Brain region temporarily stimulated for cognitive improvement

A new study suggests that temporarily zapping a specific area of the brain can improve performance on mentally demanding tasks, but at a cost to motivation and energy levels.

Researchers led by Hongmei Xia from the University of Munich in Germany used transcranial direct current stimulation (tDCS) to stimulate the dorsolateral prefrontal cortex, an area linked to motivation and mental effort. The volunteers were unaware they were receiving the treatment, which was delivered through electrodes placed on their heads during a half-hour session in an MRI scanner.

During this time, the participants completed a 3-back memory test, where they had to remember and identify the third item back as an ongoing sequence of numbers or letters was presented. This task requires significant mental effort and is often used to assess working memory capacity. The volunteers who received tDCS performed significantly better on the test than those who did not receive the treatment.

However, the improved performance came at a cost: these same volunteers showed lower motivation in completing subsequent tasks, suggesting that the temporary boost to cognitive function was offset by increased mental fatigue.

The brain region involved in controlling cognitive effort has been identified by researchers as the dorsolateral prefrontal cortex. This area is responsible for helping individuals to work hard and maintain focus.

Studies have shown that stimulating this region can improve cognitive performance, with one recent study using transcranial direct current stimulation (tDCS) on volunteers achieving faster reaction times and higher accuracy rates compared to those who did not receive the treatment. The results suggested that even a brief period of tDCS could have a significant impact.

However, the benefits of this type of stimulation come at a cost, with research indicating that it can lead to increased mental fatigue. This is thought to be due in part to an accumulation of glutamate in the brain, which can harm cells if levels become too high.

Levels of glutamate were found to be higher in volunteers who received tDCS compared to those who did not, particularly in the dorsolateral prefrontal cortex.

Neuroscientist Emile Radyte from Samphire Neuroscience believes that transcranial direct current stimulation (tDCS) can enhance productivity in individuals affected by conditions like premenstrual syndrome. According to her trials, applying tDCS over the dorsolateral prefrontal cortex can help restore productivity hindered by such conditions.

However, Radyte is cautious about using tDCS as a means to boost mental performance, pointing out that a 20-minute laboratory task may not accurately reflect its long-term benefits. She suggests that more research is needed to establish the net productivity gain of using tDCS in everyday work settings.

Nilli Lavie from University College London praises the study but raises concerns about the potential drawbacks of using tDCS. She notes that increased mental fatigue could be a result of heightened neural activity rather than excessive glutamate buildup, which was observed in volunteers who received tDCS.

Lavie also points out that accurately targeting the dorsolateral prefrontal cortex with tDCS can be challenging without the aid of an MRI scanner to guide the procedure. In response to these concerns, she jokingly recommends a more conventional approach: "Drink coffee instead."