16 Apr 2021

Can electric current spark better memory in people with mild cognitive impairment? Possibly, according to researchers—at least short-term.

At the 15th International Conference on Alzheimer's and Parkinson's Diseases, held virtually March 9–14,

, University of Brescia, Italy, presented results from a neuromodulation pilot study.

The complete findings were published in the March 21 Brain Stimulation.

He and other researchers led by Barbara Borroni at U Brescia used transcranial alternating current stimulation (tACS), a low-intensity electric current therapy set at a gamma frequency of 40 Hz.

•  After a one-hour session, people with MCI recalled more words and matched more names to faces than people who got sham treatment.

•  Their acetylcholine signaling was restored to levels seen in healthy people, the scientists claimed. Whether gamma entrainment occurred will be tested in a larger trial.

•  Participants treated with tACS remembered 25 percent more words immediately, and twice as many after the 20-minute delay, than did controls.

 While participants were completing their last 20 minutes of treatment, they completed the face-name association task. People who got active treatment also remembered almost twice as many face-name pairs. “We were astonished to see clinical and neurophysiological changes after only one hour of stimulation,” Benussi said.

Crisscross. Participants received both tACS and sham treatment, separated by a week. They were evaluated with transcranial magnetic stimulation (TMS) and took the Rey auditory verbal learning test (RAVLT) before and after each session. During the last 20 minutes of treatment, participants matched faces to names. [Courtesy of Benussi et al., 2021.]

 * * *

 This neurophysiological approach to therapy is similar, but not identical, to GENUS, which uses the sensory stimuli light and sound to coordinate neuronal firing via gamma entrainment (see Part 13 of this series).

 tACS stimulates specific brain areas with electrical current through electrodes on the scalp.

 Pulsing electricity at 40 Hz is thought to entrain gamma waves (reviewed by Strüber and Herrmann, 2020). Neuronal firing in the gamma band falls out of sync in people with MCI and Alzheimer’s disease (Koenig et al., 2005; Dec 2016 news). 

Previously, other researchers had used tACS in cognitively normal older people to stimulate 4–8 Hz theta waves in the frontotemporal cortex. This synchronized participants' natural theta oscillations within 25 minutes of treatment, which in turn improved their working memory for at least 50 minutes afterward (Apr 2019 news).

https://www.alzforum.org/news/conference-coverage/pilot-study-electric-therapy-improves-memory

In at Red, Out at Black. During transcranial alternating current stimulation, low-intensity 40 Hz electricity flows from one electrode (red) to the other (black). The current is believed to travel through the precuneus deeply into the brain and out to the shoulder. [Courtesy of Benussi et al., 2021.]

• “We were astonished to see clinical and neurophysiological changes after only one hour of stimulation,” Benussi said.

•   At the clinic, participants wore the tACS device for one hour.

  It emitted 40 Hz electric current for the entire hour during active treatment -

 and for one minute during sham treatment.

 “After one minute, people cannot feel the current anymore, so they cannot tell if they receive pulses for longer,”

 Benussi wrote to Alzforum.

 All 20 participants completed the trial; none reported significant side effects.

For the GammAD pilot study, Benussi and colleagues recruited 20 people with mild AD from the Center for Neurodegenerative Disorders in Brescia. The researchers stuck one electrode to the top of each participant’s scalp and the other to his or her right shoulder (see image below).

 “Current flows from one to the other, so the second electrode guides the current from the skull through deep brain structures, such as the precuneus,” Benussi explained. They targeted the precuneus, an area in the default network, because amyloid plaques accumulate there early in AD (Aug 2009 news).

 People who got active treatment also remembered almost twice as many face-name pairs. “We were astonished to see clinical and neurophysiological changes after only one hour of stimulation,” Benussi said.