Evidence for a third primary visual area in the telencephalon of the pigeon.

The presence of a visual projection area in the caudolateral telencephalon of the pigeon was demonstrated with evoked potentials. Shorter latencies were recorded in this region than in both the classic primary telencephalic visual projection areas, the Wulst and the ectostriatum. The evoked potentials from the caudolateral telencephalon were not due to electrotonic conduction either of potentials from the underlying tectum or of electroretinograms from the eyes, which border on the telencephalon. Projections from the Wulst and the ectostriatum could also be excluded as sources of the short latency visual evoked potentials from the caudolateral telencephalon. The presence of a third visual projection to the telencephalon in the pigeon is discussed in relation to known visual projections to the telencephalon in other vertebrates.