Attention modulates the cortical representation of speech sounds in the spatial release from informational masking

Spatial separation of multiple talkers reduces listener confusion (i.e., informational masking), improving speech processing. This spatial release from informational masking is thought to reflect automatic processes of stream segregation and improvements in selective attention. However, the relative contributions of bottom-up and top-down processing and their potential interactions remain unclear. This study investigated the role of attention in the spatial release from informational masking using event-related potentials. Noise-vocoded target words were presented with two-talker noise-vocoded masking babble, and the precedence effect manipulated the spatial cue to isolate effects on informational masking. In separate conditions, participants attended to the sounds to detect target words and ignored the sounds to perform a challenging visual task. Benefits of spatial separation on cortical auditory evoked potentials elicited by target words (N1-P2) were evident regardless of attention condition. Benefits of attending to the sounds were evident at later stages (P2, P3), and exploratory analysis also revealed attentional effects in earlier time windows (P1, late N1). These results showed strong contributions from preattentive bottom-up processing in the spatial release from informational masking. Attention benefitted later stages associated with the cognitive processing of sounds and may modulate early perceptual processing under some listening conditions.