Short-term effects of rhythmic sensory stimulation in Alzheimer’s disease

Alzheimer’s disease (AD) is the most common type of dementia. Coherent neural oscillations with a resultant frequency of 40 Hz (40 Hz oscillation) seem to play an important role in maintaining the correct stream of consciousness. In turn, people with AD may have this parameter underestimated. Moreover, it was noted that auditory stimulation in healthy people can reset the 40 Hz oscillation. Therefore, the goal of the Canadian researchers was to test whether whole-body sound-controlled rhythmic sensory stimulation (RSS) with a frequency of 40 Hz could increase the steady-state 40 Hz oscillation in AD patients and whether cognitive function could be improved this way.

• 40 Hz RSS therapy improved the mental functions of people with AD.
• It had the greatest effect in patients with mild and moderate AD symptoms.

Prepared on the basis of:

Short-Term Effects of Rhythmic Sensory Stimulation in Alzheimer’s Disease: An Exploratory Pilot Study. Clements-Cortes A, Ahonen H, Evans M et al. J Alzheimers Dis. 2016 Mar 25;52(2):651-60.

Study population

10 men and 8 women (59-93 years old) diagnosed with AD (6 mild, 6 moderate or 6 severe cases) were studied.

Test procedure

Each participant received 12 treatment sessions: 6 sessions of rhythmic sensory stimulation (RSS) – whole body sound vibrations at 40 Hz – or, for comparison, 6 sessions of visual stimulation. Except that the participants were randomly divided into 2 groups in an alternating pattern. The first group received 6 sessions of visual stimulation first, followed by 6 sessions of 40 Hz RSS, while the second group received 6 sessions of 40 Hz RSS first and then 6 sessions of visual stimulation. There was a 2-day break after the first 6 sessions. Therapeutic sessions (35-40 minutes each) were held twice a week for 6 weeks. Therapeutic stimuli were presented during each session for 30 minutes.

The 40 Hz RSS methodology is outlined in the next chapter.

During visual stimulation, participants sat in the inactive NextWave chair (which was only active during the 40 Hz RSS therapy, see below) and watched visual stimuli – images of nature, ocean waves – special videos for AD therapy on a TV screen.

Before the initiation of therapy and after 12 therapeutic sessions, among others, St. Louis University Mental Status test (SLUMS) results were analyzed.

Use of vibration in the study

RSS 40 Hz is a treatment technique based on the stimulation of neuromuscular and circulatory activity with low-frequency sound. It was administered using the NextWave chair, a medically recognized somatosensory vibroacoustic stimulation device. NextWave produces low-frequency sound waves (27-113 Hz) that provide whole-body vibro-tactile stimulation.

To avoid the effect of desensitizing the mechanoreceptors, the vibration frequency of the 30-minute 40 Hz RSS treatment was changed smoothly over a repeating 2.3-second cycle with a frequency of 39.96 Hz to 40.06 Hz.

Results

There were no significant changes in the SLUMS results after visual stimulation, while the SLUMS test improved after 40 Hz RSS.

40 Hz RSS therapy was found to have the strongest effect in patients with mild to moderate AD symptoms.

Comment

The results of this pilot study are promising and therefore further research into a potential novel therapy for AD – 40 Hz RSS – is required. This therapy can improve cognitive function over time.

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