Evidence for visual mapping in the peduncle lobe of octopus.

The first use of horseradish peroxidase in the central nervous system of a cephalopod revealed apparent topographic connections between optic and peduncle lobes in octopus. Optic lobe efferent fibers within the peduncle lobe neuropil and labeled cells in the peduncle lobe exhibited alignment along the anteroposterior and dorsoventral axes of the peduncle lobe. The location and number of labeled peduncle lobe cells depended on the extent of the injection site in the optic lobe.