Auditory perceptual history is communicated through alpha oscillations

Sensory expectations from the accumulation of information over time exert strong predictive biases on forthcoming perceptual decisions. These anticipatory mechanisms help to maintain a coherent percept in a noisy environment. Here we present novel behavioural evidence that past sensory experience biases perceptual decisions rhythmically through alpha oscillations. Participants identified the ear of origin of a brief sinusoidal tone masked by dichotic white noise, and response bias oscillated over time at ∼9 Hz. Importantly, the oscillations occurred only for trials preceded by a target to the same ear and lasted for at least two trials. These findings suggest that each stimulus elicits an oscillating memory trace, specific to the ear of origin, which subsequently biases perceptual decisions. This trace is phase-reset by the noise onset of the next trial, and remains within the circuitry of the ear in which it was elicited, modulating the sensory representations in that ear.