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Abstract:
Humans respond more quickly and accurately to sounds that are
presented at an expected frequency compared to sounds that are
presented at an unexpected frequency. When listeners expect to hear
a target sound at a particular frequency region over a long series
of trials, all sounds presented at that frequency elicit an
enhanced negativity, called the negative difference, in the
auditory evoked potential. Similar but smaller effects have been
observed in trial-by-trial cueing experiments using symbolic visual
cues (Schroger, 1994). We investigated the effects of frequency
selection on the auditory evoked potential in two auditory cueing
experiments. In both experiments, an auditory frequency cue
indicated the most likely frequency of the subsequent target
stimulus. A symbolic auditory cue was used in Experiment 1 whereas
a predictive direct cue was used in Experiment 2. Subjects
responded more quickly to targets appearing at the validly cued
frequency compared to targets appearing at the invalidly cued
frequency. Moreover, differences between the auditory evoked
potentials elicited by validly and invalidly cued targets were
observed over frontocentral scalp regions. The earliest effect
appeared to be an enlargement of the P50 component on valid-cue
trials. Both negative and positive differences were observed at
longer latencies. These results indicate that orienting attention
to a particular frequency on a trial-by-trial basis can influence
the processing of auditory stimuli.
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