Specificity of regenerating optic fibres for left and right optic tecta in goldfish

Abstract

RECENT studies¹ on the regeneration and development of the visual nervous system of inframammalian vertebrates have concentrated on the topographic patterning of retinotectal connections, neglecting the problem of what specifies the pathways of large tracts. Embryologically the eye is an outgrowth from the ipsilateral side of the brain, but during development the optic nerve fibres cross the midline and terminate on the opposite side where they “mirror” the topographical disposition of their retinal ganglion cells. Sperry^2,3 proposed that the precise patterning of such neuronal circuits resulted from specific affinities between individual nerve fibres and their target loci within the brain, but recent evidence⁴ suggests that what is important is the preservation of the overall pattern of fibre connections, rather than the position occupied by individual terminals⁵.