Repetition-related reductions in neural activity support improved behavior through increases in oscillatory power

Repeatedly processing an object leads to subsequent behavioral improvements in its identification and reductions in associated neural activity, a form of neural processing efficiency that multiple theoretical models have attempted to explain. Using simultaneous EEG/fMRI in humans during object naming, we find that stimulus-driven oscillatory power from high (gamma) to low frequencies (theta) increases and resolves earlier with repetition in task-engaged frontal and occipitotemporal brain regions identified as showing repetition suppression in fMRI. Repetition-related increases and decreases in gamma oscillatory power in these regions were correlated with behavioral priming across subjects (|rs| ≥ 0.39) and additionally with fMRI repetition suppression in left frontal cortex (r = -0.37). Similar correlations were observed between behavioral priming and oscillatory power changes when effects were examined within subjects (|rs| ≥ 0.34). Collectively, these data provide multimodal support for a novel mixture of the previously proposed Synchrony and Facilitation models.