Summary: Scientists have discovered that a certain area of ​​the brain, the mediodorsal thalamus, can trigger feelings of paranoia. By comparing data from monkey and human studies, they found that lesions in this brain region led to erratic behavior and increased perception of environmental volatility.
The study offers a new framework for understanding human cognition through cross-species research. These findings could pave the way for the development of targeted treatments for paranoia and other cognitive problems.
Key facts:
- The study focused on the orbitofrontal cortex and the mediodorsal thalamus.
- Lesions in these areas produced a variety of erratic behaviors in the monkeys.
- High paranoia in humans mirrored the volatile perception of monkeys.
Source: Yale
The ability to adjust beliefs about one’s actions and their consequences in a constantly changing environment is a defining characteristic of advanced cognition. However, impairment of this ability can negatively affect cognition and behavior, leading to such states of mind as paranoia or the belief that others are out to harm us.
In a new study, Yale researchers reveal how one particular area of ​​the brain can causally trigger these feelings of paranoia.
Their new approach—which involved matching data collected from monkeys with human data—also offers a new cross-species framework through which scientists could better understand human cognition by studying other species.
Their findings and the approach they used are described in the June 13 issue of the journal Cell messages.
While past studies have implicated some brain regions in paranoia, understanding of the neural underpinnings of paranoia remains limited.
For the new study, Yale researchers analyzed existing data from previous studies conducted by several laboratories in both humans and monkeys.
In all previous studies, humans and monkeys performed the same task, which captures how volatile or unstable the participant thinks their environment is. Participants in each study were presented with three options on the screen that were associated with different probabilities of receiving a reward.
If participants chose the option with the highest reward probability, they would receive the reward with fewer clicks across trials. The option with the lowest probability required more clicks to earn a reward.
The third option, meanwhile, was somewhere in the middle. Participants had no information about the probability of reward and had to discover their best option by trial and error.
After a set number of trials and without warning, the highest and lowest reward probability options are reversed.
“So participants have to figure out what the best goal is, and when there’s a perceived change in the environment, the participant then has to find a new best goal,” said Steve Chang, associate professor of psychology and neuroscience at the Yale School of Arts. and Sciences and co-author of the study.
Participants’ clicking behavior before and after flipping can reveal information about how volatile they perceive their environment to be and how adaptive their behavior is in that changing environment.
“Not only did we use data in which monkeys and humans performed the same task, but we also applied the same computational analysis to both data sets,” said Philip Corlett, associate professor of psychiatry at Yale School of Medicine and co-author of the study. studies.
“A computational model is basically a series of equations that we can use to try to explain behavior, and here it serves as a common language between the human and monkey data and allows us to compare them and see how the monkey data relates to the data. human data.”
In previous studies, some monkeys had small but specific lesions in one of two brain regions of interest: the orbitofrontal cortex, which has been linked to reward-related decision-making, or the mediodorsal thalamus, which sends information about the environment to the brain’s decision-making control center.
Among the human participants, some reported high paranoia and some did not.
The researchers found that the presence of lesions in both areas of the brain negatively affected the behavior of the monkeys, but in different ways.
Monkeys with lesions in the orbitofrontal cortex were more likely to stick with the same choices even after not receiving a reward. Those with lesions in the mediodorsal thalamus, on the other hand, showed erratic switching behavior, even after receiving a reward.
They seemed to perceive their environment as particularly unstable, which was similar to what the researchers observed in human participants with high paranoia.
The findings offer new information about what happens in the human brain — and the role the mediodorsal thalamus may play — when people experience paranoia, the researchers say. And they provide a way to study complex human behavior in simpler animals.
“It allows us to ask how we can translate what we learn in simpler species — like rats, mice, maybe even invertebrates — to understanding human cognition,” said Corlett, who is a member of Yale’s Wu Tsai Institute with Chang . which aims to accelerate the understanding of human cognition.
The approach will also allow researchers to assess how pharmaceutical treatments that affect conditions such as paranoia actually work in the brain.
“And maybe over time we can use that to find new ways to reduce paranoia in people,” Chang said.
The work was led by co-authors Praveen Suthaharan, a graduate student in Corlett’s lab, and Summer Thompson, an associate research fellow in the Yale Department of Psychiatry. It was done in collaboration with Jane Taylor, the Charles BG Murphy Professor of Psychiatry at the Yale School of Medicine.
About this neuroscience and paranoia research news
Author: Fred Mamoun
Source: Yale
Contact: Fred Mamoun—Yale
Picture: Image is credited to Neuroscience News
Original Research: Open access.
“Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, enhance paranoia-associated volatility beliefs” Steve Chang et al. Cell messages
Abstract
Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, increase paranoia-related volatility beliefs
Beliefs—attitudes about a particular state of the environment—guide the choice of action and should be resistant to variability but sensitive to meaningful change.
Volatility beliefs (expectations of change) are associated with paranoia in humans, but the brain regions responsible for volatility beliefs remain unknown.
The orbitofrontal cortex (OFC) is central to adaptive behavior, while the magnocellular mediodorsal thalamus (MDmc) is essential for deciding between perception and action policy.
We assessed belief updating in a three-choice probabilistic reversal learning task following excitotoxic lesions of the MDmc (n = 3) or OFC (n = 3) and compared performance with that of unoperated monkeys (n = 14).
Computational analyzes showed a double dissociation: lesions of MDmc, but not OFC, were associated with erratic switching behavior and increased beliefs about volatility (as in paranoia in humans), whereas lesions of OFC, but not MDmc, were associated with increased loss behavior and reward learning rate .
Given the concordance across species and models, these results have implications for understanding paranoia.