Characterizing the Action-Observation Network Through Functional Near-Infrared Spectroscopy: A Review

Abstract

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that has undergone tremendous growth over the last decade due to methodological advantages over other measures of brain activation. The action-observation network (AON), a system of brain structures proposed to have “mirroring” abilities (e.g., active when an individual completes an action or when they observe another complete that action), has been studied in humans through neural measures such as fMRI and electroencephalogram (EEG); however, limitations of these methods are problematic for AON paradigms. For this reason, fNIRS is proposed as a solution to investigating the AON in humans. The present review article briefly summarizes previous neural findings in the AON and examines the state of AON research using fNIRS in adults. A total of 14 fNIRS articles are discussed, paying particular attention to methodological choices and considerations while summarizing the general findings to aid in developing better protocols to study the AON through fNIRS. Additionally, future directions of this work are discussed, specifically in relation to researching AON development and potential multimodal imaging applications.

Cerebral hemodynamic response during a live action-observation and action-execution task: A fNIRS study

“…Functional near-infrared spectroscopy (fNIRS) is an optical imaging tool that has gained the attention of the AON research community in recent years [26] Like fMRI, fNIRS is a brain imaging technique that measures changes in the oxygenation level of cerebral tissue as a proxy for brain activation. However, rather than relying on the use of large magnets, fNIRS uses near infra-red light to quantify the hemodynamic responses associated with neural activity by measuring changes in oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR) and total hemoglobin (HbT).…”

Using Functional Connectivity to Examine the Correlation between Mirror Neuron Network and Autistic Traits in a Typically Developing Sample: A fNIRS Study

“…Interestingly, the observation condition resulted in a greater number of bilateral connections than the execution condition (action observation: five inter-left and five inter-right hemisphere connections, action execution: four inter-left and three inter-right hemisphere connections). Traditional MNN analysis using fNIRS has shown that action observation elicits more bilateral activation when compared to execution [38], therefore it is not surprising that this is also captured through connectivity analyses. Additionally, the connections that have significantly greater connectivity in both conditions were connections within the left inferior parietal, right supramarginal and between the left supramarginal and left angular regions, which is consistent with previous findings of the link between bilateral inferior parietal lobe and the MNN [20].…”

“…In this study, fNIRS, which has several advantages compared to other neuroimaging techniques especially when studying motor tasks [38], was used to examine the MNN. Compared to fMRI, fNIRS has better temporal resolution, is more robust to movement artifact, and is ecologically valid, making it easy to use with developing and clinical population.…”

An fNIRS Study of Brain Lateralization During Observation and Execution of a Fine Motor Task

“…The action observation network (AON) is comprised of brain regions that are active when watching another person execute an action (Lepage and Théoret, 2006 ; Cross et al, 2009 ; Condy et al, 2021 ). Self-initiated motor actions using one side of the body lead to lateralized activation patterns in the brain, such that they primarily activate contralateral motor cortex with more limited activation in ipsilateral cortical regions (Colebatch et al, 1991 ; Rao et al, 1993 ; Pulvermüller et al, 1995 ).…”

“…For anatomical representation in the brain, the same observed movement would lead to greater left relative to right motor cortex activation. Although electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are the primary methods used to study the AON, brain lateralization of the AON is challenging to study using EEG due to limited spatial resolution or using fMRI due to effects of motion artifact on the MR signal (Condy et al, 2021 ).…”