Behavioral/Systems/Cognitive Gamma-Phase Shifting in Awake Monkey Visual Cortex

Gamma-bandsynchronization is abundant innervous systems.Typically, the strengthorprecisionof gamma-bandsynchronization is studied. However, the precise phasewithwhich individual neurons are synchronized to the gamma-band rhythmmight have interesting consequences fortheir impactonfurtherprocessingandforspiketiming-dependentplasticity.Therefore,weinvestigatedwhetherthespiketimesof individual neurons shift systematically in the gamma cycle as a function of the neuronal activation strength.We found that stronger neuronal activation leads to spikes earlier in the gammacycle, i.e., we observed gamma-phase shifting. Gamma-phase shifting occurred on very rapid timescales. It was particularly pronounced for periods in which gamma-band synchronization was relatively weak and for neurons that were only weakly coupled to the gammarhythm.Wesuggest that gamma-phase shifting is brought about by an interplaybetweenoverall excitation andgamma-rhythmic synaptic input and has interesting consequences for neuronal coding, competition, and plasticity