Sex-differences in resting state dorsolateral prefrontal cortex: comparing motion correction methods in resting state functional near-infrared spectroscopy (fNIRS).

Functional near-infrared spectroscopy (fNIRS) is a low cost, non-invasive alternative for studies comparing task-based activity of prefrontal cortex regions for cognitive studies with clinical relevance. However, motion correction algorithms are a major source of methodological variability in fNIRS studies, obscuring neurobiological variability in prefrontal hemodynamic response and leading to irreproducible findings. Further, motion correction fNIRS studies disregard sex-differences in hemodynamic response at resting state dorsolateral prefrontal cortex, especially fewer studies are carried out in non-western population. Although resting state brain activity is used for comparing task-based hemodynamics changes especially in tasks that show consistent sex differences (working memory & decision-making tasks) and are associated with affective disorders. Hence, we examined sex-differences in signal variability across eight motion correction approaches and HbO-HbR correlation in fNIRS data of resting state dorsolateral prefrontal cortex (DLPFC). Next, we investigated how right-lateralized resting state DLPFC activity relates with sex-differences in depression-anxiety scores. Resting-state fNIRS data were acquired from 99 healthy adults (47 males, Mean age: 19.75 ± 1.27) Depression-anxiety comorbidity was assessed using Beck Depression Inventory-II (BDI-II) and Beck Anxiety Inventory (BAI) scores. Raw fNIRs signals were processed through eight motion correction pipelines for comparing No Correction, PCA, tPCA, Spline, SplineSG, Wavelet, Hybrid (SplineSG + Wavelet), and TDDR. These were evaluated on peak/minima amplitudes (ΔHbO, ΔHbR, ΔHbT, ΔHbD), HbO-HbR correlation, and signal variability. Hybrid and TDDR motion correction methods yielded the strongest negative HbO-HbR correlation, and lowest signal variability. Independent of motion correction methods, women exhibited stronger HbO-HbR correlation and lower ΔHbO variability, while men showed higher ΔHbT peaks and ΔHbR minima. Sex differences in right-lateralized hemodynamic activity in resting state DLPFC was observed in the form of interaction of sex, depression-anxiety comorbidity and ΔHbD peaks put through motion correction methods. Results indicate that choice of motion correction algorithm might impact our understanding of sex-differences in hemodynamic activity in dorsolateral prefrontal cortex. Sex-differences in affective disposition might be evident even in resting state right-lateralized activity in DLPFC.