A team of researchers led by the Universitat Autònoma de Barcelona (UAB) has made a significant breakthrough in comprehending the mechanisms of predictive processing in the human brain. They have discovered that non-invasive electrical stimulation can modulate this process. The study, directed by Lorena Chanes, an associate and ICREA Acadèmia professor, involved collaboration between the UAB’s Institute for Neuroscience (INc-UAB), the Department of Clinical and Health Psychology, the Mayo Clinic, and the University of Munich. The findings were recently published in the journal Cerebral Cortex.
Predictive processing is a crucial aspect of how the human brain operates. It constantly predicts incoming sensory information based on an internal model constructed from past experiences. These predictions are compared to the actual sensory input, and any disparities are used to update the internal model, minimizing future errors.
According to existing literature, predictive processing is implemented in the brain through signals that propagate as waves across different frequency bands in the brain cortex. Beta oscillations (13–30 Hz) are responsible for conveying predictions, while gamma oscillations (30–90 Hz) transmit prediction errors. In their study, the researchers utilized non-invasive electrical stimulation on a specific region of the left prefrontal cortex to selectively modulate these signals. They aimed to investigate the impact of this modulation on emotional prediction and social perception tasks.
The study involved 75 participants who were tasked with predicting the facial expressions of individuals reacting to different emotional contexts involving happiness, sadness, or fear. Throughout the task, the researchers applied non-invasive electrical stimulation to the participants using an electrode helmet, simultaneously recording brain activity with electroencephalography.
The results revealed that stimulation at a frequency of 20 Hz (within the beta oscillations range) influenced facial expression predictions, making them more stereotypical. When participants were stimulated, they were more inclined to expect a smiling expression in a happiness-evoking situation, a pouting expression in a sadness-evoking situation, and wide-open eyes in a fear-evoking situation. Electroencephalography data also demonstrated an increase in brain activity at the frequency band used in the stimulated area.
Lorena Chanes emphasized, “This result, together with the absence of modulation at a different frequency, demonstrates that predictive processing is encoded in the brain using specific frequency bands and can be non-invasively modulated to ‘artificially’ modify behavior in a task.”
This study provides valuable insights into the neural mechanisms of predictive processing, which may facilitate understanding of how disruptions in this process occur in brain-related conditions and how they can potentially be restored using non-invasive methods. Chanes noted that an increasing number of conditions are being attributed to disruptions in predictive processing, such as in a previous study related to depression. While the observed effects are modest, they may open avenues for developing therapies based on these types of modulations.
The authors of the study also suggest that their findings may extend beyond social perception and have implications for other cognitive tasks. Predictive processing is a fundamental mechanism of brain function, and similar modulations could potentially be observed in other domains. Exploring this possibility will be a focus of future research.