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.

Decreases in Stuttering Frequency as a Function of Continuous and Contingent Forms of Auditory Masking

This experiment examined the effects of continuous and contingent white noise masking upon the speech of 10 stutterers. The methodology equated the frequency of masking opportunities during (1) noise onset made contingent upon phonation, and (2) noise cessation made contingent upon phonation. A continuous noise condition and a no-noise control condition were also included. All noise conditions produced significantly less stuttering than the no-noise control condition. The three masking conditions yielded approximately the same reductions in the frequency of stuttered responses. Fluency enhancement by the various masking conditions could possibly be explained by reflex functions of the middle ear muscles.