Identifying the effects of visceral interoception on human brain connectome: A multivariate analysis of covariance of fMRI data

Sources of variations in the neural circuitry of the human brain and interrelationship between intrinsic connectivity networks (ICNs) are still a matter of debate and ongoing research. Here, we applied a multivariate analysis of covariance (MANCOVA) based on high-dimensional independent component analysis (ICA) to identify the effects of interoception and related variables on human brain connectome. Fifteen healthy right-handed subjects (all females, age range 21 - 48 years; mean age = 30.3, SD = 8.7 years) underwent a blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) that included continuous intravesical saline infusion and drainage. The design matrix included the intravesical fullness, subject fullness rating, normalized right and left insula thickness, age, and neuropsychological assessments (Mini-Mental State Exam; MMSE, and Hospital Anxiety and Depression Scale; HADS) as covariates of interest. Univariate tests were also performed with a reduced design matrix (p <; 0.05, corrected for multiple comparisons using false discovery rate) to study the nature and extent of the relationship between these covariates and three ICA outcome measures, namely, the spatial map intensity, frequency spectral power, and functional network connectivity. Results showed significant effects of interoception (intravesical fullness) on spatial map intensity of the salience network (anchored by insula and anterior cingulate cortex) and the frontoparietal central executive network, The left and right insula thickness influenced the spatial map intensity of the subcortical network, and the attention/cognitive and default-mode networks, respectively. The intravesical fullness also showed an effect on the spectral power of the subcortical network. Further investigations of the effect of internal (bodily) sensations on the ICN properties can provide an invaluable tool for understanding the role of interoception in health and illness.