Periaqueductal gray passes over disappointment and signals continuity of remaining reward expectancy

Animals navigate environments with multiple objects to find rewards. We previously found that phasic activities of lateral habenula (LHb) neurons encode step-by-step changes in reward predictions induced by the series of multiple objects and errors. However, to obtain the reward, another important source would be to maintain their mind at the beginning and tolerate capricious errors in following steps to continue the sequence of actions. We found that periaqueductal gray (PAG) neurons, LHb downstream brain area, transport reward expectation from one step to the next step, affecting subsequent behaviors. The tonic PAG activities correlated with animal behavior responding to a cue and also contextually affected subsequent behaviors (vigorous reaching and holding). This research suggests that phasic and tonic signaling in the LHb-PAG pathway plays a crucial role in deciding the continuation versus discontinuation of reward-seeking behaviors in the sequential steps and enables animals to search complex environments and find rewards.