Neural correlates of attending speech and non-speech: ERPs associated with duplex perception

This study evaluates whether event-related potentials (ERPs) are modulated by attending to either speech or non-speech within the same duplex stimulus. ERP data show no significant task-dependent differences for the P1 component. Significant amplitude and lateralisation effects were found for the N1 component where more negative responses were measured in the left hemifield for the speech condition. Further significant amplitude, latency and lateralisation effects were found for components P2 and N2. Dipole modelling suggests that a symmetrical pair of generators in the left and right auditory cortex can account for the responses up to around 250 ms for both conditions. A third generator, located in the left anterior cingulate cortex (BA 24), is required to model the response beyond 250 ms in the chirp condition. The results show relatively early task-dependent modulation of responses (N1). The dipole modelling suggests that not separate speech-dedicated processing centres but a modulation of activity in the superior temporal cortex is responsible for the differences seen.