Increased spontaneous fronto-central oscillatory power during eye closing in patients with multiple somatic symptoms.

Functional somatic symptoms (FSS) are typically associated with excessive thoughts, feelings and behaviors related to the physical symptoms whether these symptoms are unequivocally associated with a diagnosed medical condition. However, less evidence is available concerning the neurocognitive deficits underlying these features of FSS. This study aimed to examine the resting-state oscillatory activities during both eye-opening and eye-closure states in individuals with FSS. Sixty-six FSS patients screened with PHQ-15 received two 10-minute sessions of EEG assessments. All completed clinical measurements on depression, anxiety, and psychological measurements on personality traits and alexithymia. Patients scoring high on PHQ-15 (the multiple somatic symptom (MSS) or SS-high group) demonstrated increased powers in central channels (C3 and C4) in low-beta band and in the left-frontal channel (F3) in high-gamma band, during eye-closure states. Patients with higher scores in depression were more likely to be classified as the SS-high group. SS-high patients demonstrated increased difficulties in describing and identifying emotions, and less reduced day-dreaming. The combined findings in increased fronto-central high-frequency activities and alexithymia measures suggest MSS patients are associated with enhanced internally-oriented thinking and cognitive simulation which may lead to intensified feelings of simulated events and misattribution of symptoms. Future treatments should focus on eliminating cognitive bias and enhancing accuracy in interoceptive awareness.