Ho, H.Tam, David Burr, Alais, D., Morrone, M. C.
Oscillations of Sensitivity and Response Bias in Auditory Perception
Département d'études cognitives, École normale supérieure
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.