AGE-RELATED DIFFERENCES IN EFFECTIVE NEURAL CONNECTIVITY DURING ENCODING AND RECALL

AGE-RELATED differences in brain activity may reflect local neural cha nges in the regions involved or they may reflect a more global transfo rmation of brain function. To investigate this issue, we applied struc tural equation modeling to the results of a positron emission tomograp hy (PET) study in which young and old adults encoded and recalled word pairs. In the young group there was a shift from positive interaction s involving the left pr,frontal cortex during encoding to positive int eractions involving the right prefrontal cortex during recall, whereas in the old group frontal interactions were mixed during enoding and b ilaterally positive during recall. The present results suggest that ag e-related changes in neural activation are partly due to age-related c hanges in effective connectivity in the neural network underlying the task.