Neural correlates mediating age differences in episodic memories: Evidence from bold contrasts and connectivity analyses

Recent advances in fMRI methodology have allowed researchers to examine agerelated neural differences underlying episodic memory from both a quantitative and network level approach. Specifically, BOLD (blood-oxygen-level- dependent) contrasts have observed age-related decreases and increases in overall neural activation. Regarding increases, the pattern of activity often results in more bilateral frontal activation (described as Hemispheric Asymmetry Reduction in OLDer adults; HAROLD) or greater recruitment of frontal regions (described as Posterior to Anterior Shift in Aging; PASA) in aging. These increases are largely interpreted as compensatory and beneficial to memory performance. Similar to BOLD findings, connectivity analyses showed age-related plasticity within the episodic memory network, with results converging on a similar posterior-to-anterior shift in the coherence of regions associated with medial temporal lobe activity during episodic encoding and retrieval. This paper reviews the latest neuroimaging findings across both BOLD and connectivity results associated with age-related differences in episodic memory.