The Effects of Age on the Relationship between Memory Performance and Brain Activation during Encoding and Retrieval.

Abstract:
Recent neuroimaging studies of episodic memory reveal that older adults brain activity is reduced in regions recruited by younger adults, but increased in regions not recruited by younger adults. Although these results provide clues regarding the neural mechanisms of memory decrements, they do not directly address age-related differences in patterns of brain activity that facilitate or hinder memory performance. Using PET, we scanned during the encoding and retrieval of word pairs, and investigated the relationship between brain activity and behavior using partial least squares. The pattern of brain activity that facilitated younger adults memory included left prefrontal regions during encoding and right prefrontal regions during retrieval. The pattern of brain activity that facilitated older adults memory included medial frontal and cingulate regions during encoding, and no right prefrontal regions during retrieval. In addition, left hippocampal activation impaired older adults memory, but was moderately beneficial to younger adults memory. Given these data and the fact that older adults recalled fewer words than younger adults, we conclude that older adults use less effective memory strategies that are mediated by different functional networks. Previous evidence that the attentional demands of memory increase with age (Anderson et al., 1998) may be linked to older adults greater reliance on medial frontal/cingulate regions to support memory performance.