Summary: A new study shows that transcranial direct current stimulation (tDCS), a non-invasive brain stimulation method, can influence how quickly and flexibly people make decisions. Researchers targeted the dorsolateral prefrontal cortex—key in planning and action—while participants performed simultaneous visual and auditory tasks.
Anodal stimulation, which enhances brain activity, led to quicker decisions, while cathodal stimulation, which suppresses activity, made participants stick to previous choices. Though subtle, these results suggest tDCS may modulate cognitive flexibility under specific conditions.
Key Facts:
- Targeted Brain Area: Stimulation focused on the dorsolateral prefrontal cortex, which regulates planning and decision-making.
- Effect on Flexibility: Anodal stimulation sped up task choices, while cathodal stimulation reduced adaptability.
- Cognitive Impact: Changes were subtle (~100ms) but statistically significant in experimental psychology.
Source: Martin Luther University Halle-Wittenberg
A simple method of brain stimulation has been shown to change how people make decisions.
These were the findings of a new study by the Martin Luther University Halle-Wittenberg (MLU), which was published in the Journal of Cognitive Neuroscience.
The investigation used transcranial direct current stimulation, which is an established method in research and therapy.
In transcranial direct current stimulation, a very weak electric current flows through electrodes that have been placed on the scalp. This can be used to activate or inhibit specific regions of the brain.
In anodal stimulation, a positive electrode is applied, which increases the activity of the nerve cells. In contrast, cathodal stimulation uses a negative electrode and inhibits activity.
“The method has great advantages as it is non-invasive and very easy to use. This is why it is widely utilised in psychology,” says Dr Sebastian Kübler, a psychologist at MLU. Its potential use in treating neurological and mental disorders is also being intensively investigated.
The scientists at MLU are studying whether direct current stimulation influences how people make decisions. In the study, which included 40 study participants, a specific region of the brain called the dorsolateral prefrontal cortex was stimulated.
“The region is crucial for planning and weighing up actions,” explains Torsten Schubert, a professor at the Institute of Psychology at MLU.
The participants had to complete two tasks at the same time – an auditory and a visual task – and had to decide which one they would solve first. The test subjects wore the electrodes throughout the entire experiment.
However, at the time of the study, neither they nor the researchers knew what type of stimulation was being used or whether any current was flowing at all. The experiments were repeated at intervals of at least one week.
The study found that with anodal stimulation, which increased the activity in the region of the brain, the participants needed less time overall to choose the task; in other words, the decision was made more quickly.
When cathodal stimulation was applied, which inhibits brain activity, participants tended to stick with a previously chosen order.
“This suggests that an activated or inhibited dorsolateral prefrontal cortex increases or reduces cognitive flexibility when people have to perform several tasks simultaneously,” says Sebastian Kübler.
The difference was found to be in the range of around 100 milliseconds.
“This seems small at first, but in experimental psychology it is a relevant change. It appears that transcranial direct current stimulation changes a person’s ability to decide which action to take,” explains Torsten Schubert.
Devices that use transcranial direct current stimulation are now even being sold commercially and are touted as being able to increase creativity and concentration.
“Such sweeping promises are not credible. However, our study does show that the method can, under controlled conditions, influence cognitive processes such as decision-making. It should also be noted that the effects are very subtle and depend on many factors,” says Kübler.
About this brain stimulation and decision-making research news
Author: Tom Leonhardt
Source: Martin-Luther-Universität Halle-Wittenberg
Contact: Tom Leonhardt – Martin-Luther-Universität Halle-Wittenberg
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Voluntary Task-order Coordination in Dual-task Situations” by Sebastian Kübler et al. Journal of Cognitive Neuroscience
Abstract
Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Voluntary Task-order Coordination in Dual-task Situations
Dual tasks (DTs) require additional control processes that temporally coordinate the processing of the two component tasks.
Previous studies employing imaging as well as noninvasive stimulation techniques have demonstrated that the dorsolateral prefrontal cortex (dlPFC) is causally involved in these task-order coordination processes.
However, in these studies, participants were instructed to match their processing order to an externally provided and mandatory order criterion during DT processing.
Hence, it is still unknown whether the dlPFC is also recruited for rather voluntary order control processes, which are required in situations that allow for intentional and internally generated order choices.
To address this issue, in two experiments, we applied anodal (Experiment 1) and cathodal (Experiment 2) transcranial direct current stimulation during a random-order DT in which participants could freely decide about their order of task processing.
In our results, we found facilitatory and inhibitory effects on voluntary task-order coordination because of anodal and cathodal transcranial direct current stimulation, respectively.
This was indicated by shorter RTs when participants intentionally switched the task order relative to the preceding trial during anodal as well as a reduced tendency to switch the task order relative to the preceding trial during cathodal stimulation compared with the sham stimulation.
Overall, these findings indicate that the dlPFC is also causally involved in voluntary task-order coordination processes.
In particular, we argue that the dlPFC is recruited for intentionally updating and implementing task-order information that is necessary for scheduling the processing of two temporally overlapping tasks.
