Sex differences in head-fixed voluntary running behavior in C57BL/6J mice.

Sex differences in running behaviors between female and male mice occur naturally in the wild. Recent experiments using head-fixed mice on a voluntary running wheel have exploited analogous locomotor activity to gain insight into the neural underpinnings of a number of behaviors ranging from spatial navigation to decision-making. It is however largely unknown if sex differences exist between females and males in a head-fixed experimental paradigm. To address this, we characterized locomotor activity in head-fixed female and male C57BL/6J mice on a voluntary running wheel. First, we found that over the initial 7-day period, on average, animals increased both the velocity and the time spent running. Furthermore, we found that female mice habituated to running forward over the initial 2 days of encountering the wheel, while male mice took up to 4 days to habituate to running forward. Taken together, we characterized features of a sexually divergent behavior in head-fixed running that should be considered in experiments employing female and male mice.