Abstract
Studies of cortical function in the awake infant are extremely challenging to undertake with traditional neuroimaging approaches. Partly in response to this challenge, functional near-infrared spectroscopy (fNIRS) has become increasingly common in developmental neuroscience, but has significant limitations including resolution, spatial specificity and ergonomics. In adults, high-density arrays of near-infrared sources and detectors have recently been shown to yield dramatic improvements in spatial resolution and specificity when compared to typical fNIRS approaches. However, most existing fNIRS devices only permit the acquisition of ~20–100 sparsely distributed fNIRS channels, and increasing the number of optodes presents significant mechanical challenges, particularly for infant applications. A new generation of wearable, modular, high-density diffuse optical tomography (HD-DOT) technologies has recently emerged that overcomes many of the limitations of traditional, fibre-based and low-density fNIRS measurements. Driven by the development of this new technology, we have undertaken the first study of the infant brain using wearable HD-DOT. Using a well-established social stimulus paradigm, and combining this new imaging technology with advances in cap design and spatial registration, we show that it is now possible to obtain high-quality, functional images of the infant brain with minimal constraints on either the environment or on the infant participants. Our results are consistent with prior low-density fNIRS measures based on similar paradigms, but demonstrate superior spatial localization, improved depth specificity, higher SNR and a dramatic improvement in the consistency of the responses across participants. Our data retention rates also demonstrate that this new generation of wearable technology is well tolerated by the infant population.
Highlights
The investigation of cortical responses to controlled external stimuli has been fundamental to our improved understanding of the functional architecture of the human brain over the last few decades (Corbetta and Shulman, 2002; Kanwisher, 2010; Allison et al, 1999)
We describe the application of a prototype, wearable technology that permitted the acquisition of what we believe to be the first high-density Diffuse optical tomography (DOT) data-set in infants of 4 - 7 months of age, one of the most frequently studied age groups in developmental science (Cristia et al, 2013)
To our knowledge this is the first demonstration of a wearable, highdensity optical imaging technology in the infant population
Summary
The investigation of cortical responses to controlled external stimuli has been fundamental to our improved understanding of the functional architecture of the human brain over the last few decades (Corbetta and Shulman, 2002; Kanwisher, 2010; Allison et al, 1999). In HD-DOT, an array of sources and detectors is employed that is dense enough to provide a continuous distribution of both ‘short separation’ channels at ~10 mm sourcedetector separation and longer channels spanning the 10–40 mm range (White and Culver, 2010) This approach has been shown to significantly improve the disentanglement of extracerebral and cerebral haemodynamics (Funane et al, 2014), and has the capacity to yield cortical activation maps that approach the resolution of fMRI (Eggebrecht et al, 2014). Because these HD-DOT technologies require very large numbers of optodes, they compound the mechanical challenge associated with studying infant populations. In doing so we sought to demonstrate what can be achieved with optical neuroimaging in the developmental neurosciences
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