A critical aspect of recognition memory is the integration of available memory evidence and a decision criterion. Episodic retrieval and criterion shifting involve distinct brain regions that are engaged differentially across individuals depending on unique characteristics and strategies. In this study we attempted to quantify how aging interacts with such factors in their influence on criterion placement during recognition memory. Recognition memory and criterion shifting behavior and brain activity were examined in late adolescents (age 18), young (ages 25-33) and older (ages 60-75) adults during an fMRI task. We also assessed individuals on over 100 variables that may mediate one's willingness and ability to shift decision criterion. On average, discriminability, criterion placement, and shifting for high- and low-target probability conditions were similar across groups. Of particular interest is our criterion shifting results, given mixed findings across other studies. It appears that when predictable shifts are required and when changes in demands are clear and unambiguous, as is the case with our design, older adults have the cognitive capacity to adapt in a more optimal manner. Furthermore, we found large variability in the degree to which individuals shift their decision criterion between conditions. Using a hierarchical regression approach, we identified a group of key variables that accounted for over 30% of the variance in criterion shifting. After controlling for these variables, age did not emerge as having any additional explanatory power of that variance, suggesting that differences in inherent characteristics are more important in explaining the variability in criterion shifting than age alone.

As individuals age, the brain undergoes considerable structural and functional changes which mediate the decline of higher-order cognition. Several studies have demonstrated age-related over-recruitment of brain regions typically involved in retrieval in younger adults, perhaps in an attempt to compensate for other age-related impairments. However, no study has examined criterion-shifting-related activity in young and older adults. Our results showed that both young and older adults activated a number of frontoparietal regions that are a hallmark of successful episodic memory retrieval for both successful retrieval (hits vs. correct rejections) and criterion shifting (switch vs. same trials) contrasts. Whole-brain analyses revealed no evidence of over-recruitment by older adults for either successful retrieval (hits vs. correct rejections) or criterion shifting (switch vs. same trials), although regional analyses revealed that younger adults actually showed greater activity in right parietal regions. Given that no significant positive correlation was found between criterion shifting behavior and activity in these regions, combined with the equivalent criterion shifting behavior observed in our older adults, it appears that right parietal activation is not necessarily beneficial for shifting performance. We further discuss that the lack of over-recruitment by older adults in our study is not usual, particularly when a yes/no recognition memory is utilized and performance is matched. Both our behavioral and performance results suggest that our recognition memory task and its underlying criterion shift manipulation involved a manageable amount of cognitive load resulting in similar performance and brain activation for young and older adults.