Event-related potentials demonstrate a narrow focus of auditory spatial attention

The distribution of spatial attention across neighbouring sound sources was investigated by assessing event-related potentials (ERPs) to tone probes embedded in natural speech during a selective-attention task. Concurrent speech messages were delivered from the middle positions of two groups of three sound sources in free-field in front of the subject, one to the left and the other to the right of the midline. In each group, the two extreme neighbour loudspeakers were positioned very closely to the middle ones. Brief tone pips were delivered from all locations in a random order. ERPs elicited by the tone probes used to probe the extent of spatial attention showed its narrow focus, one comparable to that suggested by behavioural studies.