Why do sounds we make ourselves seem quieter to the brain?
Before a self-triggered sound, auditory cortex showed stronger alpha rhythms, and people with a bigger alpha boost showed a bigger dampening of the brain's response to the sound.
Source
The role of brain oscillations in predicting self-generated sounds
Study at a glance
- Design
- Human experiment — Within-subject MEG experiment comparing self-triggered tones (finger lift) with computer-presented tones at a regular or jittered rhythm, analysed as evoked fields and source-level time-frequency activity in right auditory cortex.
- N
- N=14 · 14 right-handed healthy volunteers; roughly 100 trials per condition before artefact rejection.
- Population
- Healthy young adults (mean age 22.6) in Glasgow
- Outcome
- M100 evoked field amplitude; pre- and post-stimulus alpha, beta and gamma power and phase locking in auditory cortex, and their correlations
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Fourteen volunteers heard the same brief tone under different conditions while MEG recorded their brain activity: in the active condition the tone played immediately when they lifted a finger, and in passive conditions the computer played it either at a steady three-second rhythm or at unpredictable intervals. The authors reconstructed activity in right auditory cortex and compared evoked responses, oscillatory power and phase locking between self-generated and regular passive tones, then correlated these measures across people and, in the unpredictable condition, across single trials.
What they found
Self-generated tones produced a smaller M100 response, replicating sensory attenuation. Starting about 400 ms before the tone, alpha power (around 10 Hz) was higher in the active condition, and larger alpha increases went with stronger attenuation (rho = -0.74). After the tone, the active condition showed reduced broadband power including gamma and reduced alpha/beta phase locking, while the theta component that carries most of the evoked response did not differ. Higher pre-stimulus alpha predicted lower post-stimulus gamma, both across people and trial by trial, and early gamma appeared to precede alpha/beta phase resetting.
The limits
What it doesn't show
The sample was small, so the across-participant correlations are imprecise, as their wide confidence intervals show. Analysis was restricted to one voxel in right auditory cortex to avoid contamination from the left motor cortex, so it says little about the left hemisphere or wider networks. The findings are correlational: alpha, gamma and phase changes are interpreted as prediction precision, prediction error and feedback, but these roles were not manipulated directly, and the authors admit the brief post-stimulus effects may not be true oscillations. The active condition also involves movement and attention differences that are not fully separated from prediction itself.
Key terms
- Sensory attenuation
- The reduced brain response to sensations we cause ourselves compared with identical external ones.
- Forward model / efference copy
- A copy of a motor command used to predict the sensory consequences of an action, so they can be cancelled or discounted.
- M100
- The MEG auditory response peaking about 100 ms after a sound, the magnetic counterpart of the EEG N1.
- Alpha oscillations
- Rhythmic activity around 8-12 Hz often linked to inhibition or reduced excitability of a brain region.
- Phase locking
- How consistently the phase of an oscillation lines up across trials relative to stimulus onset.
- Prediction error
- In predictive coding, the mismatch between expected and actual input that is passed up the processing hierarchy.
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Quiz yourself
How were self-generated sounds produced in this study?
Common questions
Why include a passive condition with jittered timing?
Unpredictable timing makes readiness for the sound vary from trial to trial, letting the authors test whether the same alpha-gamma relationship appears within people even without self-generation.
Why analyse only right auditory cortex?
Participants moved their right finger, so activity from the left motor cortex could leak into estimates for the nearby left auditory cortex.
Does higher alpha mean the brain is ignoring the sound?
The authors interpret it as turning down the gain of auditory cortex because the sound is predicted, a form of active inhibition rather than inattention.
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