Whisker exploration behaviours in the 5xFAD mouse are affected by sex and retinal degeneration.

Active whisking in mice and rats is one of the fastest behaviours known in mammals and is used to guide complex behaviours such as exploration and navigation. During object contact, whisker movements are actively controlled and undergo robust changes in timing, speed and position. This study quantifies whisker movements in 6- to 7-month old male and female 5xFAD mice, and their C57/SJL F1 wild-type (WT) controls. As well as genotype, we examined sex differences and the effects of retinal degeneration (rd). Mice were filmed using a high-speed video camera at 500 frames per second (fps), under infrared light while behaving freely in three tasks: object exploration, sequential object exploration and tunnel running. Measures of whisker position, amplitude, speed and asymmetry were extracted and analysed for each task. The 5xFAD mice had significantly altered whisker angular positions, amplitude and asymmetry during object contacts and female 5xFAD mice with rd had lower mean angular positions during object contact. There were no significant effects of genotype on sequential object exploration or on tunnel running but differences due to sex and rd were found in both tasks, with female mice making larger and faster whisker movements overall, and mice with rd making larger and faster whisker movements during object contact. There were sex differences in whisker movements during sequential object exploration and females with rd had higher whisker retraction speeds in tunnel running. These data show that measuring whisker movements can quantify genotype and sex differences and the effects of rd during exploratory behaviour in these mice.