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Despite major advances in neuroscience, many mechanisms of brain function remain unclear. Scientists are therefore developing new methods to understand better how the brain works. One such approach is non-invasive brain stimulation, which is used in both research and clinical settings. Among the most widely used techniques is transcranial direct current stimulation (tDCS).

This is a relatively simple and safe method in which electrodes are placed on the scalp. A weak electric current is applied, a small portion of which passes through the skull into the brain," explains Martin Marko from the Institute of Normal and Pathological Physiology, Centre of Experimental Medicine, SAS.The current used is very low, typically around 1 to 2 milliamperes. "This level is safe and is usually perceived only as a mild tingling, prickling, or warmth on the skin, which quickly subsides," he adds.

The electric current influences the brain's natural activity, not by directly triggering neurons, but by altering their excitability, in other words, how likely they are to respond to incoming signals. "In practice, this means that certain brain regions become slightly more or less 'ready' to react. These effects are generally mild and short-lived, typically lasting from several minutes up to about an hour after stimulation," Marko explains.

A tool for studying the mind

This ability makes tDCS a valuable tool in experimental psychology and cognitive neuroscience. Researchers can target specific brain regions, for example, those involved in attention, memory, or language, and observe how performance changes during controlled tasks. According to Marko, this approach helps scientists test hypotheses about which brain areas are involved in particular cognitive functions and how different neural systems interact.

Clinical potential

Beyond basic research, tDCS is also being explored in clinical neuroscience. In some neurological and psychiatric conditions, certain brain regions exhibit altered activity compared to those of healthy individuals. Their communication may also be disrupted. Non-invasive stimulation can help modulate this activity and may contribute to alleviating some symptoms," says Marko. There is also growing evidence that tDCS can enhance neuroplasticity, the brain's ability to adapt and reorganise its connections. "This is particularly important when stimulation is combined with rehabilitation, cognitive training, or psychotherapy, which aim to strengthen beneficial changes in brain networks," the scientist gives examples.

Despite its promise, the method has limitations. Its effects are typically subtle and can vary considerably between individuals and experimental conditions. "The outcome depends on many factors, including electrode placement, stimulation intensity and duration, the current state of the brain, and the type of task being performed," Marko explains. Current research, therefore, focuses on identifying optimal stimulation protocols that enable more precise and reliable modulation of brain activity. The goal is to understand better when and how this technique can be most effective, both for studying brain function and for developing new treatment approaches for neurological and psychiatric disorders. "Direct current stimulation may become an important tool not only for understanding the brain, but also for improving its treatment," concludes Martin Marko.

Source: Martin Marko, Centre of Experimental Medicine, SAS

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