The multicentre study was coordinated by Miquel Àngel Fullana, an investigator from the IDIBAPS research group in Imaging of Mood- and Anxiety-Related Disorders (IMARD), but researchers from other Catalan institutions such as the Bellvitge Biomedical Research Institute (IDIBELL) and the Institut de Recerca Sant Pau (IR Sant Pau) have also participated, as well as international institutions from the United States, Australia, and Germany.
“Fear conditioning is a basic learning process: if a person associates a sound with an unpleasant stimulus, such as a small electric shock, they end up responding with fear when they hear the sound,” explains Joaquim Raduà, first author of the study and head of the IDIBAPS research group. This ability has been critical for survival, but when it becomes dysregulated it could lie behind many mental disorders. To study this, the team analysed functional magnetic resonance imaging images of more than 2,000 people, making it the largest study carried out to date in this field.
The results show that this type of learning activates regions of the brain involved in the detection of danger signals and in the body's response to emotions, such as salience and autonomic activation networks. In addition, it was seen that there are notable differences depending on how the experiments have been designed: for example, depending on the instructions given to the participant, or depending on what type of unpleasant stimulus is used. The study has also shown that there are substantial differences in the magnitude of brain activations between people. “With such large, consistent, harmonised data processing, we have been able to see which results are consistent and which depend on the specific conditions of each study,” explains Miquel Àngel Fullana.
Another key aspect has been the comparison between healthy people and people with mental disorders. According to Enric Vilajosana, another also an IDIBAPS researcher, the study reveals that the brains of people with anxiety or depressive disorders respond differently, and that in conditions such as post-traumatic stress disorder and OCD, the deviations are especially marked.
According to the authors, this research marks a before and after in the study of fear conditioning. On the one hand, it shows that, if one works with large groups of participants and well-harmonised data, one can identify the brain circuits involved very precisely. On the other, the differences found between people with and without mental disorders and between individuals open up new opportunities for developing both tests that aid diagnosis and treatments adapted to each patient.
