binocular tests revealed marked individual variations in conflicting-habit dominance.

Acquisition and retention of monocular discriminations in rats as a function of relevant (reversal) or irrelevant opposite-eye training

Albino rats retained a monocular pattern discrimination even after interpolated mastery of a reversal or a black-white discrimination via the opposite eye. In the first experiment, a second-eye reversal problem was acquired more rapidly than the original pattern problem. The second experiment showed that monocular training on a black-white problem has a marked facilitatory effect on subsequent acquisition of a pattern discrimination with the opposite eye.

Assessment of the generality of enhanced learning following unilateral lesions of posterior neocortex in rats

Sixty albino rats with unilateral lesions of striate cortex, unilateral orbital enucleations, or sham operations were trained on black-white and horizontal-vertical discriminations, with order of problem presentation counterbalanced. Mastery of the initially acquired discrimination greatly enhanced acquisition of the second; however, the previously 4 reported enhancement of acquisition associated with unilateral striate ablation proved to be of limited generality: it occurred only during initial learning of the horizontal-vertical problem.

Interocular transfer in albino and pigmented perinatal guinea pigs

Interocular transfer of a pattern discrimination was measured in albino and pigmented guinea pigs ranging from 1 to 37 days of age when training began. Transfer was unrelated to albinism, but significantly more transfer occurred in a 14 to 37-day old group of Ss than in a 1-day old group. These findings are related to previous anatomical and electrophysiological observations concerning the functioning of optic uncrossed fiber systems.

Interocular transfer in albino rats as a function of forebrain or forebrain plus midbrain commissurotomy.

Abstract An attempt was made to determine whether interocular transfer of a black-white discrimination would be blocked by section of interhemispheric pathways. Thirty-six albino rats were equally divided into three surgical treatment groups: sham-operate, corpus callosum-section, or corpus callosum-plus superior colliculus- and posterior commissure-section. Before statistical analyses of the behavioral data were performed, the animals were reassigned to appropriate groups based upon histological examination of the lesions. The multiple-commissurotomized animals showed nearly complete incidental section of hippocampal and habenular commissures, while the callosal-sectioned and sham-operated animals had comparatively little incidental damage. The callosal-sectioned and sham-operated animals exhibited interocular transfer of a black-white discrimination, although the callosal-sectioned animals showed less transfer than the sham operates. The multiple-commissurotomized animals showed no transfer; they also made reliably more errors during acquisition via the second eye (i.e., during the test for transfer) than either the sham operates or corpus callosal-sectioned animals. These results are comparable to previous research on cats. In addition, there were no differences in the initial rates of acquisition of the black-white discrimination between the three groups; these data suggest that section of the commissures does not impair the normal mechanisms needed to acquire the discrimination.

Enhanced pattern discrimination learning following unilateral damage to posterior cortex in rats

Rats with unilateral damage to the posterior cortex, including the “visual” cortex, learned a monocular pattern discrimination substantially more quickly than did an unoperated group. A unilaterally blinded group did not differ reliably from unoperated animals.

Assessment of the contact eye cover as an effective method of restricting visual input

In the wake of several studies that have cast doubt upon the effectiveness of contact eye covers in restricting vision, we performed a series of five experiments to the end of achieving reversible blinding of the albino rat. The data of Experiment 1 indicated that the contact eye cover can be as effective as a rubber cup in restricting visual input. In Experiment 2, animals that were fitted binocularly with opaque eye covers performed as if blind on a task involving acquisition of pattern discrimination. In Experiment 3, binocular coverage with the opaque eye cover resulted in chance performance across 300 trials of a previously acquired pattern-discrimination habit. In Experiment 4, the base diameter of the eye cover was found to be a critical factor: Performance of a previously acquired brightness discrimination was reduced to chance levels by contact eye covers that approximated 7.0 mm in diameter. In Experiment 5, a smaller eye cover (6-mm diam) had no effect in limiting the visually evoked electrocortical response of the albino rat, while an eye cover of 7.2-mm diam produced a reliable attenuation of the response. The collective results indicate that appropriately fabricated contact eye covers are a viable means of restricting visual input and may justifiably be considered contact occluders.