Altered brain response to verbal learning following sleep deprivation

The effects of sleep deprivation on the neural substrates of cognition are poorly understood. Here we used functional magnetic resonance imaging to me asure the effects of 35 hours of sleep deprivation on cerebral activation d uring verbal learning in normal young volunteers. On the basis of a previou s hypothesis', we predicted that the prefrontal cortex (PFC) would be less responsive to cognitive demands following sleep deprivation. Contrary to ou r expectations, however, the PFC was more responsive after one night of sle ep deprivation than after normal sleep. Increased subjective sleepiness in sleep-deprived subjects correlated significantly with activation of the PFC . The temporal lobe was activated after normal sleep but not after sleep de privation; in contrast, the parietal lobes were not activated after normal sleep but were activated after sleep deprivation. Although sleep deprivatio n significantly impaired free recall compared with the rested state, better free recall in sleep-deprived subjects was associated with greater parieta l lobe activation, These findings show that there are dynamic, compensatory changes in cerebral activation during verbal learning after sleep deprivat ion and implicate the PFC and parietal lobes in this compensation.