As an indicator of synchronization of distinct neural oscillations with different frequencies that might support dynamic communication within the brain, PAC has received much recent attention in the study of neurological disorders, for example, attention‐deficit hyperactivity disorder, Alzheimer's dementia, autism spectrum disorder, bipolar disorder, depression, obsessive–compulsive disorder, social anxiety disorder, and schizophrenia (de Hemptinne et al., 2013; Devergnas et al., 2019; Schapira et al., 2009). In the present study, ID patients exhibited weaker PAC values for theta–gamma in the frontal region (Figure 3). The frontal cortex is a key node in arousal circuitry and is involved in multiple neuronal levels of metabolites such as corticosterone, adrenocorticotropic hormone, or thyrotropin. Our results are consistent with those of a previous study on sleep disorders, in which patients with obstructive sleep apnea had significantly lower theta‐gamma PAC (Gouveris et al., 2022). Theta rhythm is a marker of sleepiness during wakefulness and early phases of spontaneous sleep. Gamma rhythms are related to learning, memory, and consciousness. Many studies have reported significantly increased gamma activity during wakefulness in ID patients (Zhao et al., 2021), this
