Evidence that the relative densities of afferents from both eyes control laminar distribution and binocular segregation of retinotectal projections in rats.
In the superior colliculus of normal rodents the crossed retinal projection overlaps the uncrossed projection. The present study describes an abnormal laminar distribution and binocular segregation of the retinotectal afferents induced after the experimental enlargement of the uncrossed retinotectal pathway in pigmented rats. Intraocular injections of anterograde tracers were used to investigate the topographic and laminar organization of retinotectal projections in adult rats given unilateral optic tract lesions at birth. These lesions are known to increase the number of ipsilaterally projecting ganglion cells in the opposite retina. The uncrossed retinal projection to the remaining superior colliculus forms an abnormal band of terminal labeling at the superficial half of the stratum griseum superficiale, markedly different from the laminar distribution of this pathway in unoperated controls. This abnormal uncrossed projection has its maximum density at the rostrolateral quadrant of the tectum. Within this region, the crossed retinotectal projection retracts from the surface of the superior colliculus, leading to partial binocular segregation. The results suggest that both the laminar distribution and the experimental binocular segregation of retinotectal afferents depend on the balance of the densities of the converging pathways from both eyes in the superior colliculus.
Instituto de Biofisica da UFRJ, Rio de Janeiro, Brazil.
C A
CA
Serfaty
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R
Linden
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D005123:Eye / Q000294:innervation*; D006651:Histocytochemistry; D006735:Horseradish Peroxidase; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D012160:Retina / Q000166:cytology / Q000502:physiology*; D013477:Superior Colliculi / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D015348:Vision, Binocular / Q000502:physiology*
D006735:Horseradish Peroxidase