Health · Medical Research · 2 hrs ago
Brain stimulation improved test performance but increased mental fatigue
Researchers stimulated a brain region linked to mental effort in a study of 31 healthy volunteers.
The volunteers did a demanding memory test while electrodes delivered a mild electrical current to the dorsolateral prefrontal cortex in some participants.
Those who received stimulation responded faster and more accurately than participants who received sham stimulation.
Afterward, they were less likely to choose a harder test for a higher payment, suggesting better performance came with greater mental fatigue.
The stimulated volunteers also had higher levels of glutamate in the targeted brain region, but the study did not show that glutamate caused the fatigue.
Researchers say the findings support taking breaks when mentally tired, though it remains unclear whether stimulation improves productivity over a full workday.
Future studies could examine the brain region’s role in conditions such as depression that affect motivation.
Electrical stimulation of a brain region linked to mental effort improved volunteers’ performance on a demanding memory test.
The stimulation was also followed by greater mental fatigue and lower motivation to choose a harder task.
The study involved 31 volunteers and targeted the dorsolateral prefrontal cortex using transcranial direct current stimulation.
Researchers measured higher glutamate levels in that brain region after stimulation, but the study did not establish that glutamate caused the fatigue.
Experts said the findings do not show that stimulation would improve productivity over a working day.
- Who
- Researchers led by Hongmei Xia at the University of Munich studied 31 volunteers with no known health conditions.
- What
- Electrical stimulation of the dorsolateral prefrontal cortex improved performance on a difficult memory test but was associated with more mental fatigue.
- When
- The article was published on 2026-11-02. The study session lasted half an hour.
- Where
- The volunteers took part in a session in an MRI scanner.
- Why
- The researchers investigated how stimulating a brain region involved in controlling mental effort affected task performance and motivation.
Hongmei Xia
Emile Radyte and Nilli Lavie
Meaning of the findings
Hongmei Xia
Xia said the results were strong evidence that stimulation improved performance at the cost of lower motivation and greater fatigue.
Emile Radyte and Nilli Lavie
Radyte said the study did not prove that glutamate caused the fatigue, while Lavie said fatigue could result from using more neural energy.
Practical benefit
Hongmei Xia
Xia said she could imagine stimulation improving performance on cognitive tasks, although people might feel more fatigued afterwards.
Emile Radyte and Nilli Lavie
Radyte said a short laboratory task does not establish a productivity benefit over a working day, and Lavie noted that precisely targeting the brain region is difficult without MRI guidance.
Volunteers spent 20 minutes taking a 3-back memory test while some received electrical stimulation to the dorsolateral prefrontal cortex.
Researchers measured glutamate levels in the stimulated brain region and found higher levels among volunteers who had received stimulation.
New Scientist published its report on the study.
- Participants
- 31 volunteers with no known health conditions
- Stimulation
- Transcranial direct current stimulation, or tDCS
- Target
- Dorsolateral prefrontal cortex
- Average reaction time
- 0.98 seconds with stimulation; 1.12 seconds with sham stimulation
- Task choices
- €1 for an easy test or €2 for a harder one
What people are saying
Their performance is much better; however, this good performance comes with lower motivation in the end
A 20-minute laboratory task does not establish a net productivity benefit over a working day
Drink coffee instead.