Spatial Masking of the Delayed Sound Motion: EEG and Behavioral Measures

This study investigated the effect of simultaneous masking at different angular distances between stationary maskers and signals with delayed motion onset on the perceived location of signal trajectory endpoints and the strength of the global field power (GFP) in evoked responses in the electroencephalogram. Stimulus positions were manipulated through interaural intensity differences. Evoked responses to the signal's onset and offset were maximally suppressed when the masker position matched the signal’s starting and ending points, respectively. As the distance increased, the responses partially recovered, indicating a spatial release from masking. The maximum suppression of the motion onset response occurred when the lateral or central masker was located at the end of the movement trajectory. Despite complete or partial suppression of the GFP, the listeners were able to localize the test signals under masking conditions. However, the perceived signal trajectories shortened, and their perceived positions shifted away from the masker. The GFPs were more susceptible to energetic masking, while behavioral responses were more robust in recognizing motion, as they relied on the activity of broad neural networks involved in the integration of sensory information over a longer time period.