40 Hz versus sham over five days in prolonged unresponsiveness
Q: What did five days of 40 Hz current change in consciousness?
A: In a 2026 randomized sham-controlled trial, five days of 40 Hz high-definition current improved coma recovery scores more than 4 Hz or sham, especially vision and arousal. At six months, 37.5% of the 40 Hz group had a good outcome, higher than the sham group (P = 0.019).
Who was in the trial
Sixty people with prolonged disorders of consciousness were randomized into four groups. One group received 40 Hz high-definition current, one received 4 Hz high-definition current, and each of those had a matching sham group. The paper is in NeuroImage, 1 November 2026.
What five days compared
The paper's main comparison is five days of 40 Hz high-definition transcranial alternating current stimulation against 4 Hz and against sham. Behavior was scored on the Coma Recovery Scale-Revised, with particular change in vision and arousal. The team also measured brain-network connectivity, and they looked at a baseline 40 Hz auditory steady-state response as a clue to who would respond.
What changed
40 Hz brought a greater improvement on the coma recovery scale than 4 Hz or sham, especially in visual and arousal scores. Short-range and long-range connectivity grew stronger, and those network changes tracked the behavior gains. A stronger baseline auditory steady-state response predicted who improved. At six months, 37.5% of the 40 Hz patients had a good outcome, a Glasgow Outcome Scale-Extended score of 4 or higher. That share was higher than in the sham group (P = 0.019).
If you want that same number in a quiet sitting, open 40 Hz in the library and sit with the headphones or the coil. The hospital used scalp current, not a KYMA device, so the sitting is the stored tone, not a copy of the trial.
The paper
Hu and colleagues, NeuroImage, 1 November 2026. PMID 42829016.
The NeuroImage record for this trial.
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| Result | What the paper reported |
|---|---|
| Coma recovery scale | Greater improvement with 40 Hz than with 4 Hz or sham, especially vision and arousal |
| Brain network | Stronger short-range and long-range connectivity that tracked the behavior gains |
| Six months | 37.5% of the 40 Hz group reached a good outcome, higher than sham (P = 0.019) |
Related tones in the KYMA library
Open these library sets if you want a stored program for the same topic. They are here because they already store 40 Hz, the number used in this trial. The hospital current strength is not stored in the tone.
40 Hz frequency promotes cognitive function, enhances neural connectivity, and supports mental clarity and focus for overall brain health. · 5 minutes
Primary gamma frequency researched by MIT for Alzheimer's and brain health (PMC6547462). Promotes neuroplasticity, memory consolidation, and immune response in the brain. · 20 min
Frequently asked questions
What did five days of 40 Hz current change?
Five days of 40 Hz high-definition current produced a greater improvement on the coma recovery scale than 4 Hz or sham, especially in visual and arousal scores. At six months, 37.5% of the 40 Hz patients had a good outcome, higher than the sham group (P = 0.019).
How did 40 Hz compare with 4 Hz?
The 40 Hz group improved more on the coma recovery scale than the 4 Hz group. Network connectivity also grew stronger with 40 Hz, and those changes tracked the behavior gains. The paper reports the 40 Hz result as greater than both 4 Hz and sham.
Which library sets already store 40 Hz?
Open 40 Hz and 40 Hz Gamma - Brain Health. Both already store 40 Hz, the same number used in this five-day trial, which is why they are the sets on this page. 40 Hz Gamma - Brain Health matches the brain topic. The current strength is not in the tone. This trial did not test these library rows.