Tip-of-the-tongue States in Aging: Evidence From Behavioral and Neuroimaging Studies

Abstract

Metamemory is defined as the knowledge about one's memory capabilities and about strategies that can aid memory (Shimamura, 1994). One particularly intriguing type of metamemory judgment is a tip-of-the-tongue experience, which refers to a strong feeling that a target word, though presently not recalled, is known and on the verge of being produced. Older adults report more TOT experiences than young adults. However, there is great variability among older adults in performance on memory and executive function tasks, and it is unknown whether subsets of older adults experience more TOT states. Additionally, the neural correlates of successful retrieval, TOTs, and unsuccessful retrieval in aging have not been studied. In the studies reported here, the relationship between frontal and medial temporal neuropsychological factor scores (see Glisky et al., 1995) and performance on metamemory tasks was examined. Importantly, this was the first study to examine the neural correlates of tip-of-the-tongue experiences in older adults. In an event-related fMRI design, participants viewed famous and novel faces and were asked to respond regarding successful retrieval, unsuccessful retrieval, or tip-of-the-tongue experiences. Results show that, as a group, older adults had activation in the medial prefrontal cortex and anterior cingulate during tip-of-the-tongue states, consistent with similar studies in young adults (Maril et al., 2001; Pannu et al., 2004, Schnyer et al., 2005). Additionally, activations in lateral prefrontal cortex and medial temporal areas during the task varied systematically with frontal and temporal lobe factor scores. These results provide evidence for differences in neural activation between groups of healthy older adults characterized on the basis of neuropsychological performance, and shed light on the neural underpinnings of the tip-of-the-tongue states in aging.