phase locking

Phase locking is what happens when a neuron consistently fires its spikes at the same point in a rhythm. Picture a wave rolling up and down over and over — a brain rhythm, or oscillation, is exactly that kind of repeating rise and fall in electrical activity shared by a crowd of nearby cells. Each spot along one cycle of the wave is called a phase: the crest, the trough, the rising slope, and so on. A neuron is phase locked when, cycle after cycle, it tends to spike at one favored phase — for example, always right near the trough — rather than firing at random moments. It is like a dancer who always steps on the same beat of the music instead of stepping whenever.

This matters because the brain can use timing, not just how many spikes there are, to carry information and coordinate work. If many neurons all lock to the same phase of a shared rhythm, their spikes arrive together in tight bunches, which makes their combined signal land more strongly on the cells downstream — good timing acts like good aim. The favored phase can also tag a spike with extra meaning: in the hippocampus, a region that helps build memories of places, cells fire at progressively earlier phases of an ongoing rhythm as an animal moves through a location, so the exact phase encodes where the animal is. Scientists measure how tightly a neuron is locked by collecting the phase at which each of its spikes occurs and checking whether those phases cluster near one value or spread out evenly.