Selective auditory attention effects in tonotopically organized cortical areas: A topographic ERP study

This study reinvestigates some aspects of the neurophysiological mechanisms of auditory selective attention, by testing the hypothesis that auditory attention can exert a selective control over the sensory processing of acoustic stimuli in tonotopic auditory cortex. Event-related potentials (ERPs) were recorded from human subjects while they listened selectively to a tone sequence in one ear and ignored a concurrent sequence of a different frequency in the opposite ear. The tone frequencies were 500, 1,000, 2,000, or 4,000 Hz in separate sequences, and were delivered at a constant rate of one every 800 ms. The effects of attention were analyzed in the difference waves obtained by subtracting ERPs to ignore tones from those of the same tones when attended. The earliest effect of attention (70–80 ms post-stimulus) was found to present the same spatio-temporal organization as the obligatory, sensory-evoked N1 wave, with similar tonotopic changes in scalp distribution with the tone frequencies. At longer latencies, two other attentional effects were observed, of probable endogenous origin: one around 175 ms post-stimulus, possibly originating from non-tonotropic auditory cortex, and the latest one (after 300 ms) from non-specific areas. The results support the hypothesis of a genuine sensory gating mechanism for auditory attention, taking place in tonotopic auditory cortex at an early stage of sensory processing, even in low attentional load conditions. © 1995 Wiley-Liss, Inc.