Good Vibrations: Cross-frequency Coupling in the Human Nucleus Accumbens during Reward Processing

The nucleus accumbens is critical for reward-guided learning and decision-making. It is thought to “gate” the flow of a diverse range of information (e.g., rewarding, aversive, and novel events) from limbic afferents to basal ganglia outputs. Gating and information encoding may be achieved via cross-frequency coupling, in which bursts of high-frequency activity occur preferentially during specific phases of slower oscillations. We examined whether the human nucleus accumbens engages such a mechanism by recording electrophysiological activity directly from the accumbens of human patients undergoing deep brain stimulation surgery. Oscillatory activity in the gamma (40–80 Hz) frequency range was synchronized with the phase of simultaneous alpha (8–12 Hz) waves. Further, losing and winning small amounts of money elicited relatively increased gamma oscillation power prior to and following alpha troughs, respectively. Gamma–alpha synchronization may reflect an electrophysiological gating mechanism in the human nucleus accumbens, and the phase differences in gamma–alpha coupling may reflect a reward information coding scheme similar to phase coding.