Neural responses to children’s faces: Test–retest reliability of structural and functional MRI

Introduction: Functional MRI (fMRI) is commonly used to investigate the neural mechanisms underlying psychological processes and behavioral responses. However, to draw well-founded conclusions from fMRI studies, more research on the reliability of fMRI is needed. Methods: We invited a sample of 41 female students to participate in two identical fMRI sessions, separated by 5 weeks on average. To investigate the potential effect of left-handedness on the stability of neural activity, we oversampled left-handed participants (N = 20). Inside the scanner, we presented photographs of familiar and unfamiliar children's faces preceded by neutral and threatening primes to the participants. We calculated intraclass correlations (ICCs) to investigate the test–retest reliability of peak activity in areas that showed significant activity during the first session (primary visual cortex, fusiform face area, inferior frontal gyrus, and superior temporal gyrus). In addition, we examined how many trials were needed to reliably measure the effects. Results: Across all participants, only fusiform face area activity in response to faces showed good test–retest reliability (ICC = 0.71). All other test–retest reliabilities were low (0.01 ≤ ICC ≤ 0.35). Reliabilities varied only slightly with increasing numbers of trials, with no consistent increase in ICCs. Test–retest reliabilities for left-handed participants (0.28 ≤ ICC ≤0.66) were generally somewhat higher than for right-handed participants (−0.13 ≤ ICC ≤0.75), but not statistically significant. Conclusion: Our study shows good test–retest reliability for fusiform facer area activity in response to faces, but low test–retest reliability for other contrasts and areas.