Contrary to popular belief, rats and mice are very fastidious animals; they keep themselves scrupulously clean by engaging in a very meticulous routine of self-grooming. The routine is so rigorous that allows the researchers to divide the grooming sequence into four different phases, starting with the nose and whiskers and ending with the genitalia and tail. It is also a symmetrical behavior (no whisker left ungroomed, no paw unlicked).
Grooming is sensitive to dopaminergic manipulations, so Pelosi, Girault, & Hervé (2015) sought to see what happens if they destroy the dopamine fibers in the mouse brain. So they lesioned the medial forebrain bundle, which is a bunch axon fibers that contains over 80% of the midbrain dopaminergic axons. But they were tricky, they lesioned only one side.
And the results were that the lesioned mice not only exhibited less self-grooming on the opposite side to the lesion, but the behavior was rescued by L-DOPA, which is medication for Parkinson’s. That is, they gave the mice some L-DOPA and they began to merrily self-groom again on both sides of the body. The authors discuss in depths other findings, like the changes (or absence thereof) in grooming bouts, grooming time, grooming bouts, completeness of grooming etc.
The findings have significance in the Parkinson’s research, where the mild to moderate phases of the disease often present with asymmetrical motor behavior.
Reference: Pelosi A, Girault J-A, & Hervé D (23 Sept 2015). Unilateral Lesion of Dopamine Neurons Induces Grooming Asymmetry in the Mouse. PLoS One. 2015; 10(9): e0137185. doi: 10.1371/journal.pone.0137185. PMCID: PMC4580614. Article | FREE FULLTEXT PDF
By Neuronicus, 29 October 2015