Functional Near Infrared Spectroscopy: A Promising Tool for Brain Function Mapping in Children with Autism Spectrum Disorder

ABSTRACT: Autism spectrum disorder (ASD) is a developmental disorder of the brain characterized by difficulties in social interaction and communication and stereotyped behaviors. Key brain regions involved in social functioning that are often impaired in individuals with ASD include the mesial prefrontal cortex, amygdala, superior temporal sulcus (STS), temporoparietal junction, and temporal pole. Additionally, areas such as the inferior frontal gyrus and inferior parietal lobule, which are part of the mirror neuron system, as well as the dorsolateral prefrontal cortex (DLPFC), associated with executive function, are also implicated. Various brain imaging techniques like functional magnetic resonance imaging (fMRI), electroencephalography, and magnetoencephalography have indicated dysfunctional brain connectivity in individuals with autism. fMRI is a commonly used imaging method for studying brain connectivity patterns in those with autism; however, its effectiveness can be hindered by technical challenges and the difficulty of obtaining high-quality images in the awake state in these individuals. Functional near-infrared spectroscopy (fNIRS) is a relatively new technique that has been explored to understand hemodynamic brain responses and connectivity in autism. Over the past decade, numerous studies have utilized fNIRS to examine individuals with ASD, including infants, children, and adults, both at rest and during various tasks. In this review article, we first outline the fundamental principles and technology behind fNIRS, along with its advantages and limitations, followed by the fNIRS studies conducted on children with ASD during resting states, as well as during various tasks such as joint attention, emotion recognition, and language processing.