Increased response-time variability is associated with reduced inferior parietal activation during episodic recognition in aging.

Intraindividual variability (IIV) in cognitive performance shares systematic associations with aging-related processes, brain injury, and neurodegenerative pathology. However, little research has examined the neural underpinnings of IIV, with no studies investigating brain correlates of IIV in relation to retrieval success. Using functional magnetic resonance imaging, we examined links between IIV, recognition memory performance, and blood oxygenation level dependent activations. Nineteen older adults (70-79 years) were presented with 80 words at encoding, with brain scans and response latencies obtained during subsequent recognition. An index of IIV, the intraindividual standard deviation (ISD), was computed across successful latency trials. Decreasing ISDs were systematically associated with better recognition, faster latencies, and increased activation in the inferior parietal cortex (BA 40). Demonstrated links between less behavioral variability and parietal activations are consistent with the known importance of the parietal cortex for retrieval success. In support of extant findings and theory from neuroscience, neuropsychology, and cognitive aging, the present results suggest that behavioral IIV represents a proxy for neural integrity.