Online Rhythmic Transcranial Magnetic Stimulation Can Reveal the Precise Moment When Preferences Shift in the Human Brain

Cognitive dissonance is a complex and multifaceted psychological phenomenon that arises in challenging decision-making scenarios. Multiple regions of the brain participate in its occurrence, yet the neurodynamics of underlying cognitive mechanisms remain a subject of debate. Researchers from the HSE Institute for Cognitive Neuroscience have proposed the use of online transcranial magnetic stimulation applied to participants as they were actively engaged in tasks, to pinpoint the moment of cognitive dissonance resolution. Their findings have been published in a review paper in Frontiers in Human Neuroscience.

The study, financed by a megagrant received by the International Laboratory of Social Neurobiology, employed the unique Automated System of Non-invasive Brain Stimulation with Synchronous Registration of Bio-electrical Current in the Brain and Eye Fixation Tracking.

Every individual is faced with the need to make choices and decisions daily. Some choices are straightforward; for instance, if you clearly favour watermelons over melons, selecting your preference at the supermarket is effortless. However, there are instances when an individual must decide between equally appealing options, which makes the choice truly challenging. In such cases, cognitive dissonance can arise—a state of internal discomfort resulting from a conflict between preferences and action. To alleviate this discomfort, people tend to re-evaluate their preferences in favour of the chosen option.

For instance, a prospective student might grapple with the decision of whether to enrol at MSU or HSE. After careful consideration, they opt for one university but experience cognitive dissonance—a nagging internal conflict: what if the alternative would have been better? In order to restore their internal peace and contentment, they begin rationalising their decision and seeking confirmation that the selected university is indeed the better choice.

Alina Davydova
Author of the study, Research Assistant, HSE Institute for Cognitive Neuroscience

Previous studies have demonstrated the role of various brain regions, including both cortical areas and subcortical structures, in cognitive dissonance. However, the temporal aspects of cognitive dissonance continue to be a subject of debate. At what precise moment does a shift in preferences occur, enabling an individual to resolve cognitive dissonance: during the challenging decision-making process, immediately following the choice, or upon encountering the options again?

Neurophysiologists from the HSE Institute for Cognitive Neuroscience have suggested employing the method of online rhythmic transcranial magnetic stimulation (TMS) to monitor the dynamics of cognitive dissonance. Previous studies have only used offline stimulation.

The TMS method operates on the principle of electromagnetic induction. A coil connected to a stimulator generating magnetic fields at specific frequencies and intensities is positioned near the subject's head. TMS pulses readily penetrate the skull and meninges, altering the threshold for neuronal excitation. When the threshold is lowered, a specific brain region becomes activated; conversely, when the threshold is raised, the region is suppressed.

During offline stimulation, specific brain regions were either activated or suppressed in participants before they engaged in the experimental task. The effect of the stimulation lasted for approximately an hour and encompassed the entire duration of the experiment. In contrast, online stimulation enables the modification of activity in various brain regions while participants are actively engaged in completing the task.

The authors of the study conducted an experiment in which participants experienced cognitive dissonance. Initially, the participants were instructed to evaluate a series of abstract pictures on a scale ranging from 1 to 8, and subsequently, to select one from a pair of similar pictures. During the first evaluation task, participants in some of the pairs evaluated the pictures differently, while in other pairs the ratings were identical.

Immediately after making their selection, participants were asked to re-evaluate the same set of pictures. During this phase, their dorsolateral and medial prefrontal cortex regions—those associated with internal conflict—were subjected to stimulation. The unique experimental block design allowed for the analysis of the preference shifting during the stimulation of specific brain regions at precise time intervals. In essence, it aimed to determine the average increase in scores for selected images and the decrease in scores for unselected alternatives.

In our study, we introduce the use of a high-frequency online block protocol for studying cognitive dissonance dynamics for the first time. Its distinct feature lies in its ability to suppress the brain regions associated with cognitive dissonance, while gradually adjusting the timing of stimulation intervals. Once we gain a precise understanding of the point at which we successfully suppressed preference shifting, we will pinpoint the exact timing of the onset of conflict induced by the choice between the original options and the moment of re-evaluation.

Alina Davydova
Author of the study, Research Assistant, HSE Institute for Cognitive Neuroscience

According to the authors of the study, comprehending the dynamics of cognitive dissonance will contribute to a deeper understanding of the underlying nature of various physical and psychological addictions, which similarly hinge on internal conflict and the challenge of choice.
IQ

October 09, 2023