Fifty Years After: The N1 Effect Travels Down to the Brainstem

Fifty years ago, it was reported that selective attention affects the N1 wave in auditory event-related potentials. We revisited the original study design but integrated the state of the art knowledge on short auditory stimuli and neural signal processing. In particular, one series of tone bursts has been replaced by chirp stimuli which are optimized to evoke consistent brainstem potentials at low and medium stimulation levels. Auditory selective attention affected the chirp- evoked response in subcortical structures, even at level of the inferior colliculi. A single-trial time-frequency analysis of the full-range (0-250ms) event-related potentials showed that selective attention increases the spectrotemporal consistency across trials in the corticofugal auditory pathway, at least from the N1 wave down to the auditory brainstem response.