The Horizontal Optokinetic Reflex of the opossum ( Didelphis marsupialis aurita): Physiological and Anatomical Studies in Normal and Early Monoenucleated Specimens

• Published in: Vision research (Oxford) 1997-05, Vol.37 (9), p.1207-1216
• Main Authors: NASI, J.P, VOLCHAN, E, TECLES, M.T, BERNARDES, R.F, ROCHA-MIRANDA, C.E
• Format: Article
• Language: English
• Subjects: Animals; Behavioral psychophysiology; Biological and medical sciences; Eye Enucleation; formula omitted; Fundamental and applied biological sciences. Psychology; Monocular enucleation; Neural Pathways; Nucleus of the optic tract; Nystagmus, Optokinetic - physiology; Opossums - physiology; Optokinetic nystagmus; Pattern Recognition, Visual - physiology; Plasticity; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reflexes; Retina - anatomy & histology; Superior Colliculi - anatomy & histology; Superior Colliculi - physiology; Time Factors; Vision, Monocular
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(96)00137-X

In the opossum the symmetrical binocular horizontal optokinetic nystagmus gives way to an asymmetrical monocular reflex: the nasotemporal (NT) stimulation yielding lower gain than the temporonasal (TN). In adults, monocularly enucleated at postnatal days 21–25 (pnd 21–25), the gain of NT responses is markedly increased, approaching that of TN. Severe cell loss was detected in the nucleus of the optic tract (NOT) on the deafferented side in early monoenucleated specimens. In normal animals retinal afferents to the NOT are all crossed, while in animals enucleated at pnd 21–25 sparse uncrossed retinal elements were observed. Although this abnormal projection might influence the increase NT response in this subgroup, it is argued that the increased symmetry in monoenucleated opossums may be the result of changes mediated by the commissural connection between both NOTs. © 1997 Elsevier Science Ltd. All rights reserved.