6.6 A note on the barn owl

The barn owl is the auditory-research animal par excellence, because it can localize sounds with a precision of about 1 degree in azimuth and elevation — better than any other vertebrate, and good enough to strike a mouse in total darkness. The owl’s nucleus laminaris (the avian MSO equivalent) is a textbook Jeffress-style delay-line structure, and Mark Konishi’s lab spent decades elucidating exactly how it works.

The owl’s azimuthal localization is built from ITDs computed in nucleus laminaris just like the mammalian MSO. But because the owl can also localize in elevation (using the ILDs created by its facial-disc asymmetry), and because its ITD-and-ILD information is segregated in the brainstem and then combined into a topographic map of auditory space in the external nucleus of its inferior colliculus, the owl ends up with what is essentially a spatial coordinate system that we mammals can only approximately approximate. The two species converge on the same problem from different evolutionary directions, with results that are mutually illuminating.