Oscillations of sensitivity and decision criterion in audition

Visual perceptual performance fluctuates rhythmically over time,
reflecting the influence of endogenous brain oscillations in the theta
(~4–7 Hz) and alpha frequency band (~8–12 Hz). In two behavioural
studies, we show that these oscillations are not unique to vision but
also present in audition. Using signal detection theory (SDT), we
demonstrate that auditory sensitivity and criterion (changes in
decision boundary) oscillate at different frequencies: ~6 Hz for
sensitivity and ~8 Hz for criterion, implying distinct underlying
mechanisms (Experiment 1). Consistent with visual findings, the
modulation of sensitivity in left and right ears is in antiphase,
suggestive of an attention-like mechanism that samples alternatively
from the two ears. To test whether modulation of criterion reflects a
reverberatory mechanism by which past perceptual history propagates
across trials, we combine serial-dependence and frequency analysis.
Our findings confirm that rhythmic fluctuations in criterion are
contingent on perceptual history: the oscillations (~9 Hz) occur only
for trials preceded by a target to the same ear (Experiment 2). We
propose that each auditory stimulus elicits an oscillating memory
trace (a ‘perceptual echo’), specific to the ear of origin, which
subsequently biases perceptual decisions (in that same ear), resulting
in positive sequential effects.