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.