Tracking Insulin to the Mind

CELLULAR NEUROSCIENCEAlthough insulin is not supposed to play a role in the brain, recent evidence in both lab animals and humans suggests that the hormone may be needed for normal brain functions, including learning and memory; if so, defects in the brain's ability to use insulin could lead to anything from mild memory loss to Alzheimer's disease. The idea is still controversial, however, partly because no one yet knows exactly how insulin might affect brain neurons. Some researchers suggest that the hormone chaperones glucose to brain neurons and thereby helps them maintain their energy production, in which case, memory loss might result when brain cells lack insulin and become glucose starved. Others hypothesize that insulin has other beneficial roles, such as spurring neuronal growth and inhibiting the formation of brain lesions called neurofibrillary tangles that characterize Alzheimer's. If insulin's role in cognition can be pinned down, though, the work might one day point the way to drugs that could reduce memory loss in both Alzheimer's and normal aging.