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 may reflect cortical hyperarousal. Meanwhile, ID patients exhibited weaker PAC values for alpha–beta and beta–gamma PAC. Beta–gamma PAC was found to be associated with sleep patterns and cognition in major depression disorder (Liu et al., 2022). Thus, we suggested that a possible complicated relationship existed among PAC, sleep, and cognition in ID patients. A comprehensive cognition assessment should be included in the future to support this hypothesis. Furthermore, we examined the relationship between PAC values and the PSQI and ISI scores. As depicted in Figure 4d, PAC values were significantly negatively correlated with PSQI and ISI scores at baseline; that is, ID patients with lower PAC values showed worse sleep quality, as demonstrated by higher PSQI and ISI scores. The abnormal decrease in PAC values in ID patients may be associated with decreased control from theta rhythm to gamma activity.
