Stepping out of the spotlight: MMN attenuation as a function of distance from the attended location

In this report we present neurophysiological evidence that spatial separation between attended and unattended sound sources influences a listener's ability to register changes in sounds presented outside the focus of attention. Standard and deviant stimuli were presented at three azimuth locations. Participants were asked to press a key whenever they heard a deviant at a designated location. Mismatch negativity waves were generated for deviants at the attended location and were attenuated for deviants occurring 30 degrees away from the attended location. Mismatch negativities were not observed at distances of 60 degrees or more. The results are consistent with a spotlight model of auditory attention in which the processing of stimuli outside the attentional focus is attenuated as a function of increasing distance from the focus.