Neural Speech-Tracking During Selective Attention: A Spatially Realistic Audiovisual Study

Paying attention to a target talker in multi-talker scenarios is associated with its more accurate neural-tracking relative to competing non-target speech. This “neural-bias” to target speech has largely been demonstrated in experimental setups where target and non-target speech are acoustically controlled and interchangeable. However, in real-life situations this is rarely the case. For example, listeners often look at the talker they are paying attention to while non-target speech is heard (but not seen) from peripheral locations. To enhance the ecological-relevance of attention research, here we studied whether neural-bias towards target speech is observed in a spatially realistic audiovisual context, and how this is affected by switching the identity of the target talker. Group-level results show robust neural-bias towards target speech, an effect that persisted and generalized after switching the identity of the target talker. In line with previous studies, this supports the utility of the speech-tracking approach for studying speech processing and attention in spatially realistic settings. However, a more nuanced picture emerges when inspecting data of individual participants. Although reliable neural speech-tracking could be established in most participants, this was not correlated with neural-bias or with behavioral performance, and >50% of participant showed similarly robust neural tracking of both target and non-target speech. These results indicate that neural-bias toward the target is not a ubiquitous, or necessary, marker of selective attention (at least as measured from scalp-EEG), and suggest that individuals diverge in their internal prioritization among concurrent speech, perhaps reflecting different listening strategies or capabilities under realistic conditions. Significance Statement This work contributes to ongoing efforts to study the neural mechanisms involved in selective attention to speech under ecologically relevant conditions, emulating the type of speech materials, multisensory experience, and spatial realism of natural environments. Group-level results show that under these more realistic conditions, the hallmark signature of selective attention – namely the modulation of sensory representation, and its robustness to switches in target-identity – is conserved, at least at the group level. At the same time, results point to an underlying diversity among participants in how that this modulation manifests, raising the possibility that differences in listening strategies, motivation or personal traits lead to differences in the way that individuals encode and process competing stimuli, under ecological conditions.