The Role of Inhibition and its Neural Substrate in Decision-Making: A Transcranial Magnetic Stimulation Study

A vital aspect of daily life in our uncertain world is to make decisions, which are often accompanied by the capacity to inhibit those that are inadequate. Inhibition supports this process by controlling our main responses and suppressing irrelevant information that interferes with decision-making (DM). There are three main cortical brain areas involved in DM: The right inferior frontal gyrus (rIFG), the pre-supplementary motor area (pre-SMA), and the primary motor cortex (M1). However, it is unclear which of the various pathways linking these regions and the subcortical areas involved are crucial for inhibitory control. Thus, the present research aimed to investigate the causality of the brain areas involved in this network using continuous theta burst stimulation (cTBS) in healthy participants. A total of 17 healthy individuals (11 females) with a mean age of M = 25.12 (SD = 4.40), ranging from 20 to 35 years, underwent three randomized sessions of cTBS applied over rIFG, pre-SMA, and sham stimulation to the vertex. Participants completed the TMS health and safety checklist before each session and a series of questionnaires (e.g., STAI, Barratt BIS-11, etc.). Before receiving the cTBS condition, subjects performed a stop-signal task and after the stimulation, they completed the two versions of a multiattribute probabilistic inference task in a counterbalanced order (PIT; compensatory [C] and noncompensatory [NC] task structure). The preliminary results indicate that regardless of the structure of the task, the heuristic Take-the-Best (TTB) was a better strategy than the weighted additive rule (WADD) for describing the inferences of the participants. Regarding the effects of cTBS, inhibiting rIFG did not produce any significant effect on participants’ relative strategy preference (RSP) compared to sham. On the contrary, inhibiting pre-SMA led to a significant decrease in the RSP of TBB over WADD in the block trial where the proportion of discriminatory trials was the highest. Although our study lacks the power analysis needed to draw reliable conclusions, the results suggest that the rIFG may function as a hub that hosts functional networks other than only inhibition, while the effects of inhibiting pre-SMA may indicate that it functions as a modulatory center of decision thresholds. More studies are needed in the convergence of multiattribute decision-making with TMS to better understand the causal role of the cortical and subcortical areas involved in inhibitory control.