Attentional modulation of the early cortical representation of speech signals in informational or energetic masking.

It is easier to recognize a masked speech when the speech and its masker are perceived as spatially segregated. Using event-related potentials, this study examined how the early cortical representation of speech is affected by different masker types and perceptual locations, when the listener is either passively or actively listening to the target speech syllable. The results showed that the two-talker-speech masker induced a much larger masking effect on the N1/P2 complex than either the steady-state-noise masker or the amplitude-modulated speech-spectrum-noise masker did. Also, a switch from the passive- to active-listening condition enhanced the N1/P2 complex only when the masker was speech. Moreover, under the active-listening condition, perceived separation between target and masker enhanced the N1/P2 complex only when the masker was speech. Thus, when a masker is present, the effect of selective attention to the target-speech signal on the early cortical representation of the speech signal is masker-type dependent.