Passively induced contextual plasticity in sound localization in real and virtual environments

Two experiments examined a localization aftereffect, called contextual plasticity (CP), induced by repeated exposure to transient stimuli presented from a fixed location. The first experiment tested whether passive exposure to the context is sufficient to induce CP in a reverberant classroom. The second experiment tested it in a virtual environment (anechoic or reverberant). Targets (2 ms noise bursts) and adaptors (trains of 12 such bursts) were presented on separate interleaved trials and subjects localized the targets while passively listening to the adaptors. The passively received adaptor caused responses to the targets to be displaced by up to 16° away from the adaptor location. This effect was strongest and fastest in the virtual anechoic environment, while only reaching 5° in real reverberation. Response standard deviations were also affected, increasing in the real environment, while having a complex effect in the virtual environments. Finally, information transfer rate was evaluated, showing that target spatial resolvability decreased near the adaptor location in all environments. Overall, these results show that passive listening to the context is sufficient to induce CP. However, the effect is exaggerated in virtual environments, where listeners might modify their localization strategy, using the adaptor as an anchor, which causes additional performance deterioration.