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. Credit: Neuroscience News
Summary: 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 demonstrated that the human brain processes predictions using signals that traverse the brain cortex on specific frequency bands.
The researchers used non-invasive electrical stimulation on the left prefrontal cortex of participants, which influenced their predictions of emotional facial expressions, making them more stereotypical.
The findings of the study indicate that predictive processing disruptions, such as those seen in depression, could potentially be restored using non-invasive methods, paving the way for future therapies.
A research team led by the Universitat Autònoma de Barcelona (UAB) has made a key advance in understanding how predictive processing is enabled and implemented in the human brain, showing that it may be modulated through non-invasive electrical stimulation.
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.
About this neuroscience research news
Author: Maria Jesus Delgado Source: UAB Contact: Maria Jesus Delgado – UAB Image: The image is credited to Neuroscience News
Noninvasive modulation of predictive coding in humans: causal evidence for frequency-specific temporal dynamics
Increasing evidence indicates that the brain predicts sensory input based on past experiences, importantly constraining how we experience the world. Despite a growing interest on this framework, known as predictive coding, most of such approaches to multiple psychological domains continue to be theoretical or primarily provide correlational evidence.
We here explored the neural basis of predictive processing using noninvasive brain stimulation and provide causal evidence of frequency-specific modulations in humans.
Participants received 20 Hz (associated with top-down/predictions), 50 Hz (associated with bottom-up/prediction errors), or sham transcranial alternating current stimulation on the left dorsolateral prefrontal cortex while performing a social perception task in which facial expression predictions were induced and subsequently confirmed or violated. Left prefrontal 20 Hz stimulation reinforced stereotypical predictions. In contrast, 50 Hz and sham stimulation failed to yield any significant behavioral effects.
Moreover, the frequency-specific effect observed was further supported by electroencephalography data, which showed a boost of brain activity at the stimulated frequency band.
These observations provide causal evidence for how predictive processing may be enabled in the human brain, setting up a needed framework to understand how it may be disrupted across brain-related conditions and potentially restored through noninvasive methods.