Comparison of single- and across-trial fMRI estimates of encoding-related activity in young and older adults

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

Marianne de Chastelaine¹ (mad106120@utdallas.edu), Mingzhu Hou¹, Sarah Monier¹, Michael Rugg¹; ¹UTD

We re-analyzed fMRI associative encoding-related activity acquired from 36 young and 64 older adults, utilizing trial-by-trial estimates of BOLD signal magnitude (beta estimates) to compute participant-wise effect sizes of fMRI ‘subsequent memory effects’ (SMEs) in a range of brain regions. These estimates were compared with those derived from the original analysis of the same data which employed an across-trial estimation procedure. We examined ‘positive’ SMEs in bilateral IFG and left hippocampus, and ‘negative’ SMEs in 9 additional regions. Consistent across estimation methods, IFG SMEs were more left-lateralized in the young compared to the older group and negative SMEs were robust in young participants. However, while the original analyses indicated a positive correlation between right IFG SMEs and memory performance in the older group, SMEs estimated with the single-trial approach demonstrated a negative relationship with memory performance in the same participants. Moreover, hippocampal SMEs were robust across age groups using across-trial estimates, but unreliable in either age group when estimated using the single-trial approach. In the regions where older adults’ negative SMEs were reliable in the original analyses, these effects reversed in direction when estimated using the single trial approach. Unsurprisingly, in light of these findings, across-participant correlations between single- and across-trial SME estimates were low (rs = .04 to .45). Clearly, single-trial and the more conventional across-trial approaches to estimating fMRI contrasts do not necessarily converge. Possible reasons for the divergent results will be discussed.

Topic Area: METHODS: Neuroimaging