Abstract
Background
The CST is a novel assessment that was designed to measure cognitive changes during preclinical and prodromal stages of AD, that include aMCI and PreMCI, where deficits do not meet MCI. The CST employs semantically competing word lists to measure the impact of semantic interference, failure to recover from proactive semantic interference (frPSI), and its persistent effects, despite multiple trials. We hypothesized that frPSI deficits on the CST would be persistent in pre‐MCI and aMCI groups when compared to cognitively unimpaired (CU) controls.
Method
50 aMCI, 31 pre‐MCI, and 69 CU elders were administered the CST. Participants were presented with List A (18 semantically related words: occupations, household items, or transportation methods) for three initial learning trials, followed by three learning trials of List B, a categorically similar wordlist, to examine PSI and frPSI. Retroactive Semantic Interference (RSI) was assessed by using category cues to elicit recall of List A targets, followed by an additional learning trial to examine failure to recover from RSI (frRSI).
Result
Significant differences were observed between all diagnostic groups across CST Cued Recall trials that measure maximum learning, PSI, frPSI, and persistent frPSI. PreMCI and aMCI participants experienced deficits in learning List B despite two additional opportunities; a deficit that was observed even after adjusting for initial learning strength. Older adults with greater risk (preMCI and aMCI) performed similarly on indices that measures PSI, frPSI, and persistent frPSI as compared to controls. There were differences in RSI among CU and aMCI groups yet measuring frRSI did not differentiate groups. aMCI participants made more semantic intrusion errors on recall trials that cued List B words. Pre‐MCI and CU made a similar number of intrusion errors.
Conclusion
The CST extends our work by assessing persistent effects of frPSI, which have been shown to predict neurodegenerative progression and have been associated with multiple biomarkers of AD. The finding that persistent frPSI could differentiate CU from preMCI groups is a promising indicator that semantic interference deficits persist in older adults that present a heightened risk for progression to dementia and is worthy of further research.