Sections were processed for histochemistry, including Nissl staining and cytochrome oxidase staining (23 (link)), and immunohistochemistry as described previously (16 (link), 44 (link)–46 (link, link)). We visualized perineuronal nets using biotinylated Wisteria Floribunda Lectin (Vector; 1:1,000). First, we incubated sections in blocking buffer consisting of 0.1 M PBS and 5% BSA for 1 h at room temperature. Subsequently, free-floating sections were incubated at least overnight with the primary antibodies in 0.1 M PBS containing 1% BSA and 0.5% Triton-X (PBS-X). We used primary antibodies against PV (Swant; 1:5,000), Forkhead box protein P2 (Sigma; 1:500), NeuN (Servicebio; 1:1,000), and Purkinje cell protein 4 (Sigma; 1:500) (for details, see SI Appendix, Table S3). Next, sections were visualized with fluorescent secondary antibodies diluted in PBS-X and then mounted on gelatinized slides. All histological processing was performed with the experimenter being blind to whether the sections were from a shrew from the summer or winter group.