Abstract
Many perceptual decisions are inevitably subject to the tradeoff between speed and accuracy of choices (SAT). Sequential sampling models attribute this ubiquitous relation to random noise in the sensory evidence accumulation process, and assume that SAT is adaptively modulated by altering the decision thresholds at which the level of integrated evidence should reach for making a choice. Although, neuroimaging studies have shown a relationship between right presupplementary motor area (pre-SMA) activity and threshold setting, only a limited number of brain stimulation studies aimed at establishing the causal link, results of which were inconsistent. Additionally, these studies were limited in scope as they only examined the effect of pre-SMA activity unidirectionally through experimentally inhibiting the neural activity in this region. The current study aims to investigate the predictions of the striatal theory of SAT by experimentally assessing the modulatory effect of right pre-SMA on threshold setting bi-directionally. To this end, we applied both offline inhibition and excitation to the right pre-SMA utilizing transcranial magnetic stimulation in a within-subjects design and tested participants on a Random Dot Motion Task. Decision thresholds were estimated using the Hierarchical Drift Diffusion Model. Findings of our planned comparisons showed that right pre-SMA inhibition leads to significantly higher, whereas right pre-SMA excitation leads to significantly lower thresholds without showing any effects on the evidence integration process itself.
•Speed-accuracy tradeoff is modulated by decision-threshold modulation.•Cortico-striatal network is implicated in adaptive speed-accuracy tradeoff.•Inhibition of right pre-SMA leads to higher (accuracy emphasis) decision thresholds.•Excitation of right pre-SMA leads to lower (speed emphasis) decision-thresholds.•Right pre-SMA has a modulatory role in speed-accuracy tradeoff.