Activation of the DLPFC Reveals an Asymmetric Effect in Risky Decision Making: Evidence from a tDCS Study

Abstract

The phenomenon of loss aversion (the tendency for losses to have a greater impact than comparable gains) has long been observed in daily life. Neurocognitive studies and brain imaging studies have shed light on the correlation between the phenomenon of loss aversion and the brain region of the prefrontal cortex. Recent brain stimulation studies using bilateral transcranial magnetic stimulation or transcranial direct current stimulation (tDCS) have obtained various results showing the causal relationship between brain regions and decision making. With the goal of studying whether unilateral stimulation can change participants' risky decision making in the frames of gains and losses, we applied different polarities of tDCS over the regions of the right or left prefrontal cortex. We also designed a risk measurement table (Multiple Price List) to reflect the participants' attitudes toward risky decision making via the crossover point including the frames of gains and losses. The results of our experiment indicated that the participants tended to be more risk averse in the gain frame after receiving left anodal tDCS and more risk seeking in the loss frame after receiving right cathodal tDCS, which was consistent with the hypothesis that the process of risky decision making was correlated with the interaction of multiple systems in the brain. Our conclusion revealed an asymmetric effect of right/left DLPFC when the participants faced gains and losses, which partially provided the neural evidence and a feasible paradigm to help better understand risky decision making and loss aversion. The current study can not only expand the traditional understanding of the behavioral preferences of humans in economics but also accommodate empirical observations of behavioral economists on the preferences of humans.

Keywords: asymmetric effect; dorsolateral prefrontal cortex; loss aversion; risk preference; transcranial direct current stimulation.

FIGURE 1

Schematic and locations of the electrode positions. Schematic of the electrode positions based on the EEG 10–20 system (A) and locations of the dorsolateral prefrontal cortex and the parietal cortex of the human brain (B).

FIGURE 2

The stimulation modes of the four active treatments. The axis of this electronic potential diagram represents the input voltage of tDCS device, ranging from -18.476 V to 14.463 V. The deeper color represents the higher voltage and stronger current.

FIGURE 3

Schematic representation of the experimental design.

FIGURE 4

The estimated marginal means of crossover points in both frames.

FIGURE 5

The crossover points in the gain frame (A) and the loss frame (B). The error bars indicate 95% confidence intervals. The asterisks indicate statistical significance of differences between treatments.