During the torpor state characterized by hypothermia and suspension of energy-consuming cellular processes, various brain regions in animals such as bears, squirrels, and hamsters show a transient, reversable hyperphosphorylation of tau (quantified with CP13 and PHF-1) that are associated with altered synaptic activity and cognitive impairment reminiscent of delirium (Stieler et al. 2011a; Arendt et al. 2003). Here, PHF1 is linked to Cognitive impairment.