Measuring mild cognitive impairment whole-brain electroencephalography phase-amplitude coupling connectivity using polar mutual information

<i>Objective</i>. A novel phase-amplitude coupling (PAC) estimator is proposed to address the limitations of existing PAC estimators in terms of insufficient application scenarios.<i>Approach</i>. The polar mutual information (PoMI) method is compared with the currently dominant PAC estimators, mean vector length, Kullback-Libler distance, general linear model, and phase-locking value, focusing on analyzing its characteristics in terms of coupling strength sensitivity, data length dependency, noise resistance, and coupling frequency band sensitivity. We recruited 54 healthy controls and 41 mild cognitive impairment (MCI) patients and assessed their cognitive level and whole-brain PAC connectivity by neurophysiological tests and resting electroencephalography, respectively.<i>Main results</i>. The PoMI algorithm is sensitive to changes in coupling strength, exhibits low dependence on data length, is insensitive to noise variations, and produces stable computational outcomes. Therefore, the PoMI algorithm can quantify the PAC phenomenon in neural oscillations. Furthermore, reduced PAC connectivity in the frontal lobe of patients with MCI, while PAC activity is enhanced in the parietal and occipital lobes. The results indicate that alterations in prefrontal PAC connectivity in MCI patients may represent one manifestation of neuronal group degeneration in the prefrontal cortex of these individuals.<i>Significance</i>. The PoMI algorithm can effectively evaluate the PAC phenomenon in neural oscillations and can be used as a PAC estimator. (Approved No. of ethic committee: 2024-P2-210-02).