Portable Functional Neuroimaging as an Environmental Epidemiology Tool: A How-To Guide for the Use of fNIRS in Field Studies

Abstract

Summary:The widespread application of functional neuroimaging within the field of environmental epidemiology has the potential to greatly enhance our understanding of how environmental toxicants affect brain function. Because many epidemiological studies take place in remote and frequently changing environments, it is necessary that the primary neuroimaging approach adopted by the epidemiology community be robust to many environments, easy to use, and, preferably, mobile. Here, we outline our use of functional near-infrared spectroscopy (fNIRS) to collect functional brain imaging data from Costa Rican farm workers enrolled in an epidemiological study on the health effects of chronic pesticide exposure. While couched in this perspective, we focus on the methodological considerations that are necessary to conduct a mobile fNIRS study in a diverse range of environments. Thus, this guide is intended to be generalizable to all research scenarios and projects in which fNIRS may be used to collect functional brain imaging data in epidemiological field surveys. https://doi.org/10.1289/EHP2049

Variability and predictors of weekly pesticide exposure in applicators from organic, sustainable and conventional smallholder farms in Costa Rica

“…Detailed methods for the PESTROP project have been described elsewhere 29 31. Briefly, between June and September 2016 (season during which pesticide applications intensify due to increased rain18), we enrolled 300 workers from 90 farms (9 organic, 19 sustainable and 62 conventional farms; between 1 and 18 workers per farm).…”

Capturing Human Interaction in the Virtual Age: A Perspective on the Future of fNIRS Hyperscanning

“…Efforts from the broader fNIRS community will be required to make fNIRS truly ready for realistic scenarios. With respect to hardware, this includes increased device portability and robustness (e.g., with respect to movement and environmental light), increased optode number to cover more cortical areas, and short-channels to account for extra-cerebellar blood flow that may contaminate fNIRS signals (Brigadoi and Cooper, 2015 ; Baker et al, 2017 ; Herold et al, 2017 ). Furthermore, efforts should be made with respect to standardizing fNIRS procedures, such as optode placement, data processing, choice of activation proxy (i.e., oxy- vs. de-oxygenated hemoglobin) (Brigadoi et al, 2014 ; Tachtsidis and Scholkmann, 2016 ; Herold et al, 2017 ; Di Lorenzo et al, 2019 ), and adoption of standardized open-source fNIRS-specific data analysis packages (e.g., HOMER2 , NIRS SPM , nirsLAB , open-potato , etc.).…”

“…Specifically, fNIRS hyperscanning has highlighted inter-brain coherence (i.e., correlation of cortical activity between brains) that occurs during social interactions, such as cooperation (Cui et al, 2012 ; Yang et al, 2020 ), and is often associated with enhanced behavioral metrics of interaction (Baker et al, 2016 ). Importantly, given fNIRS' relatively robust tolerance to movement and methodological flexibility, hyperscanning in this modality allows researchers to observe the neural correlates of shared human neural activity in naturalistic environments that are often not feasible in other modalities, such as fMRI or EEG (Scholkmann et al, 2013 ; Baker et al, 2017 ; Quaresima and Ferrari, 2019 ; Gvirts and Perlmutter, 2020 ). The dramatic increase in fNIRS hyperscanning research has spurred the publication of several systematic reviews, to which we refer the interested reader (Babiloni and Astolfi, 2014 ; Wang et al, 2018 ; Czeszumski et al, 2020 ).…”

Manganese exposure and working memory-related brain activity in smallholder farmworkers in Costa Rica: Results from a pilot study

“…We measured brain activity during a letter-retrieval working memory task (Sternberg, 1969) with a portable fNIRS device (NIRSport, NIRx Medical Technologies, LLC). Details of fNIRS methods utilized in this study have been described elsewhere (Baker et al, 2017). Briefly, we projected near-infrared light with wavelengths of 760 nm and 850 nm into the cortex of each participant's brain, and recorded samples of data at a rate of 7.81 Hz.…”

“…Functional neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRS), measure localized changes in cerebral blood flow related to brain activity at the neural level and have the potential to elucidate the neuropathological pathway through which chemical exposures affect the brain (Boas et al, 2014;Horton et al, 2014). While fMRI is considered the gold standard in functional neuroimaging due to its high spatial resolution, fNIRS is emerging as a convenient and lowcost alternative, especially when working in remote regions (Baker et al, 2017). Although fNIRS has a lower signal-to-noise ratio than fMRI, the two methods have been found to correlate highly across a variety of cognitive tasks (Cui et al, 2011).…”