Electrical Nerve Stimulation During Sleep for Memory Consolidation
ConditionHealthy Volunteers (HV)
Trial statusRecruiting
Trial phaseNot applicable
Trial typeInterventional
Biological sexAll
Age18-35
SponsorXidian University
About this trial
The purpose of this study is to investigate the effects of transcutaneous electrical nerve stimulation (eTNS) applied during sleep on memory consolidation and brain-body physiological coupling. Healthy college students will participate in four overnight sleep sessions in a standard sleep laboratory.
Before going to sleep, participants will learn and complete two cognitive tasks: a motor sequence tapping task to assess procedural memory, and an N-back task to assess working memory. During the night, participants will receive either 2 Hz eTNS, 120 Hz eTNS, or a sham (placebo) stimulation on their forehead in a randomized order. Throughout the night, researchers will record their sleep using polysomnography (PSG), along with continuous monitoring of heart rate (ECG) and breathing (respiration). Upon waking the next morning, participants will be re-tested on both memory tasks.
The primary objective is to determine whether eTNS during sleep can improve behavioral performance on procedural and working memory tasks overnight. Secondary objectives include analyzing the stimulation's effects on specific sleep brain wave patterns (such as slow oscillations and sleep spindles) and exploring the coupling mechanisms between brain activity, heart rhythms (Heartbeat Evoked Potentials), and respiration during sleep.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Healthy young adults (e.g., college students), aged generally between 18 and 30 years.
Right-handed.
Body Mass Index (BMI) ≤ 30 kg/m².
Capable of fully comprehending the experimental procedures and voluntarily signing the informed consent form.
Disqualifiers
History or current presence of neurological disorders, psychiatric disorders, or brain damage.
History or current presence of cardiovascular diseases (e.g., arrhythmias or abnormal nocturnal heart rate).
Presence of depressive or anxiety symptoms (assessed by Patient Health Questionnaire-9 [PHQ-9] score > 9, or Generalized Anxiety Disorder-7 [GAD-7] score > 9).
Presence of sleep disturbances or poor sleep quality (assessed by Insomnia Severity Index [ISI] score > 8, or Pittsburgh Sleep Quality Index [PSQI] score > 10).
Trial design
Design model
Crossover
Treatments tested in this trial
120 Hz Transcutaneous Electrical Nerve Stimulation
DeviceParticipants will receive 120 Hz transcutaneous electrical nerve stimulation (eTNS) during nighttime sleep. The stimulation is delivered via a current source stimulator connected to self-adhesive silicone electrodes placed above the left and right eyebrows. The stimulation consists of biphasic rectangular pulses with a 250 μs pulse width at a frequency of 120 Hz. It is delivered in continuous cycles of 30 seconds on and 30 seconds off. Before sleep, the current intensity is individually titrated to elicit a mild tingling sensation (corresponding to a score of 3-4 on a numerical rating scale) that will not disrupt the participant's sleep. The stimulation protocol automatically terminates after a duration of 8 hours.
2 Hz Transcutaneous Electrical Nerve Stimulation
DeviceParticipants will receive 2 Hz transcutaneous electrical nerve stimulation (eTNS) during nighttime sleep. The stimulation is delivered via a current source stimulator connected to self-adhesive silicone electrodes placed above the left and right eyebrows. The stimulation consists of biphasic rectangular pulses with a 250 μs pulse width at a frequency of 2 Hz. It is delivered in continuous cycles of 30 seconds on and 30 seconds off. Before sleep, the current intensity is individually titrated to elicit a mild tingling sensation (corresponding to a score of 3-4 on a numerical rating scale) that will not disrupt the participant's sleep. The stimulation protocol automatically terminates after a duration of 8 hours.
