Whisking Behaviour Reveals Stronger Evidence of Habituation in Homozygous Reeler Mice Compared to Controls

Abstract

Reeler mice have a mutation in the reelin gene. As a result, Reeler mice lack cortical layers, yet their brains are still largely functional. However, Reeler mice display strong motor phenotypes, including ataxic gait and tics, and we posit that their whisking behaviour might also be disrupted. We used high-speed video to film and track whisker movements in 9 adult Reeler mice and 9 age-matched controls in three whisker movement assessment tasks, including our established novel object exploration and open field tasks, as well as a new open field habituation task. Overall, whisker movements in Reeler mice were highly conserved during the novel object exploration and open field tasks, and they demonstrated all behaviourally relevant whisking features during exploratory contact with an object, including contact-induced asymmetry, spread reduction, and decreasing whisker speeds following object contact. In the habituation task, whisker angular position and whisker spread decreased between the first consecutive sessions in all mice, suggesting that the animals were less focused on sampling the area as they got more familiar with the environment. However, only Reeler mice were affected by more extensive habituation. We suggest that whisker-dependent sensory function is surprisingly intact in Reeler mice. However, our observed habituation-related changes in Reeler mice whisker movements suggest some behavioural differences in these mice, which is a likely result of their disorganised cortex due to reelin deficiency.