Representative in situ hybridizations for per1 expression in two horizontal brain sections from a sleep deprived (SD, lower panels) and a control (upper panels) mouse. Following 6 h SD per1 mRNA increased throughout the brain. This increase was especially pronounced in the cerebral cortex and cerebellum (CB), consistent with our qPCR data (Fig. 1). Note the very low cortical expression in control mice which, at ZT6, spent most of the preceding 6 h sleeping. Within the cortex, increases were especially notable in the frontal cortex (FC) and in and around the cingulate cortex. Caudate-Putamen (CP) and hippocampus (HP) are labeled for orientation.