Furthermore, the phenomenon was reported during both awake and anaesthetized states, and in several cortical areas 7, 15 using a variety of sensory stimuli 7, 10. Neural variability quenching is a robust phenomenon that has been reported in intracellular membrane potential recordings in cats, extracellular recordings of spiking activity in monkeys 7, 8, and in human electroencephalography (EEG) 9, 10, 11, 12, electrocorticography (ECOG) 13, magnetoencephalography (MEG) 11, and functional magnetic resonance imaging (fMRI) recordings 14, 15. This trial-by-trial variability is relatively large before stimulus presentation, and strongly reduced (quenched) approximately 200 ms after stimulus presentation 7. Neural activity is highly variable, such that repeated presentations of an identical stimulus result in variable neural responses across trials 1, 2, 3, 4, 5, 6. These results reveal that neural variability quenching is tightly coupled with stimulus-induced changes in the power of alpha-beta band oscillations, associating two phenomena that have so far been studied in isolation. However, changes in inter-trial-phase-coherence (ITPC) exhibited distinct timing and no correlations with the magnitude of variability quenching in individual participants. An alternative mechanism that may generate variability quenching is increased phase alignment across trials. Moreover, individual magnitudes of alpha-beta band-power explained 86% of between-subject differences in variability quenching. Neural variability quenching was eliminated by excluding the alpha-beta band from the recordings, but not by excluding other frequency-bands. The timing, amplitude, and spatial topography of variability-quenching and power-suppression were remarkably similar. To test this, we examined magnetoencephalography (MEG) recordings of healthy subjects viewing repeated presentations of a visual stimulus. We hypothesized that the two phenomena are tightly coupled in electrophysiological recordings of large cortical neural populations. Despite their similarity, these phenomena have so far been studied and discussed independently. Likewise, the power of neural oscillations, primarily in the alpha-beta band, is also reduced after stimulus onset. This trial-by-trial neural variability is dramatically reduced (“quenched”) after the presentation of sensory stimuli. Neural activity fluctuates over time, creating considerable variability across trials.
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