Brain Stimulation Modulates Emotional Prediction

  A new study provides a fresh understanding of how the brain processes predictions, a crucial component of how we perceive and interact with the world. Researchers used non-invasive electrical stimulation on participants’ brains to observe its effects on predicting emotional facial expressions. 

The results highlighted the potential to modulate predictive processing and its implications for conditions like depression, opening doors to future research and therapeutic interventions.

The study was conducted by a team from the Institute for Neuroscience (Inc-UAB), the Department of Clinical and Health Psychology, the Mayo Clinic, and the University of Munich. It was directed by Lorena Chanes, associate and ICREA Acadèmia professor. 

The findings are published in Cerebral Cortex. 

The human brain works predictively, constantly anticipating sensory input based on an internal model of the world based on past experiences. Predictions are compared to actual sensory input, and the difference is used to update the model if needed, in order to minimize future errors.

According to existing literature, predictive processing is implemented in the brain with signals that “travel” as waves through several parts of the brain cortex on different frequency bands: beta oscillations (13-30 Hz) for predictions and gamma oscillations (30-90 Hz) for prediction errors.

In this study, researchers used non-invasive electrical stimulations on a left prefrontal cortex area to modulate these signals selectively and test their effect on an emotional prediction and social perception task.

The study involved 75 participants, who were asked to predict the facial expressions of a variety of individuals reacting to different emotional contexts evoking happiness, sadness, or fear.

During the task, researchers applied non-invasive electrical stimulation to the participants using an electrodes helmet, and at the same time recorded brain activity with electroencephalography. 

Researchers observed that stimulation at a frequency of 20 Hz (within the beta oscillations range) had an effect on facial expression predictions, making them more stereotypical. When stimulated, participants tended to expect, to a greater extent than when not, a smiling expression in a situation that evoked happiness, a pouting expression in a situation evoking sadness, and a face with its eyes wide open in a situation evoking fear.

The impact of electrical stimulation was also observed on electroencephalography, which showed an increase in brain activity on the frequency band of the frequency used in the area where it was applied. 

“This result, together with the absence of a modulation at a different frequency, demonstrates that predictive processing is coded in the brain on specific frequency bands and that it may be modulated non-invasive ‘at will’ in order to ‘artificially’ modify behavior in a task,” Lorena Chanes points out. 

The study provides new information on the neural basis of predictive processing, setting up the stage to understand how it can be disrupted in brain-related conditions and, potentially, restored using non-invasive methods.

“An increasing number of conditions are being described in terms of predictive processing disruptions, as seen for example in a previous study related to depression. In this sense, although the effect observed is small, it may open the door to developing therapies based on these types of modulations”, the UAB researcher adds. 

The authors also point out that their observations could extend beyond the area of social perception. 

“Predictive processing is a fundamental mechanism of brain function and, thus, its implications go beyond the field of study of facial expressions and social perception. It is possible that similar modulations to the ones observed in this

study may be observed on other cognitive tasks. This will be something to explore in future research”, researchers state.

Reference