Impossible to react in the face of uncertainty. This may be a sign of the early stages of psychosis, according to a French study.
The early stages of psychosis interfere with decision making. This is shown by a study carried out at Sainte-Anne hospital (Paris) and published in Molecular Psychiatry. Researchers have studied how healthy people react to uncertainty. The stage preceding the psychotic episode results in a kind of blockage.
As part of the study, 31 healthy participants were recruited. Aged 25 to 37, they were right-handed, with left-handed people at greater risk for psychosis. All of them participated in a computer betting game. In one case, they had an 80% chance of winning a pound (1.4 euros), in the other case, an 80% chance of winning 10 pence (0.14 euros).
Mimic psychosis
To confuse participants, the team upset the rules after each block of 60 situations. A symbol that made money started to lose money, and vice versa. The objective was to find out whether or not the early stages of psychosis alter behavior in the face of uncertainty.
In order to mimic the onset of a psychotic episode, the researchers administered a low dose of ketamine intravenously to some patients, and to others a placebo. The anesthetic, given in very small doses, causes symptoms similar to those seen at the onset of a psychotic attack. Brain activity was continuously measured by functional MRI to determine the effects of the drug.
Fewer winning symbols
Ketamine does not affect the impulsiveness of participants’ choices or actions. On the other hand, it disrupts the optimization of choices. In participants under anesthetic, only the first series of choices is really optimal. The effect is even more marked on the last block.
According to the authors, the drug impairs the ability to distinguish stable periods in the rules of the game, and therefore to predict its behavior. Participants therefore do not bet on the winning symbols.
“This study characterizes the key role of adaptation to uncertainty in decision-making and its disruption in the early stages of psychosis,” summarizes Raphaël Gaillard, professor of psychiatry at the University of Paris-Descartes. It should make it possible to better understand the emergence of delirium and to guide therapeutic innovation. “
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