An errant enzyme linked to bipolar disorder, in the brain’s prefrontal cortex, impairs cognition under stress, an animal study shows. The disturbed thinking, impaired judgment, impulsivity, and distractibility seen in mania, a destructive phase of bipolar disorder, may be traceable to overactivity of protein kinase C (PKC), suggests the study, funded by the National Institutes of Health’s (NIH) National Institute of Mental Health (NIMH) and National Institute on Aging (NIA), and the Stanley Foundation. It explains how even mild stress can worsen cognitive symptoms, as occurs in bipolar disorder, which affects 2 million Americans.