Narrowband oscillations (NOs), Broadband Arrhythmic Activity (BAA) and paroxysmal Salient Events (SEs: transient amplitude fluctuations above a threshold) are valuable conceptualizations extensively used to interpret magneto- (MEG) and electro- (EEG) encephalographic activity, yet, these perspectives have progressed in parallel without a consensus rationale linking them. Here, we bridge that divide by introducing the Spectral Group Delay Consistency (SGDC) framework to provide an analytical description of the signal-level conditions under which NOs and BAA coalesce into transient salient events. This is important since SEs may modulate long-range dependencies across timescales, with preliminary evidence suggesting that they may constitute a hallmark of cognitive decline in dementia-spectrum disorders, including Alzheimer’s and Parkinson’s diseases.

We combined signal processing and analytical tools to reveal how transient phase-structured oscillatory (alpha) bursts contribute to long-range coordination during rest. Our analysis extends the communication-through-coherence hypothesis to the transient domain, and offers a comprehensive picture of how SEs arise from NOs and BAA via the SGDC mechanism, integrating these fundamental components of MEG/EEG activity.