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Thresholds for S3 in the on-frequency (filled symbols) and off-frequency (open symbols) precursor conditions as a function of precursor duration. No systematic differences were seen for off-frequency precursors across conditions (including delay, not shown), so a grand average was taken of all off-frequency precursor thresholds. The temporal effect is defined as the difference between on-frequency precursor thresholds and the average off-frequency precursor thresholds (dashed line).
