A recent clinical trial published in the open-access journal General Psychiatry suggests that twice daily non-invasive electrical stimulation of the brain may enhance cognitive function in individuals with Alzheimer’s disease. The trial investigated the use of transcranial direct current stimulation (tDCS), a technology that can potentially establish new neural networks by firing up the brain’s plasticity.
tDCS utilizes a device with two electrodes placed over specific areas of the head. These electrodes deliver a constant low-intensity electrical current. Apart from treating depression, tDCS is now being explored in various medical fields.
The objective of the trial was to determine if tDCS could improve cognitive function in individuals with Alzheimer’s disease and whether this improvement was linked to the restoration of cortical plasticity, which refers to the brain’s ability to form new neural networks.
A total of 140 participants diagnosed with mild to moderate Alzheimer’s disease from four different hospitals were randomly assigned to receive either two daily sessions of active (constant low-intensity 1-2 mA current) or sham tDCS for a period of up to six weeks, five days a week.
The electrical stimulation was applied to the prefrontal cortex, which plays a role in higher-order activities such as planning, decision-making, working memory, social behavior moderation, and certain aspects of speech and language.
All participants were over 65 years old, had been diagnosed with Alzheimer’s disease for more than six months, and had scored below 26 on the Mini-Mental State Exam (MMSE), indicating cognitive impairment. The baseline characteristics, including age, sex, and educational attainment, were similar in both groups.
Cognitive performance was assessed using the MMSE and the Alzheimer’s Disease Assessment Scale-Cognitive (ADAS-Cog) Test at the beginning of the trial, after two weeks, and again after six weeks. Changes in neural plasticity were measured by analyzing electrical signaling in the motor pathways through a process called motor evoked potential (MEP).
Out of the participants, 133 completed the two-week intervention, and 124 completed the six-week intervention. Withdrawals occurred for various reasons, but discomfort did not contribute to the decision to withdraw.
After two weeks, no significant changes were observed in either group. However, compared to baseline, the tDCS group displayed substantial improvement in cognitive function, especially in word recall, recall of test instructions, and word recognition, following 30 sessions of 20-minute tDCS. No such improvements were observed in the sham group.
Furthermore, the results indicated that cortical plasticity, which was impaired in people with Alzheimer’s disease, improved after six weeks of tDCS treatment. As MEP decreased, word recall and word recognition improved significantly in the tDCS group, but not in the sham group, suggesting that the degree of cognitive improvement correlated with the improvement in cortical plasticity.
The precise mechanism of action for tDCS is not clearly understood. Previous research has suggested that tDCS may alter ion activity, neurotransmitter release, and electrical activity in different regions of the brain.
The researchers acknowledge several limitations to their findings, such as the small size of the study, the absence of MRI or electroencephalography scans to track changes in brain structure, and the lack of cerebrospinal fluid and blood samples to monitor neurotransmitter changes.
Despite these limitations, the researchers conclude that the results of the study strongly indicate that tDCS treatment holds significant promise as an intervention for improving cognitive function in individuals with Alzheimer’s disease. Furthermore, they emphasize the crucial role of plasticity in cognitive change.
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1. Source: Coherent Market Insights, Public sources, Desk research
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