Assessing the Clinical Utility of tACS

Not Applicable

Completed

• Conditions: Hypervigilance; Sensory Disorders; Anxiety Disorders and Symptoms; Post Traumatic Stress Disorder
• Interventions: Device: Transcranial Alternating Current Stimulation

• Registration Number: NCT03305328
• Lead Sponsor: Florida State University

Brief Summary

The present study seeks to evaluate the clinical utility of repeated transcranial alternating current stimulation (tACS) by assessing long-term, lasting changes in oscillatory activity and subsequent changes in related behavioral processes of anxious arousal and sensory sensitivity. To date, only transient effects of tACS have been reported, lasting no longer than 30 to 70 minutes. In order to be truly impactful within a clinical setting, however, evidence for long-term effects of tACS is needed.

Detailed Description

Recent years have witnessed increasing recognition of "oscillopathies", neuropsychiatric disorders characterized by aberrations in the neural oscillations that orchestrate various mental activities. Transcranial alternating current stimulation (tACS) provides an effective way to directly modulate these oscillations in a non-invasive and frequency-specific manner, offering groundbreaking insights into the workings of the brain and, importantly, the development of novel treatments for these oscillopathies. However, evidence is lacking for the ability of tACS to induce long-term neural plasticity and lasting behavioral changes, which is critical for establishing the clinical utility of this novel intervention.

Here, we are administering 30 minutes of alpha-frequency tACS over occipitoparietal sites for four consecutive days to evaluate both transient and long-term changes in alpha oscillatory power and long-range, directed oscillatory connectivity. As both anxious arousal and sensory sensitivity are highly related to alpha oscillations, as well as numerous neuropsychiatric disorders, changes in these behavioral outcomes were subsequently evaluated to assess clinically-relevant outcomes of the repeated tACS protocol.

Study Timeline

• Study Start: 2016-07-29
• Primary Completion: 2017-03-31
• Study Completion: 2017-03-31
• Status Verified: 2017-10
• Study First Submitted: 2017-10-04
• Study First Submitted QC: 2017-10-04
• Last Update Submitted: 2017-10-04
• Study First Posted: 2017-10-09
• Last Update Posted: 2017-10-09

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 38

Inclusion Criteria

• Right-handed

Exclusion Criteria

• History of severe neurological disorder or traumatic brain injury
• Psychotropic medication use
• Metal plates/implants in head
• Pregnancy
• Implanted medical devices (e.x. pacemaker)

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Active	Transcranial Alternating Current Stimulation	Participants within the Active condition receive 30 minutes of alpha-frequency Transcranial Alternating Current Stimulation (tACS) stimulation for four consecutive days. Participants are stimulated at their baseline peak alpha frequency, or the frequency at which they exhibit maximal power within the 8 to 12 Hz range. Stimulation was administered over occipitoparietal sites, where tACS current models showed maximal effect over the dorsal extrastriate.
Sham Control	Transcranial Alternating Current Stimulation	Participants within the Sham condition receive 30 minutes of sham Transcranial Alternating Current Stimulation for four consecutive days, during which no current was passed. To control for awareness of the Sham stimulation, all Sham control participants receive a brief, 10 second pulse of random noise stimulation at the beginning and end of the 30 minutes.

Primary Outcome Measures

Name	Time	Method
Immediate and lasting changes in alpha oscillatory power and directed, long-range cortico-cortical connectivity.	Immediately before, immediately after, and 30 minutes after stimulation on the first day. Immediately before (24 hours after most recent stimulation), immediately after, and 30 minutes after stimulation on the final (fourth) day.	Occipitoparietal alpha power and long-range, directed oscillatory connectivity within the alpha frequency will be assessed from 2 minutes of eyes-open, resting-state electroencephalogram (EEG) activity. Oscillatory power will be estimated using the multitaper spectral estimation technique, averaging over the alpha frequency bin of 8-12 Hz. Directed connectivity will be assessed using spectral Granger causality within the 8-12 Hz range. Specifically, long-range, posterior-frontal connectivity with be assessed.

Secondary Outcome Measures

Name	Time	Method
Immediate and lasting reductions in anxious arousal	Immediately before, immediately after, 30 minutes after stimulation on the first and final day. Immediately before (24 hours after most recent stimulation) and immediately after stimulation on the second and third days.	Self-report ratings of subjective units of anxious arousal are acquired using a visual analog scale, ranging from 0 (not at all anxiously aroused) to 100 (extremely anxiously aroused).
Immediate and lasting changes in affective perception of sensory stimuli	Immediately before, immediately after, and 30 minutes after stimulation on the first day. Immediately before (24 hours after most recent stimulation), immediately after, and 30 minutes after stimulation on the final (fourth) day.	Pleasantness ratings of neutral and negative olfactory and auditory stimuli are acquired on a visual analog scale, ranging from 0 (extremely unpleasant) to 100 (extremely pleasant). Auditory stimuli consist of a simple tone (neutral) and scream (negative) at three different intensities (quiet, medium, and loud), each presented once for 2 seconds through headphones. Olfactory stimuli consist of a neutral odor (acetophenone) and negative odor (burning rubber), diluted in mineral oil for three different intensities (weak, medium, strong). Approximately 3 mL of each odor are presented in 30 mL amber bottles, upon which participants are asked to take one steady sniff.