J. Neurophysiol. 114:1862-1873, 2015. doi:10.1152/jn.00644.2015 Accepted 24 July 2015.

Maps of interaural delay in the owl's nucleus laminaris.

C. E. Carr, S. Shah, T. McColgan, G. Ashida, P. T. Kuokkanen, S. Brill, R. Kempter, H. Wagner.

Axons from the nucleus magnocellularis (NM) form a presynaptic map of interaural time differences (ITD) in the nucleus laminaris (NL). These inputs generate a field potential that varies systematically with recording position and can be used to measure the maps of ITD in NL. In the barn owl, the representation of best ITD shifts systematically in NL, forming a continuous, smoothly overlapping map of ITD. Iso-ITD contours are therefore not parallel to the NL border. Frontal space (0°) is, however, represented throughout, and thus over-represented with respect to the periphery. Measurements of presynaptic conduction delay, combined with a model of delay line conduction velocity, reveal that conduction delays can account for the mediolateral shifts in the map of ITD.