An HRP and 3H-apo-HRP study of the thalamic projections to visual cortical areas in the cat.

Double retrograde tracer experiments (HRP, 3H-apo-HRP) were performed to investigate the organization of thalamic neurons projecting to visual cortical areas. The distribution of labelled cells was in agreement with previous findings, showing a topographical and overlapping pattern of these thalamocortical projections. If a restricted thalamic region in the lateralis posterior-pulvinar complex projected into more than one cortical area, the projection neurons to each individual area were intermingled. However, each neuron projected only into one area and there was no anatomical evidence for the presence of neurons projecting to more than one cortical area.