Continuous theta burst stimulation of right dorsolateral prefrontal cortex induces changes in impulsivity level

Abstract

There is evidence that the right dorsolateral prefrontal cortex (DLPFC) may play a certain role in decision making related to reward value and time perception and, in particular, in the inhibitory control of impulsive decision making. Using the theta burst stimulation (TBS) and a delay discounting (DD) task, we investigated the potential role of right DLPFC in impulsive decision making defined by the rate of discounting delayed reward. Healthy right-handed volunteers underwent three stimulation sessions, intermittent TBS (iTBS), continuous TBS (cTBS), and sham. The steepness of the discount function (k-value), reaction time for choice and consistency were measured for each subjects. cTBS of the DLPFC reduced by 36.88 % the k-value of the DD task compared to sham condition. In contrast, iTBS did not affect impulsivity level. There were no changes neither in reaction time for choice nor consistency after either the iTBS or cTBS compared with the sham stimulation. These results demonstrate that cTBS-induced modulation of cortical excitability of the right DLPFC may affect and reduce impulsive decision making. These observations may provide some insights into the role of the right DLPFC in modulating impulsivity level and calculating reward value at different time scales under less ambiguous circumstances.

Copyright 2010 Elsevier Inc. All rights reserved.

Figures

Figure 1

Display of the research procedure.

Figure 2

Visual display and timing of trials for delay discounting (DD) task.

Figure 3

Mean total k-value for the each theta burst stimulation (TBS) conditions. Error bars represent the standard errors of the mean. *P < .05 using a nonparametric Freedman test. †P < .05 using a nonparametric Wilcoxon signed rank test.

Figure 4

Mean reaction time (A) and consistency for response choice (B) in each theta burst stimulation (TBS) condition. Error bars represent the standard errors of the mean.