“…However, some functional connectivity is enhanced, especially in mild cognitive impairments (Zhang et al, 2016 ). Therefore, to estimate the cognitive state in older individuals, capturing disease-specific (Zhou and Seeley, 2014 ; van Dellen et al, 2015 ; Zhang et al, 2016 ; Nobukawa et al, 2020a ; Torres-Simón et al, 2022 ), age-specific (Scally et al, 2018 ; Ando et al, 2022 ), and level-of-cognitive-functional-specific (Nobukawa et al, 2020b ) spatial patterns of functional connectivity is important. Moreover, among the many approaches to estimate functional connectivity, such as coherence measure and transform entropy, instantaneous phase synchronization, typified as the phase lag index (PLI), is an effective approach for estimating functional connectivity with higher spatial resolution compared to other synchronization approaches, by virtue of suppressing the influence of volume conduction (Stam et al, 2007b ; Tobe and Nobukawa, 2022 ).…”