Often dismissed as an irrational or exaggerated sense of worry, paranoia extends from a very rational ability to keep our wits about us in a chaotic environment.
If we can adapt quickly, we can stay alive when circumstances do change. At the extreme, however, delusions in the evil intentions of others can be socially isolating, robbing people of the ability to maintain healthy relationships and hold down jobs.
To better understand why some brains figuratively jump on shadows more than others, a team of researchers led by Yale University psychiatrists Praveen Suthaharan and Summer Thompson analyzed the results of a simple test on a group of male rhesus monkeys and human volunteers.
The test, called a probabilistic reversal learning (PRL) task, revolved around the selection of a symbol for a chance at a reward: food for monkeys and points for humans.
Different symbols offered different chances of success, so given a choice of three on a screen, the subject was given the opportunity to learn which symbol was most likely to yield a reward.
Just when the subjects thought they had it all figured out after half the test runs, the trial results were reversed, with the happiest symbol paying out rewards less often and the unluckiest symbol now becoming the optimal choice.
“So participants have to figure out what the best target is, and when a change in the environment is observed, the participant has to find the new best target,” says Yale psychologist Steve Chang.
Six of the 20 macaques had previously undergone a neurological procedure in separate studies that affected either their dorsal thalamic nuclei – an area thought to play a role in planning, abstract thinking and organization – or an area in their prefrontal cortex that is involved in decision-making. .
Human volunteers, on the other hand, had to complete a thinking scale questionnaire to assess their level of paranoia, and a second survey to determine signs of possible depression.
By analyzing the behavior of the monkeys and humans before and after the switch and comparing the results with those of the studies, the team was able to assess which of the compromised brain areas could affect the monkey’s ability to cool through the volatile navigate the game environment. .
“Not only did we use data in which monkeys and humans performed the same task, we also applied the same computational analysis to both data sets,” says Yale psychiatrist Philip Corlett.
The data indicated that both the magnocellular mediodorsal thalamus (MDmc) in the dorsal thalamic nucleus and locations in the orbitofrontal cortex (known as Walker’s areas 11, 13, and 14) all influenced the monkey’s behavior in subtly different ways after the switch from the test.
For those in congested Walker areas, the sudden loss of reward had little impact on their decisions to switch. The monkeys continued to tap what they thought was the ‘winning’ ticket with reckless abandon.
Those whose MDmc was corrupted exhibited the exact opposite behavior, switching back and forth even after discovering that the new “big chance” symbol was paying out rewards, almost as if they suspected the system was rigged against them personally.
This was similar to behavior observed in people with survey responses indicating higher levels of paranoia.
While delusions and acts of paranoia are undoubtedly complex behaviors involving different mindsets and different parts of the brain, drawing a line between a particular area and volatile decision-making could inform future studies that could lead to new therapies or help us can help you better understand how certain actions can be performed. increases the risk of psychosis.
“Maybe in the future we can use it to find new ways to reduce paranoia in people,” says Chang.
This research was published in Cell reports.