The relationship between fractional amplitude of low-frequency fluctuations (fALFF) and the severity of neglect in patients with unilateral spatial neglect (USN) after stroke: A functional near-infrared spectroscopy study

Objective: Unilateral spatial neglect (USN) following right hemisphere stroke is more pronounced, severe, and persistent than in the left hemisphere. However, the pathophysiological mechanisms underlying USN remain largely unknown. This study aims to investigate the relationship between the fractional amplitude of low-frequency fluctuations (fALFF) in the right hemisphere of patients with post-stroke USN and the severity of neglect using resting-state functional near-infrared spectroscopy (fNIRS) technology. This could provide new theoretical insights into the subtle changes in the pathophysiology of spontaneous neural activity in brain regions of patients with USN.

Methods: Seventeen patients with post-stroke USN (USN group) and twenty-four control subjects (control group) were selected. A 22-channel fNIRS system was used to test the hemodynamic signals of the right hemisphere at rest for all subjects. Data preprocessing and analysis were performed using the NIRS-KIT toolbox. Patients in the USN group were assessed using the Behavioral Inattention Test-Conventional (BIT-C) and the Catherine Bergego Scale (CBS). Differences in fALFF values across channels between the two groups were compared, and the fALFF values from channels showing significant differences in the USN group were correlated with scores on scales evaluating the severity of USN.

Results: (1) Significant differences in fALFF values were observed between the USN and control groups in specific channels, with channels CH6 and CH11 showing significantly lower fALFF values in the USN group compared to the control group (p < 0.05), while channels CH12, CH16, and CH21 exhibited significantly higher fALFF values in the USN group (p < 0.05). (2) In patients with USN, fALFF values in CH12 were significantly negatively correlated with BIT-C scores (r = -0.4966, p = 0.0443), and fALFF values in CH21 were also significantly negatively correlated with BIT-C scores (r = -0.5270, p = 0.0318). (3) Only the fALFF values in CH21 were significantly positively correlated with CBS scores in patients with USN (r = 0.5512, p = 0.0236).

Conclusions: The severity of symptoms of neglect towards the left side in patients with USN may be related to compensatory neural functional activity in the right dorsolateral prefrontal cortex area.