Meynert cells are large pyramidal cells at the border between layers V and VI in primary visual cortex(V1). They project to several cortical and subcortical areas, and have been reported to have widespread intrinsic collaterals within VI (Rockland, SFN Abstr 1999). In order to understand further the functional architecture of V1, we are investigating the correlation of intrinsic collaterals of Meynert cells with ocular dominance columns(ODCs). ODCs were demonstrated by optical imaging of the intrinsic signals after visual stimulation in anesthetized monkey. Meynert cell collaterals were labeled by pressure-injected biotinylated dextran amine(BDA). BDA injection was made one week after the imaging experiment, placed in reference surface image of V1. One week after injection, animal was perfused and the tissue was processed for DAB histochemistry. In the analysis, segments of Meynert cell axons were traced from the injection site and/or its vicinity. Four segments were serially reconstructed from within the ...