Cortical convergence originating from domains representing different frequencies in the cat AI

In order to reveal the cortical convergence, two different anterograde tracers were injected in the cat primary auditory cortex (AI). These tracers were located side by side in AI, at loci representing different best frequencies. Patches of labeled fibers were found mainly dorsal and ventral to each injection site. Patches located immediately dorsal and ventral to the injection sites did not overlap each other, but those located most distant from the injection sites overlapped significantly. Areas where the overlapping of labeled fibers were found correspond to the dorsal zone and secondary auditory field. The results suggest that the cortical convergence representing different frequency information takes place outside AI.