Combined Regulatory Effects of 40 Hz eTNS and Multisensory Stimulation on Brain Networks

A Study on the Enhancing Effects of 40 Hz Combined Trigeminal-Sensory Stimulation on Working Memory

The purpose of this study is to investigate the independent and interactive effects of 40Hz auditory, visual, and external trigeminal nerve stimulation (eTNS) on brain state dynamics and functional connectivity. While 40Hz visual and auditory sensory stimulation have been explored for potential cognitive and therapeutic benefits, the underlying mechanisms on large-scale brain networks and the potential effects of combining multiple modalities remain unclear.

This study aims to determine whether multimodal co-stimulation genuinely compounds network-level effects or if targeted dual-pairings are more efficient for brain network reorganization. In this within-subject study, 23 participants will receive all eight possible combinations of 40Hz auditory, visual, and eTNS (targeting the maxillary branch) in a randomized order. Each stimulation condition will last for 5 minutes, separated by 1-minute inter-stimulus intervals. Continuous electroencephalography (EEG) will be recorded throughout the procedures to evaluate brain responses. The collected EEG data will be analyzed using microstate analysis, functional connectivity analysis, and graph-theoretic network analysis. Ultimately, the study seeks to understand how these non-invasive stimulation techniques, independently and together, drive large-scale network reorganization and optimize the balance between local specialization and global integration in the brain.

Study Overview

• Status: Recruiting
• Conditions: Healthy Participants
• Intervention / Treatment: Device: 40 Hz External Trigeminal Nerve Stimulation; Device: 40 Hz Auditory Stimulation; Device: 40 Hz Visual Stimulation; Other: Sham Stimulation

Detailed Description

Physical neuromodulation at 40 Hz has emerged as a promising therapeutic approach, with visual and auditory stimulation demonstrating the capacity to entrain gamma oscillations and confer cognitive benefits. Analogous effects have also been observed with electrical approaches, including external trigeminal nerve stimulation (eTNS). While the prevailing assumption in the field suggests that combining multiple sensory modalities will more comprehensively recruit distributed brain circuitry and yield greater therapeutic effects, the mechanistic foundations of this additive hypothesis remain contested. Furthermore, recent evidence indicates that network-level reorganization, rather than localized gamma entrainment, may represent a more causally relevant substrate for these cognitive improvements.

This study is designed to systematically characterize the independent and interactive effects of 40Hz auditory, visual, and eTNS stimulation on brain state dynamics, functional connectivity, and graph-theoretic network properties. The trial employs a fully crossed 2×2×2 within-subject design. A total of 23 participants will undergo all eight possible combinations of 40Hz stimulation modalities: sham (no stimulation), auditory only, visual only, eTNS only, auditory + visual, auditory + eTNS, visual + eTNS, and the three-way combination of auditory + visual + eTNS.

During the experimental session, the eTNS will specifically target the maxillary branch of the trigeminal nerve. The eight stimulation conditions will be administered in a randomized order for each participant. Each stimulation block will last for 5 minutes, separated by 1-minute inter-stimulus intervals to prevent carry-over effects.

Continuous electroencephalography (EEG) will be recorded throughout the session using a 32-channel eego™ mylab system (ANT Neuro, Netherlands) to capture real-time cortical responses. Following data acquisition, standard preprocessing pipelines will be applied, including notch filtering, 0.5-45Hz bandpass filtering, average re-referencing, ICA-based artifact rejection, and bad channel interpolation.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Xue-Juan Yang, Phd; Phone Number: 86-029-81891070; Email: xjyang@xidian.edu.cn
• Study Contact Backup: Name: Xue-Juan Yang; Phone Number: 15691826100; Email: xjyang@xidian.edu.cn

Study Locations

• China
  • Shaanxi
    • Xi'an, Shaanxi, China, 71000
      • Recruiting
      • Xidian University
      • Contact: Xue-Juan Yang; Phone Number: +8615691826100; Email: xjyang@xidian.edu.cn
      • Contact: Email: xjyang@xidian.edu.cn
      • Principal Investigator: Chen cheng', MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy adults aged ≥18 years old.
• Normal or corrected-to-normal vision and hearing (essential for 40Hz visual and auditory stimulation).
• Right-handedness.
• Willing to participate in the study and capable of providing written informed consent.

