An Online Database of Infant Functional Near InfraRed Spectroscopy Studies: A Community-Augmented Systematic Review

Abstract

Until recently, imaging the infant brain was very challenging. Functional Near InfraRed Spectroscopy (fNIRS) is a promising, relatively novel technique, whose use is rapidly expanding. As an emergent field, it is particularly important to share methodological knowledge to ensure replicable and robust results. In this paper, we present a community-augmented database which will facilitate precisely this exchange. We tabulated articles and theses reporting empirical fNIRS research carried out on infants below three years of age along several methodological variables. The resulting spreadsheet has been uploaded in a format allowing individuals to continue adding new results, and download the most recent version of the table. Thus, this database is ideal to carry out systematic reviews. We illustrate its academic utility by focusing on the factors affecting three key variables: infant attrition, the reliability of oxygenated and deoxygenated responses, and signal-to-noise ratios. We then discuss strengths and weaknesses of the DBIfNIRS, and conclude by suggesting a set of simple guidelines aimed to facilitate methodological convergence through the standardization of reports.

Methodology for high-yield acquisition of functional near-infrared spectroscopy data from alert, upright infants

“…Consequently, in this study, we present data from the 22 and 30 mm distances grouped together. This lies within most of the range of separation distances cited in reviews (∼93%) 2,3 and also conforms to the distances recommended by Taga et al 20 …”

“…The instrument houses a total of 24 sources and 21 detectors (24 × 21) with an average laser power level of 200 μW at each wavelength for each source. 19 A study across all infant fNIRS research (to 2012) by Cristia et al 3 investigating the attrition rate (infant exclusion) as a function of the total number of sources and detectors (optodes) notes that using fewer than 20 fiber bundles results in a significant reduction in the number of infants excluded. This aligns with our own experience in which larger, bulkier probes fail to maintain consistent optical contact during infant motion, causing severe artifacts.…”

“…Upright infants pose several complications for the researcher in obtaining good quality fNIRS data. Analysis of infant studies of all age groupings by Cristia et al 3 and Lloyd-Fox et al 2 reveals that ∼40% of data (at the infant level) is rejected. This high attrition rate is usually attributed to low signal-to-noise or less compliant infant subjects, which can be specifically due to a range of factors such as motion artifacts, lack of optical contact due to hair obstruction, improper fit of the NIRS cap, fussiness, or inattentiveness.…”

“…Infants' cerebral hemodynamics have been studied using nearinfrared light for more than 18 years, with the first publication by Meek et al 1 in 1998. Notable reviews by Lloyd-Fox et al 2 covering the time frame from the first publication to April 2009 and an online database by Cristia et al 3 reviewing the literature to July 2012 indicate that there were 76 articles and theses, which report on 109 different studies across a range of age groups. There are two major infant groupings according to Cristia et al 3 that have been most commonly studied: newborns and 4-to 8-month-old infants.…”

“…There are two major infant groupings according to Cristia et al 3 that have been most commonly studied: newborns and 4-to 8-month-old infants. Studies by other groups, [4][5][6][7][8][9][10] in the age range of 5 to 7 months similar to the age range in our study, focused on the occipital, temporal, and parietal cortices.…”