Sağ pre-SMA rTMS'nin iki alternatifli algısal karar vermedeki hız-zaman ödünleşimine etkileri

The decision processes in two-alternative scenarios can be explained by the drift-diffusion model. According to this model, a decision variable moves towards one of two decision boundaries corresponding to the two alternatives based on the evidence accumulated in favor of these options and a decision is made when one of the decision boundaries is hit. However, the noise in the evidence accumulation process creates randomness in the trajectory of the decision variable which might result in hitting the wrong decision boundary. This leads to the speed-accuracy tradeoff (SAT) which is modulated by how high the decision boundaries are set. While higher threshold setting increases the likelihood of an accurate decision at the cost of longer response times, lower threshold setting results in less accurate but faster decisions. Recent neuroimaging studies showed that the activity of pre-supplementary motor area (pre-SMA) and striatum was higher when speed was emphasized compared to when accuracy was emphasized. Additionally, the activity in these brain regions was negatively linked with decision thresholds. However, the imaging studies provide only correlational information. In the current study, we aimed to draw a causal relationship between the pre-SMA activity and threshold setting by inhibiting the activity in this region using rTMS. Participants performed random dot motion task after pre-SMA or vertex (control condition) inhibition and decision thresholds for both rTMS sessions were estimated by the drift diffusion model. Our results revealed that under the pre-SMA inhibition condition, participants set higher decision thresholds and exhibited more cautious decisions compared to the control condition. Furthermore, the weight assigned to accuracy relative to reward was higher under the pre-SMA inhibition condition. Additionally, while the decision thresholds in the post-error trials were higher compared to the post-correct trials, this change did not differ between the conditions.