According to Nora D. Volkow, who gave a talk at Radcliffe’s Knafel Center Thursday titled “The Sleep-Deprived Human Brain,” a single sleepless night is probably harmless, but the cumulative effects of sleep deprivation may be more dangerous than is currently understood, reports The Harvard Gazette.

Volkow, now the director of the National Institute on Drug Abuse at the National Institutes of Health, was a pioneer in positron emission tomography (PET) brain imaging, and helped carry out early studies confirming the toxic effects of cocaine. At Harvard, she reported on two sets of brain-imaging studies that shed light on the way sleep deprivation interferes with cognition, as well as its possible links to dementia and Alzheimer’s disease.

Her work in drug research, she said, led to an investigation of sleep patterns. One toxic property of cocaine is that it interferes with sleep.