Theta-band phase tracking in the two-talker problem

• We assess two predictions of the selective entrainment hypothesis.
• Neural oscillations show greater phase-locking to attended speech.
• Phase-locking is enhanced during successful encoding of speech content.

It is usually easy to understand speech, but when several people are talking at once it becomes difficult. The brain must select one speech stream and ignore distracting streams. We tested a theory about the neural and computational mechanisms of attentional selection. The theory is that oscillating signals in brain networks phase-lock with amplitude fluctuations in speech. By doing this, brain-wide networks acquire information from the selected speech, but ignore other speech signals on the basis of their non-preferred dynamics. Two predictions were supported: first, attentional selection boosted the power of neuroelectric signals that were phase-locked with attended speech, but not ignored speech. Second, this phase selectivity was associated with better recall of the attended speech.