Reproducible between-person brain-behavior associations do not always require thousands of individuals

Abstract

Marek et al. analyzed three very large magnetic resonance imaging (MRI) datasets and concluded that thousands of participants are necessary to ensure replicable results in “brain-wide associations studies,” which they defined as “studies of the associations between common inter-individual variability in human brain structure/function and cognition or psychiatric symptomatology.” This conclusion overgeneralizes the implications of their findings and is likely to have an unwarranted chilling effect on neuroimaging research focused on individual differences, preventing good research with samples in the hundreds from being funded and conducted. To fend off these negative consequences, we explain why their conclusion is not fully justified, discuss methods that can yield larger effects, and suggest practical guidelines for sample size, recognizing the potential utility of samples in the hundreds.

Conduction velocity along a key white matter tract is associated with autobiographical memory recall ability

“…Specifically, the sample allowed for sufficient power to identify medium effect sizes when conducting correlation analyses at alpha levels of 0.01 and when comparing correlations at alpha levels of 0.05 ( Cohen, 1992 ). Samples of over 200 participants have also been suggested as sufficient for correlational neuroimaging research similar to that performed here ( Cecchetti and Handjaras, 2022 ; DeYoung et al, 2022 ).…”

“…Our analyses were also performed using weighted means from each of the three white matter tracts of interest rather than voxel-wise across the whole brain, reducing the potential for false positives ( Marek et al, 2022 ). We also tested a sample of over 200 participants, which has been suggested as sufficient for correlational neuroimaging research such as that performed here ( Cecchetti and Handjaras, 2022 ; DeYoung et al, 2022 ). Relationships with autobiographical memory recall ability were also specific to the MR g-ratio, and were not evident for any of its components (magnetisation transfer saturation, neurite density or isotropic volume fraction), suggesting that it is the combination of these measures, in the form of the MR g-ratio, that is meaningful rather than any single measure alone.…”

Conduction velocity along a key white matter tract is associated with autobiographical memory recall ability

“…Specifically, the sample allowed for sufficient power to identify medium effect sizes when conducting correlation analyses at alpha levels of 0.01 and when comparing correlations at alpha levels of 0.05 (Cohen, 1992). Samples of over 200 participants have also been suggested as sufficient for correlational neuroimaging research similar to that performed here (Cecchetti and Handjaras, pre print; DeYoung et al, pre print).…”

“…Our analyses were also performed using weighted means from each of the three white matter tracts of interest rather than voxel-wise across the whole brain, reducing the potential for false positives (Marek et al, 2022). We also tested a sample of over 200 participants, which has been suggested as sufficient for correlational neuroimaging research such as that performed here (Cecchetti and Handjaras, pre print; DeYoung et al, pre print).…”

Dissociation of reliability, heritability, and predictivity in coarse- and fine-scale functional connectomes during development

“…However, leveraging machine learning advances including multivariate models, functional alignment, or individual-specific functional atlases as opposed to group-average atlases is one approach to improving prediction 12,15,54,55,34,35,56 . Our study demonstrates the power of hyperalignment as a tool for understanding developing individual differences in brain and behavior.…”