The cortical entrainment to a background speaker modulates the comprehension of a target speech in a cocktail party environment
It has recently been found that the cortical tracking of a target speaker plays a functional role in speech processing. In particular, we showed that the modulation of the cortical entrainment to the speech envelope through tACS in the theta band modulates the comprehension of speech in noise. However, the functional role of cortical tracking of a distractor voice remained unclear. Here we therefore studied the effect of tACS with the envelope of a distractor voice on the comprehension of a target speech.Eighteen right-handed, healthy participants with normal hearing participated. We applied tACS with either the distractor or the target envelope filtered in theta band, while measuring the speech comprehension at the individual SNR corresponding to a speech comprehension of 50% in the presence of a distractor voice. We discovered that both types of neurostimulation modulate speech comprehension in a similar way. Particularly, they led to a significant modulation that varied sinusoidally, at the longest possible period. Moreover, the modulation caused by both types of tACS had a significantly consistent phase dependency across participants. Our results show that the distractor speaker is tracked in the brain, and that modulation of this tracking influences comprehension of the target speaker.