Customizable optode attachments to improve hair clearance timing and inclusiveness in functional near-infrared spectroscopy research.

Significance: Functional near-infrared spectroscopy (fNIRS) is a promising alternative to functional magnetic resonance imaging for measuring brain activity, but the presence of hair reduces data quality. Aim: To improve research efficiency and promote wider subject inclusivity, we developed the "Mini Comb"-an attachment for commercial fNIRS head caps that can rapidly clear hair with a simple twisting motion. Approach: To test the utility of the Mini Comb on different hair types, we measured the clearance achieved with eight unique sliding leg extrusions on 10 wigged mannequins of various hair characteristics. Following mannequin testing, we recruited a total of 15 participants to evaluate the performance of the Mini Comb as pertains to the time needed to create clearance and the signal quality captured. Results: The Mini Comb achieves comparable signal-to-noise ratios (SNRs) as standard hair clearance procedures while reducing hair clearance time by nearly 50%. Importantly, group analysis revealed better SNR results when the Mini Comb sliding leg design is matched to hair type, suggesting that consideration of hair type is important when conducting fNIRS studies. Conclusions: The Mini Comb thus opens the door for the deployment of fNIRS for more widespread, inclusive, and comprehensive neuroimaging studies.