Progress in non-invasive neuromodulation based on consciousness-related neural circuits: a narrative review

Disorders of Consciousness (DOC) are characterized by abnormal function or disrupted connectivity of consciousness-related neural circuits, mainly presenting as Vegetative State/Unresponsive Wakefulness Syndrome (VS/UWS) and Minimally Conscious State (MCS), which impose a heavy burden on patients' families and society. Non-Invasive Brain Stimulation (NIBS) has emerged as a core research direction for DOC treatment due to its non-invasiveness, ease of operation, and favorable safety profile. Based on the classification of consciousness-related neural circuits, this review systematically summarizes the research progress of central and peripheral non-invasive neuromodulation techniques, including their potential regulatory mechanisms on core circuits (such as the frontoparietal network, cortico-thalamocortical circuit, and ascending reticular activating system), clinical evidence, and synergistic effects of combined therapies. Studies have shown that techniques like Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) targeting the frontoparietal network, Low-Intensity Transcranial Focused Ultrasound (LITUS, also referred to as Transcranial Focused Ultrasound [TUS]/transcranial Focused Ultrasound [tFUS] in the field) and Temporal Interference (TI) regulating the cortico-thalamocortical circuit, and Median Nerve Stimulation (MNS) activating the ascending reticular activating system have demonstrated certain efficacy in improving consciousness in MCS patients, while the evidence for efficacy in VS/UWS patients remains weak due to small sample sizes, lack of control groups and insufficient statistical power. Combined therapies such as TMS + MNS and Transcranial Focused Ultrasound LITUS+TMS exhibit significantly superior synergistic effects compared to monotherapies. By horizontally comparing the advantages and limitations of various techniques, this review proposes personalized treatment recommendations based on the characteristics of neural circuit damage. It also points out that future research should optimize stimulation parameters, clarify the specificity of circuit regulation, and verify long-term efficacy through large-sample randomized controlled trials (RCTs), aiming to provide a reference for the standardized and precise application of NIBS in DOC treatment.