It has been known for decades that the classic symptoms of schizophrenia, such as jumping to conclusions or difficulty adapting to new information, can be attributed to poor communication between the cerebral cortex and the thalamus, known as the brain’s central switch. .
Now, in a study published in the journal ‘Cell Reports Medicine’, which has measured the activity of brain cells between these two regions in a group of volunteers while they completed complex tasks, a team of researchers from the School of Medicine of Tufts University and Vanderbilt University School of Medicine (USA) have found a way to use a person’s sensitivity to uncertainty as a diagnostic tool.
According to research results, people with schizophrenia generate different neural patterns when asked to make decisions based on conflicting information.
The work offers one of the first biological tests to assess whether someone is prone to inflexible thinking and, by monitoring changes in these patterns, a new way to measure whether treatments are working.
“Our goal was to obtain a biomarker of executive dysfunction in schizophrenia, which only arises when patients are forced to perform an ambiguous task,” says physician-scientist Michael Halassa of Tufts University, who led the study along with Neil Woodward, neuropsychologist at Vanderbilt University. “As humans, we make decisions that are hierarchical in nature all the time, which means we often have to take into account misinformation at different levels, but this breaks down in schizophrenia and here is a way we can start to measure that attribute.
Throughout the evolution, The human brain has developed ways to “vote” on which pieces of information are most relevant when making decisions. decisions.
For example, if you go to your favorite restaurant but the food is not of the quality you expected, you may think that the chef is not there or that he has had a bad night, but that does not stop you from returning.
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In contrast, a person with schizophrenia may be unable to consider the evidence that the last 20 or 30 visits were excellent and will no longer want to return to the restaurant.
Animal studies have shown that this behavior is due to deficiencies in the interaction between the part of the forebrain that helps animals interpret complex signals (the dorsolateral prefrontal cortex) and a subcortical region associated with conflict resolution and communication. decision making (the mediodorsal thalamus).
Based on data obtained in animals, the research team developed a series of cognitive and imaging tests to better understand this neural circuit in humans and establish more accurate diagnoses for patients.
In the study, 40 study participants (a mix of neurotypical people and patients with schizophrenia) were asked to correctly choose the location of a target based on a sequence of cues that can become more or less conflicting.
In the case of healthy people, performance was very good even when conflict was high.
But in people with schizophrenia, they had comparable behavior to controls when there was little conflict, but they made many more errors with levels of conflict that were well tolerated by controls.
Patients with schizophrenia do not respond as well when things become more ambiguous
“If you look at behavior, there is a greater susceptibility to sensory noise, so patients with schizophrenia do not respond as well when things become more ambiguous,” explains Anna Huang, co-lead author of the study. “These results were correlated with thalamus and frontal cortex deficits “that we were able to capture in brain activity readings, predicting a person’s ability to process conflicting information in perceptual and memory tasks.”
The researchers plan to validate their findings by replicating the methods with a broader range of people who will undergo brain scans while processing ambiguous signals.
They also plan to manage hierarchical tasks to these people, similar to the restaurant example mentioned above.
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