Evaluation of Prefrontal Cortex Activation and Static Balance Mechanisms in Adolescent Idiopathic Scoliosis Using fNIRS

Abstract

Background and Objectives: In this study, the role of oxyhemoglobin (HbO) in subregions of the prefrontal cortex during a static balance task under eyes-open and eyes-closed conditions was investigated in adolescent idiopathic scoliosis (AIS) using functional near-infrared spectroscopy (fNIRS), a powerful neuroimaging tool that enables more natural and flexible measurement in the analysis of balance mechanisms and motor tasks. Materials and Methods: Hemodynamic changes in the right and left dorsolateral cortex (DLPFC), frontopolar prefrontal cortex, and orbitofrontal cortex were analyzed in 16 healthy controls and 15 individuals with AIS. The statistical results were supported by HbO contrast maps. Results: Significant differences were found in the cortical activity patterns between the AIS and control groups. The AIS group had lower HbO concentrations than the control group in the eyes-closed condition and completely differed from the control group by showing more active HbO concentrations in the DLPFC regions than in the frontopolar regions. In the eyes-open condition, it was found that the maximum HbO value was reached in the frontopolar regions, and this value was weakened and observed throughout the left frontopolar region. Discriminative differences were also found in the orbitofrontal region in the eyes-closed static balance condition. Conclusions: The results obtained were evaluated and discussed in terms of postural balance compensation, differences in neural pathways, and the conscious balance mechanism. It was determined that the AIS group tended to utilize a conscious balance mechanism in the eyes-closed static balance condition and developed its own balance compensation mechanism in the eyes-open static balance condition. This study concludes that fNIRS is a powerful tool in the evaluation of balance and control mechanisms and can be used effectively in the evaluation of rehabilitation-oriented development in AIS.

Keywords: adolescent idiopathic scoliosis; brain activation; functional near-infrared spectroscopy; oxyhemoglobin; postural control; prefrontal cortex activity.

Figure 1

fNIRS optode placement and areas of interest: (a) fNIRS configuration covering the prefrontal cortex (red circles are source channels, blue circles are detector channels, and their interconnections are shown); (b) channels represented by the channel/detector pairs used, their corresponding Brodmann regions, the MNI coordinates, the specificity percentages, and the corresponding cortical structures.