Project Summary In order to accurately perceive the world and respond accordingly, the brain has to deal with noise inherent in sensory cues. One method is for the brain to learn which cues are reliable across contexts and rely on these cues in the future. Previous studies have demonstrated that sensory systems are able to actively learn recent statistics underlying cue reliability and adapt to short term changes. However, relatively little is known about whether and how sensory systems adapt to natural statistics of sensory cues that are expected to be permanent. While humans display biases based on long term patterns of sensory cue statistics, the neural mechanisms underlying this are unknown. To address these knowledge gaps, this proposal will investigate whether and how anticipated reliability of binaural spatial cues determines sound localization of barn owls. Barn owls compute the interaural time difference (ITD) to determine azimuthal location. Previous work showed that the signal-to-noise ratio of ITD varies across frequencies in a location dependent manner, based on the acoustical properties of the head. Thus, certain frequencies convey more reliable ITD cues for sounds from a given location, and the neural tuning in the midbrain is optimized to reflect this pattern. This provides a system where the reliability of natural acoustic cues is represented, allowing for the investigation of the effect of anticipating sensory statistics on perceptual discriminability and how it is learned. Recent work by our group has shown evidence that human auditory perception is also shaped by ITD statistics, potentially allowing the properties of neural coding investigated in this project to explain the bases of these findings. The overall hypothesis is that barn owls learn to anticipate cue reliability during juvenile critical periods, leading to biases in neural and behavioral processing. Behavioral and electrophysiological approaches along with computational methodology will be used to test this hypothesis. Experiments outlined in Aim 1 will determine whether barn owls show better sound discrimination for frequencies anticipated to be reliable. Aim 2 will investigate whether and how the neural population displaying the pattern of ITD-frequency tuning described in the midbrain explains spatial discriminability. Novel multi-unit recordings in the midbrain in vivo along with computational techniques will be used to address this. Aim 3 will elucidate the capacity of the barn owl to learn altered forms of cue reliability, by changing the acoustical properties of the owl’s head at different stages of development. Altogether, this proposal will provide understanding on the mechanisms used to deal with long term patterns of cue reliability. The data will offer insight into how the auditory system learns the natural statistics underlying sensory noise to optimize perception, as well as its capacity to adapt to unanticipated changes.