Exclusion Criteria:

• Personal or family history of epilepsy or seizures (crucial safety criteria for 40Hz flicker and electrical stimulation).
• History of any neurological or psychiatric disorders.
• Presence of metallic implants in the head, cardiac pacemakers, or other implanted electronic medical devices.
• Skin lesions, infections, or hypersensitivity at the eTNS stimulation site (maxillary branch of the trigeminal nerve).
• Current use of psychoactive medications or substances that may significantly alter EEG signals or brain state dynamics.
• Pregnant or lactating individuals.
• Poor sleep quality or irregular sleep-wake cycles prior to the experiment.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Experimental Crossover Group; All participants are enrolled in this single crossover arm. Each participant will receive all eight combinations of 40Hz stimulation (auditory, visual, and external trigeminal nerve stimulation [eTNS] targeting the maxillary branch) in a randomized order, including a sham condition. Each stimulation condition lasts for 5 minutes, separated by 1-minute inter-stimulus intervals.

Device: 40 Hz External Trigeminal Nerve Stimulation; Electrical stimulation targeting the maxillary branch of the trigeminal nerve at a frequency of 40 Hz; Device: 40 Hz Auditory Stimulation; Auditory sensory stimulation delivered at 40 Hz for 5-minute durations; Device: 40 Hz Visual Stimulation; Visual sensory stimulation delivered at a frequency of 40 Hz for 5-minute durations; Other: Sham Stimulation; Inactive control stimulation designed to mimic the sensory experience of the active modalities without delivering actual 40 Hz therapeutic stimulation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Whole-Brain Functional Connectivity (Phase-Locking Value)	Day1 (during the single experimental session)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
EEG Microstate Dynamics (Mean Duration and Segment Density)	Brain state dynamics evaluated via microstate analysis of global field power (GFP) peaks. Primary metrics extracted include the mean duration and segment density (occurrence rate per minute) of identified microstate classes to assess modality-specific regulation.	Up to 1 hour (during the single experimental session)
Global Efficiency	Large-scale brain network organization will be assessed using graph-theoretic topology analysis based on continuous EEG recordings. Global efficiency will be calculated to evaluate network-wide communication efficiency across a sparsity threshold range of 0.1 to 0.5 under different 40Hz stimulation conditions.	Day1 (during the single experimental session)
Small-World Propensity of Brain Networks	Large-scale brain network organization will be assessed using graph-theoretic topology analysis based on continuous EEG recordings. Small-world propensity will be calculated to evaluate the balance between local specialization and global integration across a sparsity threshold range of 0.1 to 0.5 under different 40Hz stimulation conditions.	Day 1 (during the single experimental session)

Collaborators and Investigators

• Sponsor: Xidian University
• Collaborators: Xi'an Central Hospital
• Investigators: Principal Investigator: Xue-Juan Yang, Xidian University

Study record dates

Study Major Dates

• Study Start (Estimated): June 15, 2026
• Primary Completion (Estimated): June 26, 2026
• Study Completion (Estimated): June 26, 2026

Study Registration Dates

• First Submitted: June 12, 2026
• First Submitted That Met QC Criteria: June 21, 2026
• First Posted (Actual): June 25, 2026

Study Record Updates

• Last Update Posted (Actual): June 25, 2026
• Last Update Submitted That Met QC Criteria: June 21, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Functional connectivity; EEG microstates; External trigeminal nerve stimulation (eTNS); 40Hz stimulation; Multimodal neuromodulation; Brain network reorganization; Network topology
• Other Study ID Numbers: 20260612

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD), particularly raw continuous electrophysiological recordings (EEG), contains sensitive and potentially identifiable biometric information. In accordance with institutional data security policies and ethical guidelines regarding participant privacy, raw IPD will not be made publicly available. However, aggregated statistical data and summary results will be published in peer-reviewed journals. De-identified, summary-level data or analytical scripts may be shared by the corresponding author upon reasonable academic request, subject to formal institutional review and approval.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No