How Brain Stimulation Affects Risky Choices
Applying 20-Hz electrical stimulation to the left prefrontal cortex increases a person's willingness to make risky financial decisions.
Source
Transcranial Alternating Current Stimulation Modulates Risky Decision Making in a Frequency-Controlled Experiment
What they did
Researchers applied transcranial alternating current stimulation (tACS) to the left or right prefrontal cortex of 34 healthy participants while they completed a specialized financial choice task. The electrical stimulation was delivered at various frequencies (5 Hz, 10 Hz, 20 Hz, 40 Hz, or a sham control) to determine if targeting specific brain oscillations could modulate choices under risk. Participants chose between safe choices with certain monetary outcomes and risky options with fluctuating gains or losses under varied conditions of task-switching.
What they found
The study demonstrated that delivering 20-Hz stimulation specifically to the left prefrontal cortex significantly increased the rate of risky decisions compared to both the sham and 40-Hz stimulation. This effect was highly frequency-specific and hemisphere-specific, as other frequencies and right-side stimulation had no notable impact on risk behavior. Overall, the participants opted for the risky options 63.6% of the time, and they exhibited slower reaction times when switching tasks or contemplating potential losses.
The limits
What it doesn't show
Because the researchers did not record brain activity during the experiment, this study cannot prove whether the stimulation actually synchronized beta-frequency brainwaves or simply modified overall cortical excitability. Additionally, the small sample size of 34 participants split into two groups limits the generalizability and statistical power of the results. Lastly, the task design only evaluated short-term behavioral choices during active stimulation, leaving it unclear if these changes in risk preference persist after the electrical currents are turned off.
Key terms
- tACS
- A non-invasive brain stimulation technique that applies low-level alternating electrical currents to the scalp to target and synchronize endogenous brain rhythms.
- Beta-activity
- A specific range of brainwave frequencies (typically 13 to 30 Hz) that are closely associated with cognitive control, motor processes, and reward anticipation.
- Dorsolateral prefrontal cortex
- A region at the front of the brain that plays a critical role in executive control, planning, and voluntary decision-making under uncertainty.
- Task-switching paradigm
- An experimental task requiring participants to rapidly alternate between different rules or instructions, used to measure cognitive flexibility.
- Entrainment
- The process by which the brain's natural electrical oscillations synchronize their phase and rhythm with an external periodic physical stimulus.
- Sham stimulation
- A control condition in research studies where a stimulator is activated briefly to mimic physical sensations but delivers no therapeutic electrical dose.
Flashcards
Want these cards to stick?
Save the deck to NoteFren and study it with spaced repetition.
Quiz yourself
What is the main frequency-specific effect of online tACS applied to the left dorsolateral prefrontal cortex (PFC) on risky decision making?
Common questions
Why did the researchers test different electrical frequencies?
They wanted to determine if modulation of risk-taking behavior is frequency-specific (meaning it is linked to a specific brainwave band like beta or theta) or if any electrical stimulation to the region would cause the same effect.
How was risk defined in this experiment?
Risk was defined as choosing a lottery with a 50% chance of winning 50 rubles (or losing 50) over a safe choice with a 100% chance of winning 25 rubles (or losing 25).
Why did the researchers target the left prefrontal cortex?
The prefrontal cortex is a core brain area involved in cognitive control, and the left hemisphere has been previously implicated in the active evaluation of risks and reward-seeking behaviors.
Did the brain stimulation degrade the participants' cognitive performance?
No, overall task performance remained highly accurate (above 92%), suggesting that the stimulation specifically altered decision preferences rather than impairing general cognitive functioning.
More on Neural oscillations