Effect of unilateral decortication on inhibitory interactions of the superior colliculus in the cat
Buchtel, H.A.; Camarda, R.; Rizzolatti, G.; Scandolara, C.
Bollettino della Societa Italiana di Biologia Sperimentale 54(1): 93-98
1978
ISSN/ISBN: 0037-8771 PMID: 737055 Document Number: 128807
Experiments were conducted on 17 cats unilaterally decorticated to produce a stable contralateral homonymous hemianopsia. The responses of the neurons of the colliculus contralateral to the lesion and of those ipsilateral to the lesion were studied. Cortical ablation alters the inhibitory collicular processes that normally appear upon presentation of a new stimulus. A stimulus presented in the blind half-field cannot inhibit the neurons excited by stimuli placed in the normal visual field and weakens only moderately the responses to stimuli placed in the blind half-field. A stimulus presented in the normal half-field not only diminishes the responses to a stimulus that appears in that half-field, but also the responses to the stimulus that appears in the blind half-field. An unbalancing exists in the responses of both colliculi which reflects a change in the force of the intercollicular inhibition. This change appears in accord with Sprague's behavioral data, indicating that the hemianopsia following a cortical lesion is due to an inhibition of the colliculus ipsilateral to the lesion by the opposite colliculus.