Developing Best Practices for Inclusion in fNIRS Research: Equity for Participants with Afro-Textured Hair

Functional near-infrared spectroscopy (fNIRS) is a popular optical neuroimaging method; however, participants with Afro-textured hair (i.e., dark, coarse, curly) are often excluded due to difficulty obtaining sensor-scalp contact. In this mixed-methods study, we developed and evaluated best practices for participant interaction and hair preparation to increase Black inclusion in fNIRS research. First, qualitative interviews with hair professionals informed the development of an intake survey, a suite of customizable hair preparation techniques, and recommendations for researcher staffing and training, while prioritizing participant comfort and hair integrity. We then evaluated these techniques with 16 Black participants (11 adults, 5 children) with varying hair types/styles, including braiding cornrows around the intended optode montage, using gels and clips to part hair, and various ways of increasing tension to promote sensor-scalp contact. On average, signal improved by 44%, with greatest improvements in anterior regions. While signal quality was not perfect, it was generally improved to the point of acceptability and inclusion in a racially and ethnically diverse dataset (with hair type/color as covariates). We conclude by discussing the need for increased awareness of racial bias in neuroimaging, greater diversity in research teams, and a more inclusive approach for working with diverse populations.