On June 13 at 12:15 Jaan Tulviste will defend his doctoral thesis "Modulation of decision-making by transcranial magnetic stimulation".
Professor Talis Bachmann, University of Tartu
Professor Henry Railo, University of Turku, Finland
Human decision-making is known to depend on the prefrontal cortex and distal areas interconnected to it, but its specific neurobiological mechanisms are still largely unknown. Expanding our knowledge of decision-making processes contributes to understanding the neuropsychological principles of executive function and goal directed behaviour, as well as to advancing the clinical application of neurostimulation in this domain. Within empirical studies included in the current dissertation, repeated transcranial magnetic stimulation (rTMS) was applied to the dorsolateral prefrontal cortex (DLPFC) in order to evaluate potential effects on performance across various decision-making tasks. By observing how non-invasive modulation of neural activity in underlying cortical areas affects non-veridical cognition related behavioural choices, the thesis addressed the functional role of the DLPFC in decision-making processes. Results of Study I demonstrated that non-veridical and veridical decision-making both rely on the right DLPFC, whereas the left DLPFC is more specifically committed to non-veridical cognition. Study I findings also emphasised non-focal, distal effects of TMS, when applied to particularly richly interconnected cortical regions such as the DLPFC. Study II revealed that TMS-induced inhibition of the right DLPFC activity affects non-veridical risky behaviour, suggesting that the right DLPFC plays a role in execution and monitoring of performance in risky tasks with a motor response. Study III revealed that non-veridical behaviour is influenced by genetic differences related to the BDNF gene and that TMS stimulation enhances pre-existing genetically determined biases in decision-making preferences. In conclusion, decision-making behaviour can be modulated by applying TMS to the DLPFC, but the resulting behavioural effects depend on the characteristics of the task, the lateralization of task-specific cognitive mechanisms, as well as the neurobiological endophenotypes involved.