Intraindividual variability in performance on associative memory tasks is elevated in amnestic mild cognitive impairment

Elevations in intraindividual variability (IIV) are an indicator of neurocognitive compromise and are seen on reaction time tasks in individuals with mild cognitive impairment (MCI). We examined IIV on memory tasks known to be sensitive to early cognitive change in a group of 24 individuals with amnestic MCI and 21 matched controls. Traditional measures of accuracy and speed, as well as indices of IIV statistically purified for systematic between-group and trial effects, were derived from performance on two computer-based associative recognition tests of word-word and face-name pairs. Accuracy and speed were reduced and IIV was elevated in the MCI group compared to controls on both tasks. Logistic regression analyses demonstrated that IIV, but not speed, was a unique predictor of group membership, over and above performance accuracy. Observed elevations in IIV in MCI are congruent with the notion that IIV may reflect disturbance in distributed neural networks, including medial temporal regions, in addition to frontal systems dysfunction. Present findings have diagnostic implications for accurate identification of individuals with MCI and add to the growing literature on IIV as an early indicator of cognitive decline in older adults.