Reduced low‐frequency power and phase locking reflect restoration in the auditory continuity illusion

• Published in: The European journal of neuroscience 2018-10, Vol.48 (8), p.2849-2856
• Main Authors: Kaiser, Mathis, Senkowski, Daniel, Roa Romero, Yadira, Riecke, Lars, Keil, Julian
• Format: Article
• Language: English
• Subjects: auditory perception; Cortex (auditory); EEG; Frequency dependence; ITC; Noise; Oscillations
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.13861

Interruptions in auditory input can be perceptually restored if they coincide with a masking sound, resulting in a continuity illusion. Previous studies have shown that this continuity illusion is associated with reduced low‐frequency neural oscillations in the auditory cortex. However, the precise contribution of oscillatory amplitude changes and phase alignment to auditory restoration remains unclear. Using electroencephalography, we investigated induced power changes and phase locking in response to 3 Hz amplitude‐modulated tones during the interval of an interrupting noise. We experimentally manipulated both the physical continuity of the tone (continuous vs. interrupted) and the masking potential of the noise (notched vs. full). We observed an attenuation of 3 Hz power during continuity illusions in comparison with both continuous tones and veridically perceived interrupted tones. This illusion‐related suppression of low‐frequency oscillations likely reflects a blurring of auditory object boundaries that supports continuity perception. We further observed increased 3 Hz phase locking during fully masked continuous tones compared with the other conditions. This low‐frequency phase alignment may reflect the neural registration of the interrupting noise as a newly appearing object, whereas during continuity illusions, a spectral portion of this noise is delegated to filling the interruption. Taken together, our findings suggest that the suppression of slow cortical oscillations in both the power and phase domains supports perceptual restoration of interruptions in auditory input. We investigated continuity ratings, EEG power changes and phase locking in response to auditory stimuli that were either continuous or interrupted and either fully or partially masked. We observed attenuated 3 Hz power for continuity illusions, likely reflecting a blurring of auditory boundaries. We further observed increased phase locking for fully masked continuous tones, which may reflect the registration of the mask as a newly appearing object, not elicited during continuity illusions.