Working memory load-related activity in the left middle frontal gyrus (significant cluster from the Load Condition effect during retrieval), measured as the difference in activity between Load 6 and Load 2, is plotted as a function of working memory capacity, measured by WAIS-III Digit Span backward (top) and Cowan’s K (bottom), separately for younger (left) and older (right) adults. Higher working memory capacity was associated with significantly greater load-related activity in younger adults, whereas load-related activity did not vary as a function of working memory capacity for older adults.