Beyond Synchrony: Non-Phase Gamma as a Candidate Mechanism for Perceptual Anti-Binding

The gamma band observed in human electroencephalography (EEG) has been extensively studied. However, recent research has begun distinguishing the potential roles assigned to phase and non-phase modulation within this band. The primary aim of this study is to analyze the potential role of non-phase gamma modulation in a widely used visual task in human subjects. For this purpose, using a 58-channel EEG recording, gamma activity was evaluated during an oddball task. Responses from 21 healthy subjects were recorded at two separate time points, with an average interval of 49.5 ± 48.9 days. Latency, amplitude, and topographic correlation values were calculated to assess the replicability. Furthermore, potential influence of alpha band harmonics on gamma was analyzed. Topographic analyses revealed a strong negative correlation between gamma phase-locked (synchronous) and non-phase-locked (asynchronous) activity, with correlation coefficients of r < −0.9 for both measures. The results observed between the two time points were robust. The harmonic analysis did not show any potential contribution of the alpha band. The separate analysis of phase and non-phase activity has enabled us to identify distinct roles for each. Establishing non-phase activity as a perceptual “anti-binding” mechanism opens new avenues for exploring a previously unaddressed aspect of gamma activity.