Sham Stimulation (Placebo)
DeviceParticipants will receive a sham stimulation designed to serve as a placebo control. The equipment setup, including the placement of self-adhesive silicone electrodes above the left and right eyebrows, is identical to the active eTNS conditions. The current intensity is initially adjusted before sleep to elicit the same mild tingling sensation (a score of 3-4 on a numerical rating scale). However, to maintain double-blinding without providing a therapeutic dose, the stimulator only delivers current output during the first 2 minutes of the night (i.e., exactly two cycles of 30 seconds on and 30 seconds off). After these initial 2 minutes, the current output ceases entirely for the remainder of the 8-hour sleep period.
Treatment groups
30 Participants
are divided into 3 treatment groupsGroup A: 120 Hz Transcutaneous Electrical Nerve StimulationExperimental treatment 1 intervention
Group B: 2 Hz Transcutaneous Electrical Nerve StimulationExperimental treatment 1 intervention
Group C: Sham Stimulation (Placebo)Placebo comparator 1 intervention
Trial outcomes
Primary outcomes
1
Change in Procedural Memory Performance
Procedural memory consolidation will be assessed using the classic sequential finger-tapping task (SFTT). Performance improvement is calculated as the difference in speed (number of correct sequences typed) and accuracy between the pre-sleep training/testing session and the post-sleep testing session. A larger positive difference indicates better procedural memory consolidation overnight.
Time frame
Assessed pre-sleep (approx. 21:00-22:00) and post-sleep (approx. 07:00-08:00 the following morning), representing an overnight interval of approximately 10 hours.Secondary outcomes
1
Change in Working Memory Performance
Working memory performance will be assessed using the 2- to 5-back task. Outcome metrics include reaction time and accuracy (hit rate and false alarm rate). The overnight change is calculated by comparing the performance in the post-sleep testing session to the pre-sleep baseline session. Higher accuracy and shorter reaction times indicate improved working memory function.
Time frame
Assessed pre-sleep (approx. 21:00-22:00) and post-sleep (approx. 07:00-08:00 the following morning), representing an overnight interval of approximately 10 hours.2
Sleep Architecture and Sleep Efficiency
Sleep architecture will be derived from PSG scoring according to the American Academy of Sleep Medicine (AASM) criteria. Key metrics include Total Sleep Time (TST), Sleep Efficiency (SE, calculated as TST divided by Time in Bed), and the percentage of time spent in different sleep stages (N1, N2, N3, and REM sleep). This ensures the stimulation does not negatively disrupt normal sleep patterns.
Time frame
Continuously recorded during the 8-hour nighttime sleep period.Other outcomes
1
Sleep Slow Oscillation (SO) Density and Amplitude
Extracted from continuous Polysomnography (PSG) recordings (specifically at C3 and C4 channels). SO density (number of slow oscillations per minute) and peak-to-peak amplitude will be analyzed during Non-Rapid Eye Movement (NREM) sleep stages 2 and 3 to evaluate the depth and quality of slow-wave sleep.
Time frame
Continuously recorded during the 8-hour nighttime sleep period (from lights out at 23:00 to waking up between 07:00 and 08:00).2
Sleep Spindle Density and Amplitude
Extracted from PSG recordings at central electrodes (C3, C4). Fast sleep spindle density (number of spindles per minute) and amplitude will be calculated during NREM sleep stages 2 and 3.
Time frame
Continuously recorded during the 8-hour nighttime sleep period.3
Slow Oscillation-Spindle Coupling
This coupling will be evaluated by calculating the SO-spindle coupling ratio (the proportion of spindles coupled with SOs relative to the total number of spindles) and the preferred phase angle of spindle maxima relative to the SO phase. This metric reflects the coordination of memory-related brain rhythms.
Time frame
Continuously recorded during the 8-hour nighttime sleep period.4
Brain-Body Coupling: SO-Respiration Synchronization
Evaluated by analyzing the phase-locking or temporal synchronization between respiratory phases (extracted from simultaneous respiratory monitor data) and the occurrence/phase of sleep slow oscillations (extracted from EEG) during NREM sleep.
Time frame
Continuously recorded during the 8-hour nighttime sleep period.Sponsors and contacts
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Source ClinicalTrials.gov