Metastable Oscillatory Modes Emerge from Synchronization in the Brain Spacetime Connectome

Cabral, Castaldo et al. — Nature Communications Physics 5, 184, 2022.

Why I cared. The brain’s transient rhythms are everywhere in MEG, yet where do slow, collective rhythms come from if neurons produce fast, short-lived oscillations? The delay-coupling idea was too elegant not to test.

What we did. We took damped oscillators — standing in for short-lived gamma generated in local circuits — coupled them through the real diffusion-tractography connectome with conduction delays, and swept the global coupling strength and conduction speed.

What we found. In a critical regime, metastable oscillatory modes emerge at sub-gamma frequencies, organised in space and time, and they approximate the MEG power spectra of 89 healthy people at rest. Their frequency, duration and scale — and the envelope connectivity — are set by a couple of global parameters, with the connectome left unchanged. Slow collective rhythms can be built from fast local ones, purely through delays in the spacetime structure.

What it opened. If global parameters tune these modes on a fixed connectome, what moves them in a living brain — and what does it really mean for a rhythm to be metastable rather than simply on or off?