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University of Balamand > Academics > Research > Seminars > Maha Khachab


SUBMITTED BY: Maha Khachab
University of Balamand

ABSTRACT: The developing and adult pattern of retinocollicular and corticocollicular connections were examined in mice to understand the growth of axons to their targets and formation of synapses. The lipophilic fluorescent dye, DiI, was used to compare the development of the cortical projections in phenotypically normal (C57BL/6J) mice to that of anophthalmic 129SV/CPorJ mice. Cortical axons in anophthalmic mice found their targets and established laminar specificity similar to those of cortical axons in normal mice despite the absence of the retinal projection. Cortical axons in normal mice reached the superior colliculus before those in anophthalmic mice and also had a faster rate of growth within the colliculus. Unlike cortical axons in normal mice, those in anophthalmic mice formed a disperse bundle in the stratum opticum. Axons labeled by focal applications of DiI into area 17 terminated in a larger and more medial area in anophthalmic mice than in normal mice. Thus, retinal axons are not essential for cortical axons to reach the superior colliculus, but they may have a role in organizing the growth of later arriving cortical axons. Furthermore, cortical axons can terminate in the superior colliculus with a coarse topography when retinal axons are absent, but they cannot form a topographically refined projection.

Keywords: superior colliculus, topographic specificity, laminar specificity, retina, corticocollicular growth, DiI, development.
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