Search PubMed⌕ Search

Biomedical subjects

J M Sprague

Publications and source records attributed to J M Sprague.

42 records · Page 3Linked to original sources
PubMed1966

Interaction of cortex and superior colliculus in mediation of visually guided behavior in the cat.

Total contralateral hemianopia follows unilateral removal of the entire occipito-temporal neocortex in the cat. This deficit is classically ascribed to interruption of visual radiations serving cortical function ("cortical blindness") and is considered permanent. Return of vision to the hemianopic field after subsequent removal of the superior colliculus contralateral to the cortical lesion demonstrates that neither assumption is correct. The initial hemianopia is apparently due to depression of function of the colliculus ipsilateral to the cortical lesion, a de- pression maintained by influx of inhibition from the crossed colliculus. Thus, removal of the contralateral tectum, or splitting of the collicular commissure, abolishes this inhibition and allows the return of function in the ipsilateral colliculus, and with it the recovery fronm hemianopia. These findings emphasize that visually guided behavior is mediated at both cortical and midbrain levels, and that there is a marked interaction between these sites.

Animals↗
PubMedDate not supplied

Immediate postoperative retention of visual discriminations following selective cortical lesions in the cat.

Cats were trained preoperatively for brightness discrimination, and 7 pattern and form discriminations, and then retested for preoperative retention on each discrimination. Cortical lesions were then placed in areas 17 and 18 in one group (4 cats), in areas 17, 18 and 19 in another group (3 cats), and in suprasylvian cortex (areas 7, 21, and parts of 19, 5 and the lateral suprasylvian cortex) in a third group (4 cats). Results are also reported for a fourth group with extensive suprasylvian lesions, to which was added an unintended undercutting of areas 17 and 18 (4 cats). While during original preoperative learning the training continued until a fixed, stringent criterion of performance was attained, both preoperative and postoperative retention was tested in short sessions, involving a limited number of trials and a less stringent statistical criterion (significant run). After extensive removal of areas 17 and 18, all cats behaved as though following the cortical lesion they could immediately recognize the discriminative stimuli as efficiently as before, with no need for retraining. On the contrary, the group with areas 17, 18 and 19 lesions showed a substantial postoperative loss of all discriminations, and especially for the more difficult form discriminations, the reattainment of a significant level of performance was hard or impossible within the allotted number of trials. Also in the group with limited suprasylvian lesions, postoperative retention was generally impaired, but the reacquisition of efficient performance was superior to that of the previous group. Finally, large suprasylvian lesions encroaching on the white matter under areas 17, 18 and 19 proved disruptive for all discriminative capacities, both in retention and in relearning. The excellent retention of all discriminations following areas 17 and 18 lesions once again shows that these areas are by no means essential for complex vision in the cat. In addition, the results strongly indicate that the high-level visual capacities of destriate cats are not due to reorganization of readaptation processes occurring in extrastriate areas after a 17/18 removal. The clear-cut retention deficits which were present in cats with cortical lesions more extensive than areas 17 and 18 or outside of the latter areas prove the essential participation of extrastriate cortical areas in visual discrimination including form. However, the distribution of functions among the various visual cortical areas in visual discrimination remains poorly understood.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