Abstract
Cochlear implants (CIs) have revolutionized how we treat hearing impairment. Despite major technological and clinical advances, some CI children's language abilities remain below those of their age-matched peers, and there is still considerable individual variability in final outcomes. One important factor underlying this may be individual differences in brain plasticity before and after implantation. However, the neural changes induced in the developing brain by deafness, language deprivation, and the restoration of hearing due to implantation are little understood, in part because the methodological options available are limited. Recently, functional near-infrared spectroscopy (fNIRS) has emerged as a fully CI-compatible, infant-friendly, non-invasive, and inexpensive technique that holds the promise of shedding light on the neural mechanisms accompanying deafness and CI use. Here, we review the existing fNIRS studies with developmental populations. We then discuss the methodological challenges that using fNIRS with CI children raise. Finally, we describe open questions that fNIRS has the potential to answer. We conclude that fNIRS is a powerful tool to investigate the neural mechanisms and changes brought about by deafness and the subsequent restoration of hearing with CI.