  Normal-hearing listeners adapt to alterations in sound localization cues.
This adaptation can result from the establishment of a new spatial map of the
altered cues or from a stronger relative weighting of unaltered compared to
altered cues. Such reweighting has been shown for monaural vs. binaural cues.
However, studies attempting to reweight the two binaural cues, interaural
differences in time and level, yielded inconclusive results. In this study we
investigated whether binaural cue reweighting can be induced by a
lateralization training in a virtual audio-visual environment. 20
normal-hearing participants, divided into two groups, completed the experiment
consisting of a seven-day lateralization training in a virtual audio-visual
environment, preceded and followed by a test measuring the binaural cue
weights. During testing, the participants task was to lateralize 500-ms
bandpass-filtered (2-4 kHz) noise bursts containing various combinations of
spatially consistent and inconsistent ITDs and ILDs. During training, the task
was extended by visual cues reinforcing ITDs in one group and ILDs in the other
group as well as manipulating the azimuthal ranges of the two cues. In both
groups, the weight given to the reinforced cue increased significantly from
pre- to posttest, suggesting that participants reweighted the binaural cues in
the expected direction. This reweighting occurred predominantly within the
first training session. The present results are relevant as binaural cue
reweighting is, for example, likely to occur when normal-hearing listeners
adapt to new acoustic environments. Similarly, binaural cue reweighting might
be a factor underlying the low contribution of ITDs to sound localization of
cochlear-implant listeners as they typically do not experience reliable ITD
cues with their clinical devices.
