Which factors determine what we believe about our world, ourselves, our past, and our future? Cognitive neuroscience suggests that our beliefs are dependent on brain activity, specifically on the way our brains process sensory information in order to make sense of our environment.
These beliefs (defined as probability estimates) are central to our brain’s predictive processing function, which enables it to predict the probabilistic structure of the world around us. These predictions could even be the fundamental building blocks of mental states, such as perceptions and emotions.
Many psychiatric disorders, such as depression and schizophrenia, are characterised by irregular beliefs whose origins we still don’t fully understand. But if we can identify the cerebral systems governing them, we could target those very areas in a bid to alleviate the pain associated to these illnesses.
Decoding belief mechanisms in psychiatry
This is one of the findings of our study recently published in the journal JAMA Psychiatry. For this study, I explored with my team how the dissociative psychotropic, ketamine, affects mechanisms of belief updating (i.e., how we change our beliefs upon receiving information) in patients with treatment-resistant depression.
While traditional antidepressants take weeks to show any results, ketamine – an antagonist molecule that acts on the NMDA (N-methyl-D-aspartate) receptors – produces antidepressant effects within hours. When administered, it also causes a dissociative experience of depersonalisation typically associated with a sensation of leaving the body (known as “autoscopy”).
Given that ketamine’s rapid action and unexpected dissociative effects make it a potentially worthwhile option for treating mental health problems, we are on a mission to unpack this mystery, at the crossroads between pharmacology and neuroscience.
Cognitive-affective biases in depression
According to the World Health Organization, depression affects approximately 280 million people in the world and 700 000 people die due to suicide every year. One of the most specific symptoms of depression is depressive beliefs (e.g., pessimism, self-deprecation, rejection, and feelings of failure), described as “mood-congruent” beliefs when their content matches the subject’s affective state.
By influencing the patient’s perception and action, these beliefs play a vital role in triggering the phenomenon of negative auto-reinforcement. For example, the belief that we have been rejected by our peers gradually makes us more withdrawn, which in turn reinforces feelings of worthlessness. Once this feedback loop has been closed, it can be difficult not to spiral downward.
Individuals with depression find themselves trapped in a vicious circle, placing negative bias on their perception and actions, which contribute to long-term symptoms of mental illness.
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La suite est à lire sur: theconversation.com
Auteur: Hugo Bottemanne, Psychiatre à la Pitié-Salpêtrière & chercheur à l’Institut du Cerveau – Sorbonne Université AP-HP, Sorbonne Université
