Travelling spindles create necessary conditions for spike-timing-dependent plasticity in humans

Sleep spindles facilitate memory consolidation in the cortex during mammalian non-rapid eye movement sleep. In rodents, phase-locked firing during spindles may facilitate spike-timing-dependent plasticity by grouping pre-then-post-synaptic cell firing within similar to 25 ms. Currently, microphysiological evidence in humans for conditions conducive for spike-timing-dependent plasticity during spindles is absent. Here, we analyze field potentials and unit firing from middle/upper layers during spindles from 10 x 10 microelectrode arrays at 400 mu m pitch in humans. We report strong tonic and phase-locked increases in firing and co-firing within 25 ms during spindles, especially those co-occurring with down-to-upstate transitions. Co-firing, spindle co-occurrence, and spindle coherence are greatest within similar to 2 mm, and high co-firing of units on different contacts depends on high spindle coherence between those contacts. Spindles propagate at similar to 0.28 m/s in distinct patterns, with correlated cell co-firing sequences. Spindles hence organize spatiotemporal patterns of neuronal co-firing in ways that may provide pre-conditions for plasticity during non-rapid eye movement sleep.

Automated summary

Research shows that there is a strong tonic and phase-locked increase in firing and co-firing during spindles, especially those occurring with down-to-upstate transitions, within 25 ms. Co-firing, spindle co-occurrence, and spindle coherence are greatest within approximately 2 mm.