SELECTIVE ATTENTION ENHANCES THE AUDITORY 40-HZ TRANSIENT-RESPONSE IN HUMANS

STUDIES of human auditory1-3 and somatosensory3 modalities have shown that there is an oscillatory response in the gamma-band (at about 40 Hz) frequency which is elicited by either steady state1-3 or transient4 stimulation. The auditory 40-Hz response is generated at least partially in the auditory cortex4,5 as a result of thalamocortical interaction6 and may serve perceptual integration7,8 and conscious perception9. A connection to selective attention has been implied in human10 and animal11 studies, although the evidence is inconclusive12. Moreover, fundamental differences between the human and animal 40-Hz responses13 prohibit generalization. Furthermore, most experiments have used steady-state stimulation during which the brain does not regain its resting state between stimuli as it does when transient stimulation is used14. Here we study the effect of selective attention on the auditory gamma-band (40-Hz) transient response using subjects listening to tone pips presented in one ear while ignoring a concurrent sequence of tone pips in the other ear. The 40-Hz response was larger when subjects paid attention to stimuli rather than ignored them. This attention effect was most pronounced over the frontal and central scalp areas. Our results demonstrate a physiological correlate of selective attention in the 40-Hz transient response in humans.