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

Abstract

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.

Pinnipeds orient and control their whiskers: a study on Pacific walrus, California sea lion and Harbor seal

“…2b). In rats (Arkley et al 2014) and mice (Grant et al 2018b), blind animals tend to have larger amplitude whisker movements, although we do not observe this in the Harbor seal example. In addition, in our study, one Pacific walrus was blind, and one Harbor seal had cataracts in both eyes, but these individuals did not have significantly different whisker movements or positions compared to other individuals of the same species (Supplementary Material 3).…”

“…The animals were not blindfolded for this study to give ethologically relevant values of whisker movements (in line with the procedures in Milne and Grant 2014), since in the wild whisker movements will never occur in the absence of vision, unless the animal is blind or they are hunting on a particularly dark night or in murky water. Blindfolding the animal may also increase their reliance on whisker touch, causing increases in whisker amplitude that would not be representative of usual whisker movements (Arkley et al 2014;Grant et al 2018b). In addition, these animals were all zoo animals, and not trained for research activities; therefore, blindfolding was considered to expose them to unnecessary suffering and stress.…”

Dissociating the effects of distraction and proactive interference on object memory through tests of novelty preference

“…Whilst the present data agree with prior studies that scPCP rodents have no deficit in acquiring and maintaining object memoryin the absence of distraction, we tested whether there was a quantitative difference in how scPCP rats use their whiskers to sense this information. Whisker movements during object contact are a vital source of environmental information for rodents and these are abnormal in other rodent models of neuropsychiatric disease that express sensory, motor and cognitive deficits (Grant et al, 2014;Grant et al, 2020;Simanaviciute et al, 2018;Garland et al, 2018).…”

“…Here, we first ensured that scPCP treatment had no a priori effect on object sensing through whisker movements. This was important as whisker kinematics provide key tactile information to rodents about the environment and are altered in other rodent disease models (Grant et al, 2020;Grant et al, 2014;Simanaviciute et al, 2018). We next ran stNOR to reproduce the effect of distraction in scPCP rats.…”

Sex differences in mechanisms of disease

“…An extensive battery of locomotor behavior across the adult lifespan (age 3‐16 months) showed that, despite robust motor deficits in 5xFAD mice of both sexes and a few age‐dependent sex differences, very few sex × genotype interactions could be observed . Along similar lines, Grant et al found that whisking behavior in several exploratory tasks depended more on sex and the presence of retinal degeneration than on the 5xFAD genotype itself. Taken together, these studies suggest that this particular mutant may not be ideal for studying the aspects of AD that are sex‐dependent.…”