Can brain stimulation reduce anxiety long-term?
Repetitive rhythmic electrical stimulation of the brain's visual areas reduces anxiety and strengthens long-distance brain networks over several days.
Source
Lasting connectivity increase and anxiety reduction via transcranial alternating current stimulation
What they did
Thirty-eight healthy young adults participated in a study consisting of four sessions, each separated by 24 hours. During these sessions, participants received 30 minutes of active or fake electrical brain stimulation. Researchers measured brain activity and tracked self-reported anxious arousal levels on a scale from 0 to 100.
What they found
Active brain stimulation led to a 34% reduction in anxiety after the first session, which was maintained throughout the study. The stimulation also strengthened directional brain connections in the alpha frequency band, which naturally ranges from 8 to 12 hertz. This connectivity boost remained elevated even 24 hours after previous stimulation sessions, showing long-term benefits.
The limits
What it doesn't show
The study only looked at 38 healthy volunteers, meaning we do not know if these results apply to clinical populations. Because the sessions only lasted over four days, it is unclear if the benefits persist weeks later. Additionally, because there was no long-term follow-up after the fourth day, the researchers could not determine when the anxiety-reducing and network-strengthening effects eventually wear off.
Key terms
- tACS
- A non-invasive technique that applies low-intensity electrical currents oscillating at specific frequencies through electrodes on the scalp to modulate brain rhythms.
- Alpha oscillations
- Brain waves oscillating between 8 and 12 hertz that are prominent during restful alertness and are involved in sensory inhibition and network communication.
- Granger causality
- A statistical method used to determine the directional influence or flow of information from one brain region to another.
- Late-phase LTP
- A durable, protein-synthesis-dependent strengthening of synapses that underpins long-term memory and permanent neural plasticity.
- Default mode network
- A large-scale network of interacting brain regions that is highly active during restful waking states and self-referential thought.
- Anxious arousal
- A state of physiological and psychological tension characterized by hypervigilance, worry, and somatic symptoms of anxiety.
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How do the authors define "oscillopathies" in the context of neuropsychiatric disorders?
Common questions
Why did the brain wave power return to normal while brain connectivity remained high?
Local brain wave power is heavily regulated by deep, subcortical pacemakers that likely reset cortical alpha activity back to its natural baseline once stimulation stops. In contrast, the connections between different cortical regions rely on pathways that undergo long-term synaptic changes, which can bypass these subcortical reset mechanisms and remain strengthened over days.
Did participants know whether they were receiving the real or fake stimulation?
No, participants were successfully blinded to their condition because the researchers applied a brief ramp-up and ramp-down of electrical current during the fake stimulation, mimicking the scalp sensations of the active group.
How did the researchers measure the physical and behavioral symptoms of anxiety?
They used a visual analog scale where participants rated their subjective level of anxious arousal from 0 to 100, and they also had participants rate the pleasantness of unpleasant sounds and odors, which are highly sensitive to states of hyperarousal.
Why did the researchers target the back of the head instead of the front?
The back of the head is the primary generator of resting alpha waves, and previous research showed that people with PTSD have severe alpha wave deficits in this specific area, making it a promising target to restore natural rhythms.
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