The behavior of most animals is extremely complex. Despite accumulating knowledge about the mechanisms of neurons and nervous systems, which regulate these complex behaviors, we have little understanding about how these mechanisms function. In the present study, we analyzed the exploratory behavior of mice repeatedly exposed to a novel context and tracked the changes in the fluctuation patterns of the accumulated level of body movement suppression (BMS). As a result, we found that the fluctuation in BMS can be divided into two phases, which show a pattern of progressive transition from the initial state to the context-dependent and stable equilibrium state. In the former, transition phase, the level of BMS was easily affected by the number of exposures and mental status of mice. However, in the latter, equilibrium phase, the level of BMS was only dependent on the environmental stimuli involved in the context. On the basis of the results, we suggests here a model that explains the determination of complex behavior observed in higher animals by means of the probability of behavioral expression.

Keywords: body movement suppression, behavioral state, transition phase, equilibrium phase, probability of behavioral expression