Attention effects on cortical neural processing in spatial listening

Speech understanding in complex acoustic scenes relies on the formation of and attention to auditory objects. Spatial information is an essential cue in the formation of auditory objects and may facilitate attention-based neural enhancement and suppression of target and non-target speech, respectively. Previous studies have used cortical auditory evoked potentials (CAEP) to measure how attention modulates neural representation of spatially separated auditory objects. The current study further extends this work to investigate how expected and unexpected shifts in spatial location of speech signals affect neural processing of these signals. In the experiment, listeners were directed where to listen with a spatial cue presented from one of five locations (±90, ±45, or 0 deg azimuth); the following target sequence was either presented in the cued location (congruent trials) or from a non-cued location (incongruent trials). We hypothesized that neural responses to target sequences would be enhanced when presented from the cued location, whereas neural responses to incongruent sequences would initially be suppressed before spatial attention was shifted toward the target. Further, we expected the size of this suppression to be proportional to the size of the relative shift between cue and incongruent target.