Organization of the Visual Pathways and Visual Lateralization in the Chick

Abstract

This thesis reports research on the organization of the bilateral thalamo-Wulst (thalamofugal pathway) and tecto-rotundal tectofugal pathway) projections in the chick using fluorescent retrograde tracers. It also examines asymmetry of these projections and the differential contributions of the two visual pathways to functional lateralization. The research began by examining the abilities of various fluorescent tracers to label the bilateral projections of the two visual pathways. In the thalamofugal pathway, rhodamine B isothiocyanate (RITC), Fluorogold (FG) and True blue (TB) were found to label both the ipsilateral and contralateral projections. However, differential labelling effects 'were found in the tecto-rotundal projections: RITC and red (rhodamine) beads labelled both the ipsilateral and contralateral projections, but FG, TB and green (fluorescein) beads labelled only the ipsilateral projections. It was found that FG and TB (and maybe also green beads) were taken up by the nerve endings, were transported possibly to the point where the axon collateral branches from the main axon, but failed to be transported to the cell body.