Summary: Researchers have discovered that a specific region of the brain, the mediodorsal thalamus, can cause feelings of paranoia. By aligning data from studies in monkeys and humans, they found that lesions in this region of the brain led to erratic behavior and an 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.
Highlights:
- The study focused on the orbitofrontal cortex and mediodorsal thalamus.
- Lesions in these areas caused different erratic behaviors in the monkeys.
- The strong paranoia in humans mirrored the volatile perceptions of the apes.
Source: Yale
The ability to adjust one’s beliefs about one’s actions and their consequences in a constantly changing environment is a defining characteristic of advanced cognition. Disruptions in this ability, however, can negatively affect cognition and behavior, leading to states of mind such as paranoia or the belief that others intend to harm us.
In a new study, Yale scientists uncover how a specific region of the brain might cause these feelings of paranoia.
Their new approach – which involved aligning data collected from monkeys with human data – also offers a new cross-species framework through which scientists could better understand human cognition through the study of other species.
Their findings and the approach they used are described June 13 in the journal Cell Reports.
Although previous studies have implicated certain brain regions in paranoia, understanding of the neural underpinnings of paranoia remains limited.
For the new study, the Yale researchers analyzed existing data from previous studies, conducted by several laboratories, on humans and monkeys.
In all previous studies, humans and monkeys performed the same task, showing how volatile or unstable a participant feels their environment is. Participants in each study were presented with three options on a screen, associated with different probabilities of receiving a reward.
If participants selected the option with the highest reward probability, they would obtain a reward with fewer clicks across trials. The option with the lowest probability required more clicks to receive a reward.
The third option, on the other hand, falls somewhere in between. Participants were not provided with information about reward probability and had to discover their best option through trial and error.
After a set number of trials and without warning, the highest and lowest reward probability options reverse.
“Participants therefore have to determine what the best target is, and when a change is perceived in the environment, the participant must then find the new best target,” said Steve Chang, associate professor of psychology and neuroscience at the Faculty of Yale Arts. and sciences and co-senior author of the study.
Participants’ clicking behavior before and after the flip could reveal information about the volatility they perceive of their environment and how their behavior adapts to this 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 the Yale School of Medicine. Medicine and co-senior author of the study. study.
“The computer model is essentially a series of equations that we can use to try to explain behavior. Here it serves as a common language between the human and monkey data and allows us to compare the two and see how the monkey data relates to 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 associated with reward-related decision making, or the mediodorsal thalamus, which sends environmental information to the brain. decision-making control centers of the brain.
Among the human participants, some reported strong paranoia and others did not.
The researchers found that the presence of lesions in both brain regions negatively affected the monkeys’ behavior, but in different ways.
Monkeys with lesions in the orbitofrontal cortex found themselves faced with the same options more often, even after not receiving a reward. In contrast, those with damage to the mediodorsal thalamus showed irregular switching behavior, even after receiving a reward.
They seemed to perceive their environment as particularly volatile, which was similar to what the researchers observed in human participants with high paranoia.
The findings offer new insights into what happens in the human brain — and what role the mediodorsal thalamus might play — when people experience paranoia, the researchers say. And they open the way to the study of complex human behaviors in simpler animals.
“It allows us to ask how we translate what we learn in simpler species — like rats, mice, maybe even invertebrates — to understanding human cognition,” said Corlett, who, with Chang, is member of the Wu Tsai Institute at Yale. which aims to accelerate the understanding of human cognition.
This approach will also allow researchers to evaluate how pharmaceutical treatments that affect conditions like paranoia actually work in the brain.
“And maybe in the future we can use it to find new ways to reduce paranoia in humans,” Chang said.
The work was led by co-first authors Praveen Suthaharan, a graduate student in Corlett’s lab, and Summer Thompson, a research associate in the Yale Department of Psychiatry. This was done in collaboration with Jane Taylor, the Charles BG Murphy Professor of Psychiatry at the Yale School of Medicine.
About this research news in neuroscience and paranoia
Author: Fred Mamoun
Source: Yale
Contact: Fred Mamoun – Yale
Picture: Image is credited to Neuroscience News
Original research: Free access.
“Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, reinforce volatile beliefs linked to paranoia” by Steve Chang et al. Cell Reports
Abstract
Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, reinforce volatile beliefs linked to paranoia
Beliefs – attitudes toward a certain state of the environment – guide the selection of actions and should be robust to variability but sensitive to significant changes.
Beliefs about volatility (expectation of change) are associated with paranoia in humans, but the brain regions responsible for beliefs about volatility remain unknown.
The orbitofrontal cortex (OFC) is central to adaptive behavior, while the magnocellular mediodorsal thalamus (MDmc) is essential for mediating between perceptions and action policies.
We assessed belief updating in a three-choice probabilistic reversal learning task following excitotoxic lesions of the MDmc (not = 3) or OFC (not = 3) and compared the performances with those of non-operated monkeys (not = 14).
Computational analyzes indicated a double dissociation: MDmc lesions, but not OFC, were associated with erratic switching behavior and increased volatility beliefs (as in paranoia in humans), while OFC lesions , but not MDmc, were associated with increased stay-loss behavior and reward. learning rate.
Given the consistency across species and models, these results have implications for understanding paranoia.