The effects of aging on visual memory: evidence for functional reorganization of cortical networks

Recent evidence suggests that the mature human brain is capable of substant ial functional reorganization following injury. The fact that the brain ret ains a great deal of plasticity raises the possibility that cortical reorga nization may occur during normal aging. We examined this issue by using pos itron emission tomography (PET) to measure the brain activity associated wi th short-term memory for simple visual attributes in young and old observer s. A two-interval forced choice procedure was used to measure spatial frequ ency discrimination thresholds for sine wave gratings presented at differen t inter-stimulus intervals (ISI). Memory load was manipulated by varying th e duration of the ISI and by presenting an irrelevant masking stimulus in t he middle of the ISI, Old and young observers performed the experiment equa lly well. However, the neural systems correlated with good performance diff ered for the two age groups. The results support the hypothesis that the fu nctional networks that underlie visual memory undergo reorganization during aging. (C) 2001 Published by Elsevier Science B.V.