Coupling
Parts of a substrate become coupled when they are repeatedly active together. A retrieval may briefly bring several units into the same context; repeated retrieval, use, and write-back leave a more durable relation. Coupling is therefore a memory of interaction in the medium.
Coupling does not by itself imply agreement. Two ideas may be used together because they reinforce one another, because they conflict, or because a task repeatedly places them side by side. The important observation is that a population has made the relation consequential through use.
These relations let us read more than isolated events. Their changing pattern shows where activity is stabilizing, where contexts continue to meet, and where previously connected work is releasing. At a chosen grain and time window, structurally overlapping frames that remain coupled form what we call resonance. Connected regions of such activity form membranes.
We treat the exact update rule and the choice of measurements as implementation questions. The public concept is simpler: repeated interaction writes structure into a shared medium, and that structure can be observed.