Physiological significance of R-fMRI indices: Can functional metrics differentiate structural lesions (brain tumors)?

Abstract

Resting-state functional MRI (R-fMRI) research has recently entered the era of “big data”, however, few studies have provided a rigorous validation of the physiological underpinnings of R-fMRI indices. Although studies have reported that various neuropsychiatric disorders exhibit abnormalities in R-fMRI measures, these “biomarkers” have not been validated in differentiating structural lesions (brain tumors) as a concept proof. We enrolled 60 patients with intracranial tumors located in the unilateral cranialcavity and 60 matched normal controls to test whether R-fMRI indices can differentiate tumors, which represents a prerequisite for adapting such indices as biomarkers for neuropsychiatric disorders. Common R-fMRI indices of tumors and their counterpart control regions, which were defined as the contralateral normal areas (for amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo) and degree centrality (DC)) and ipsilateral regions surrounding the tumors (for voxel-mirrored homotopic connectivity (VMHC)), were comprehensively assessed. According to robust paired t-tests with a Bonferroni correction, only VMHC (Fisher's r-to-z transformed) could successfully differentiate substantial tumors from their counterpart normal regions in patients. Furthermore, ALFF and DC were not able to differentiate tumor from normal unless Z-standardization was employed. To validate the lower power of the between-subject design compared to the within-subject design, each metric was calculated in a matched control group, and robust two-sample t-tests were used to compare the patient tumors and the normal controls at the same place. Similarly, only VMHC succeeded in differentiating significant differences between tumors and the sham tumor areas of normal controls. This study tested the premise of R-fMRI biomarkers for differentiating lesions, and brings a new understanding to physical significance of the Z-standardization.

Eight‐week antidepressant treatment reduces functional connectivity in first‐episode drug‐naïve patients with major depressive disorder

“…The third limitation is the sample size of our study. Much larger sample size is needed for between-subject designs than within-subject designs to detect an effect (Fan et al, 2019). Thus, null results in comparing MDD patients before treatment and HCs could be due to this design difference.…”

Study on acupuncture in the treatment of painful diabetic peripheral neuropathy based on rs-fMRI: a protocol for systematic review and meta-analysis

“…Studies have evaluated abnormal brain activity in patients with diabetic neuropathy treated with acupuncture using ALFF, ReHo and FC yet these studies have reported inconclusive findings. [24][25][26][27][28] Moreover, previous studies on acupuncture for PDPN have been focused on changes in the spinal level rather than the central level due to the limitations of research techniques. Recently, rapid developments in rs-fMRI technology have allowed it to be widely used to investigate changes in brain function changes in a variety of diseases.…”