Influence of study design on effects of mask wearing on fMRI BOLD contrast and systemic physiology — A comment on Law et al. (2021)
F. Scholkmann,
J.B. Fischer,
L. Kobayashi Frisk,
R. Delgado-Mederos,
M. Mayos,
D. Highton,
U. Wolf,
M. Wolf,
T. Durduran
Affiliations
F. Scholkmann
University Hospital Zurich, University of Zurich, Department of Neonatology, Biomedical Optics Research Laboratory, Zurich, Switzerland; Institute of Complementary and Integrative Medicine, University of Bern, Bern, Switzerland; Corresponding auhor.
J.B. Fischer
ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain
L. Kobayashi Frisk
ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain
R. Delgado-Mederos
Hospital de la Santa Creu i Sant Pau, Department of Neurology, Sant Pau Biomedical Research Institute, Barcelona, Spain
M. Mayos
Hospital de la Santa Creu i Sant Pau, Department of Respiratory Medicine, Sleep Unit, Barcelona, Spain; CIBER Enfermedades Respiratorias (CibeRes) (CB06/06), Madrid, Spain
D. Highton
Princess Alexandra Hospital, University of Queensland, Woolloongabba, Australia
U. Wolf
Institute of Complementary and Integrative Medicine, University of Bern, Bern, Switzerland
M. Wolf
University Hospital Zurich, University of Zurich, Department of Neonatology, Biomedical Optics Research Laboratory, Zurich, Switzerland
T. Durduran
ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
In a study by Law and colleagues recently published in Neuroimage, the authors reported that wearing a surgical mask during an fMRI scan leads to a statistically significant subject-specific change (30%) in the baseline BOLD level in gray matter, although the response to a sensory-motor task was unaffected. An average increase in end-tidal CO2 of 7.4% was found when wearing a mask, despite little support in the literature for major effects of mask wearing on blood gas levels. We comment on these findings, point out a several relevant limitations of the study design and provide alternative interpretations of these data.
