When learning, patients with schizophrenia or depression they have difficulty making optimal use of information that is new to them. In the learning process, both groups of patients give more weight to less important information and, as a result, make less than ideal decisions.
In that regard, it is state published a study in Brain.
Depression and difficulties in the apartment: that's why
This is the conclusion of a study lasting several months conducted by a team led by neuroscientist Professor Dr. med. Markus Ullsperger from the Institute of Psychology at the Otto von Guericke University of Magdeburg in collaboration with colleagues from the University Clinic for Psychiatry and Psychotherapy and the German Center for Mental Health.
Using electroencephalography (EEG) and complex computer mathematical models, the team of researchers found that learning deficits in patients with depression and schizophrenia are caused by reduced flexibility in using new information.
“People with depression or schizophrenia often suffer from cognitive limitations,” says the study's lead author, Dr. Hans Kirschner. For example, they find it difficult to understand complex information, learn, plan, or generalize a situation. “In particular, the deficit in using past feedback to manage future behavior poses a fundamental problem for those affected.”
Dr. Tilmann Klein, neuropsychologist and psychotherapist, adds that these cognitive limitations are very burdensome for the affected patient groups and have a strong influence on the outcome of treatment. “If we better understand these deficits and their causes, in the long term we will be able to design more specific and targeted forms of treatment, such as functional training.”
To find out whether the psychological and neural mechanisms that lead to cognitive limitations are the same in different mental disorders, scientists examined patients diagnosed with severe depression and schizophrenia, as well as a control group of 33 people.
Test subjects were repeatedly presented with images of animals on a screen that were associated with a high or low probability of reward or punishment, i.e. positive or negative feedback. The test participants had to decide whether or not to bet on the animal and therefore win or lose 10 points. If they had not bet, they would have neither won nor lost anything, but they would then have seen what would have happened if they had decided to bet.
Dr. Kirschner describes the structure of the test as follows: “During the experiment, the participants' goal is to find out whether it was worth betting and therefore risking the loss it might entail, or whether it was better not to bet and thus avoid LOSE .”
“The process is a bit like playing roulette,” explains the neuroscientist. “If you bet, you either win or lose. If you don't bet, you can still see where the ball lands and you can understand what would have happened if you had bet.
The difference in our study is that the participants were actually able to learn because over time they came to realize whether an animal was, on average, more likely to be rewarded or punished and could therefore always bet on the animal and therefore maximize their winnings or minimizing their losses.”
According to Kirschner, optimal learning in this task would mean that test subjects paid more attention to feedback – that is, an animal's victories or defeats – early in the learning process.
“Once they have an idea of an animal's probability of winning, they ignore misleading feedback, for example, an image that usually has a high probability of losing also occasionally wins.”
While healthy control participants did exactly that, patient groups suffering from depression or schizophrenia were more strongly affected by errors that occurred randomly. “Imagine a basketball player throwing balls into a hoop,” Dr. Kirschner continues.
“A poor player rarely scores and isn't picked for the team. Even if he doesn't score every time, a good player scores often and thus gets picked for the team. However, in the study, both groups of patients would replace the good player after a bad shot.”
In the EEG it can be seen that both groups of patients have a reduced neuronal representation of reward expectancy. “This means that a good basketball player's scoring percentage is not stored as well in the brain and is overwritten more quickly when the player occasionally fails to score.”
In summary, Dr. Kirschner explains that the study expanded the team's knowledge of cognitive limitations in patients diagnosed with schizophrenia or depression. “In particular we were also able to demonstrate the advantages of computer models in which we try to mathematically describe complex learning mechanisms and implement them in the form of computer simulations.”
This made it possible to simulate learning behaviors that were difficult to predict and compare them with the behavior of participants in specific tasks. “With this approach in the future, we will be able to quantify and characterize learning deficits in a more nuanced way.
And a better understanding of these deficits, in turn, will help guide us towards further developing existing treatments for depression and schizophrenia. in a more targeted way. We hope that in the future our research will benefit patients with learning disabilities and help them cope better with their daily lives.”
Scientists at the Max Planck Institute for Psychiatry measured the pupil reaction of participants while solving a task. In healthy participants, pupils dilated during the reward waiting task, but this reaction was less pronounced in participants with depression.
“The reduced pupil reaction was particularly evident in patients who could no longer experience pleasure and reported a loss of energy,” says Andy Brendler, first author of the study. This feeling of listlessness is one of the most common symptoms of depression.
“This discovery helps us better understand the physiological mechanisms underlying apathy,” explains research group leader Victor Spoormaker. Among other things, the pupillary reaction is an indicator of activity in the locus coeruleus, the brain structure with the highest concentration of noradrenergic neurons in the central nervous system.
Noradrenergic neurons react to the neurotransmitter norepinephrine, an essential component in the stress response and upregulation of arousal, in other words, the activation of the nervous system. “The reduced pupillary response in patients with increased listlessness indicates that the lack of activation of the locus coeruleus is an important physiological process that underlies the feeling of listlessness,” says Spoormaker.
The study also found that the students' response was weaker the greater the participants' depressive symptoms. This replicates the findings of a previous study by the same research group. The replicability of neuropsychiatric methods represents more the exception than the rule and demonstrates the reliability of pupillometry as a method.
Pupillometry could be used as a supplementary method for diagnosis. It could also contribute to the development of individualized treatment strategies for depression. For example, if a patient shows significantly reduced pupillary response, antidepressants that affect the noradrenergic system may be more effective than other medications. The dosage of the drug could also be optimized based on the pupil's reaction.
Considering that approximately 30% of depressed patients do not improve with currently available medications, it is urgently necessary to understand the physiological mechanisms underlying depression and develop diagnosis and treatment accordingly.
When people win or lose something, their pupils dilate slightly. The researchers found that this dilation is less pronounced in patients with severe depression than in healthy people. The more seriously ill the patients were, the less the pupil opened. In the long term, this discovery could lead to a more substantiated diagnosis, which is not only based on patient statements, but is also measured biologically. This could lead to more individualized treatment.
For decades, scientists have tried to find out whether patients with depression value rewards less than non-depressed individuals. Study participants at the Max Planck Institute for Psychiatry played a simple game while in front of the magnetic resonance imaging (MRI) scanner, where they could win a small sum of money.
Winning money is a clear incentive known to cause pupil dilation in healthy people. The researchers measured the pupils of the study participants extremely accurately and at an extremely high speed: using a special setup, they managed to take 250 images per second; for comparison, we only blink every four to six seconds.
For the first time, Max Planck scientists have managed to demonstrate a correlation between pupil dilation in response to an expected reward and the severity of depression. The more severe the symptoms of depression, the less dilated the pupils would become.
The study shows that the prospect of a reward in severely depressed patients does not lead to the same behavioral activation as in healthy individuals. Even with such a positive expectation, their nervous system may activate less strongly.
“We suspect that behind this there is a physiological system that could explain the anhedonia often reported in patients,” says study leader Victor Spoormaker.
Researchers at the Max Planck Institute believe that psychiatric disorders should be grouped differently than current diagnostic groups. The decisive factor would be biological data, such as pupil dilation, which can be clearly measured.
Patients with depression who react less strongly with their pupils would form a separate subgroup. “Then we could treat these patients in a more targeted way,” concludes Spoormaker.
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