TY - JOUR T1 - The Medial Frontal Cortex Generates Rhythmic Activity that Encodes Reward Value JF - bioRxiv DO - 10.1101/144550 SP - 144550 AU - Linda M. Amarante AU - Marcelo A. Caetano AU - Mark Laubach Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/07/11/144550.abstract N2 - Rodents lick to consume fluids. The reward value of ingested fluids is likely to be encoded by neuronal activity entrained to the lick cycle. Here, we investigated relationships between licking and reward signaling by the medial frontal cortex [MFC], a key cortical region for reward-guided learning and decision-making. Multi-electrode recordings of spike activity and field potentials were made in male rats as they performed an incentive contrast licking task. The rats received access to higher and lower value sucrose rewards over alternating 30 sec periods. They learned to lick persistently when the higher value reward was available and to suppress licking when the lower value reward was available. Spectral analysis of spikes and fields revealed evidence for reward value being encoded by the strength of phase locking of 4-12 Hz rhythmic activity to the rats’ lick cycle. Recordings during the initial acquisition of the task found that the strength of phase locking to the lick cycle was strengthened with experience. A modification of the task, with a temporal gap of 2 sec added between reward deliveries, showed that the rhythmic signals persisted during periods of dry licking, a finding that suggests the MFC encodes the value of the currently available reward. Finally, we found that reversible inactivations of the MFC in the opposite hemisphere eliminated the encoding of reward information. Together, our findings establish that 4-12 Hz rhythmic activity is generated by neurons in the MFC to encode the value of consumed rewards.Significance Statement The cellular and behavioral mechanisms of reward signaling by the medial frontal cortex [MFC] have not been resolved. We report evidence for a dynamic encoding of reward value by neuronal activity in the MFC that is synchronized with ongoing consummatory actions. Previous studies of MFC reward signaling have inferred value coding upon temporally sustained activity during the period of reward consumption. Our findings suggest that MFC activity is temporally sustained due to the consumption of the rewarding fluids, and not necessarily the abstract properties of the rewarding fluid. Two other major findings were that the MFC reward signals persist beyond the period of fluid delivery and are generated by neurons within the MFC. ER -