Spatial attention to central and peripheral auditory stimuli as indexed byevent-related potentials

Young adult subjects attended selectively to brief noise bursts delivered i n free-field via central and peripheral arrays of four loudspeakers each th at were arranged along a semi-circle extending from the midline to 90 degre es right of center. Frequent "standard" stimuli (90%) and infrequent "targe t/deviant'' stimuli (10%) of increased bandwidth were delivered at a fast r ate in random order and equiprobably from all eight speakers. In separate r uns, the subject's task was to selectively attend to the center or rightmos t speaker, and to press a button to the infrequent "target" stimuli occurri ng at the designated (spatial) location. Behavioral detection rates and con currently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sourc e. The attentional gradients were steeper for the central than the peripher al array, indicating that attention can be more sharply focused upon sound sources directly in front of the listener. The ERP data suggested that sele ction for location is accomplished in two distinct stages, with an initial broadly tuned filtering, followed by a more narrowly focused selection of a ttended-location deviants. (C) 1999 Elsevier Science B.V. All rights reserv ed.