Demands on perceptual and mnemonic fidelity are a key determinant of age-related cognitive decline throughout the lifespan
Gellersen, H.M., McMaster, J.M.V., Abdurahman, A., & Simons, J.S. (2024). Journal of Experimental Psychology: General, 153, 200-223.
Ageing results in less detailed memories, reflecting reduced fidelity of remembered compared to real-world representations. We tested whether poorer representational fidelity across perception, short-term and long-term memory (STM/LTM) are among the earliest signs of cognitive ageing. Our paradigm probed target-lure object mnemonic discrimination and precision of object-location binding. Across the lifespan, cognitive deficits were observed in midlife when detailed stimulus representations were required for perceptual and short/long-term Forced Choice mnemonic discrimination. A continuous metric of objectlocation source memory combined with computational modelling demonstrated that errors in short- and long-term memory in middle-aged adults were largely driven by a loss of precision for retrieved memories, not necessarily by forgetting. On a trial-by-trial basis, fidelity of item and spatial information was more tightly bound in long- compared to short-term memory with this association being unaffected by age. Standard neuropsychological tests without demands on memory quality (digit span, verbal learning) were less sensitive to age effects than short-and long-term memory precision. Perceptual discrimination predicted mnemonic discrimination. Neuropsychological proxies for prefrontal executive functions correlated with short-term, but not long-term, memory fidelity. Conversely, neuropsychological indicators of hippocampal integrity correlated with mnemonic discrimination and precision of both STM and LTM, suggesting partially dissociable mechanisms of inter-individual variability in shortand long-term memory fidelity. These findings suggest that reduced representational fidelity is a hallmark of cognitive ageing across perception, short-term and long-term memory and can be observed from midlife onwards. Continuous memory precision tasks may be promising for the early detection of subtle age-related cognitive decline.