Learning to discriminate interaural time differences at low and high frequencies.

This study investigated learning, in normal-hearing adults, associated with training (i.e. repeated practice) on the discrimination of ongoing interaural time difference (ITD). Specifically, the study addressed an apparent disparity in the conclusions of previous studies, which reported training-induced learning at high frequencies but not at low frequencies. Twenty normal-hearing adults were trained with either low- or high-frequency stimuli, associated with comparable asymptotic thresholds, or served as untrained controls. Overall, trained listeners learnt more than controls and over multiple sessions. The magnitudes and time-courses of learning with the low- and high-frequency stimuli were similar. While this is inconsistent with the conclusion of a previous study with low-frequency ITD, this previous conclusion may not be justified by the results reported. Generalization of learning across frequency was found, although more detailed investigations of stimulus-specific learning are warranted. Overall, the results are consistent with the notion that ongoing ITD processing is functionally uniform across frequency. These results may have implications for clinical populations, such as users of bilateral cochlear implants.