ATXN1 and spinocerebellar ataxia type 1: In order to gain insight into the etiology of SCA1 mood alterations, we systematically (e.g. using the same tests on the same genetic background at 8 weeks of age) investigated how mood in mice was affected by global or cerebellum-limited expression of mutant ATXN1, polyQ length of ATXN1, and loss of ATXN1.