Effects of Stimulation Rate and Attribute Cuing on Event-Related Potentials During Selective Auditory Attention

Auditory event-related potentials (ERPs) were recorded from subjects who attended selectively to a sequence of tones of one frequency and ignored a comparable sequence of tones having a different frequency and spatial origin. In one condition the tones consisted of randomized sequences of brief tone pips while in a second condition the tones were brief increments in intensity (pedestals) of continuous tones at the two frequencies. The tone pips and pedestals were delivered at comparable interstimulus intervals (ISIs), which were short (250–550 ms) in some runs and long (1250–2750 ms) in others. For both classes of stimuli, the subject's task was to detect occasional “target” tones of a slightly shorter duration than the more frequent “standard” tones. Stimuli of the attended frequency elicited a broad negative ERP component (Nd) relative to the unattended tone ERPs. The Nd wave had a considerably shorter onset latency and was smaller in overall amplitude at the faster rate of stimulation. However, the Nd wave did not differ in latency or amplitude between the tone pip and pedestal conditions at corresponding ISIs, suggesting that a high rate of information delivery is a more important factor in accelerating Nd onset than is the continuous reinforcement of the sensory cues that define the two classes of input.