summary: Researchers have discovered that a specific region of the brain, the mediodorsal thalamus, may trigger feelings of paranoia. By harmonizing data from studies in monkeys and humans, they found that lesions in this area of the brain led to erratic behavior and increased perceptions of environmental variability.
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 issues.
Key facts:
- The study focused on the orbitofrontal cortex and the mediodorsal thalamus.
- Lesions in these areas caused various erratic behaviors in the monkeys.
- The rise in paranoia in humans mirrors the volatile perceptions of apes.
source: Yale
The ability to modify beliefs about one’s actions and their consequences in a constantly changing environment is a hallmark of advanced cognition. However, disrupting this ability can negatively affect cognition and behavior, leading to mental states such as paranoia, or the belief that others intend to harm us.
In a new study, Yale scientists have discovered how a specific region of the brain can trigger these feelings of paranoia.
Their new approach – which involves aligning data collected from monkeys with human data – also offers a new cross-species framework through which scientists can better understand human cognition by studying other species.
Their findings and the method they used were described June 13 in the journal Cell reports.
While previous studies have implicated certain brain regions in paranoia, understanding of the neural underpinnings of paranoia remains limited.
For the new study, researchers at Yale University analyzed existing data from previous studies, conducted by multiple laboratories, in both humans and monkeys.
In all previous studies, humans and monkeys performed the same task, which demonstrates how volatile or unstable the participant believes their environment is. Participants in each study were given three options on the screen, which were associated with different probabilities of receiving a reward.
If participants selected the option with the highest probability of reward, they would receive a reward with fewer clicks across trials. The lower probability option requires a higher number of clicks to get the reward.
Meanwhile, the third option was somewhere in the middle. Participants had no information about the reward probability and had to uncover their best choice by trial and error.
After a set number of attempts and without warning, the highest and lowest reward probability options flip.
“So participants have to figure out what the best target is, and when there is a noticeable change in the environment, the participant then has to find a new best target,” said Steve Chang, an assistant professor of psychology and neuroscience at Yale University’s School of Liberal Arts. Sciences and co-lead author of the study.
Participants’ pre- and post-face clicking behavior can reveal information about how much variability they perceive in their environment and how well their behavior adapts to 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 University School of Medicine and co-lead author of the study. Stady.
“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 the two and see how the monkey data relates to the 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 in the brain.
Among the human participants, some reported higher paranoia and others 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 often stick with the same choices even after no longer receiving a reward. On the other hand, those with lesions in the mediodorsal thalamus showed erratic switching behavior, even after receiving a reward.
They seemed to perceive their environments as particularly volatile, which was similar to what the researchers observed in human participants with severe paranoia.
Researchers say the findings provide new information about what happens in the human brain — and what role the mediodorsal thalamus may play — when people experience paranoia. They provide a path to how to study complex human behaviors in simpler animals.
“It allows us to ask how what we learn in simpler species — such as rats, mice and perhaps even invertebrates — translates to understanding human cognition,” said Corlett, who he and Zhang are members of the Wu Tsai Institute at Yale University. Which aims to accelerate the understanding of human cognition.
This approach will also allow researchers to evaluate how pharmaceutical treatments that affect conditions such as paranoia work in the brain.
“Maybe we can use it in the future to find new ways to reduce paranoia in humans,” Zhang said.
This work was led by co-authors Praveen Suthaharan, a graduate student in Corlett’s lab, and Summer Thompson, an associate research scientist in the Department of Psychiatry at Yale University. This was done in collaboration with Jane Taylor, the Charles P. J. Murphy Professor of Psychiatry at Yale University School of Medicine.
About neuroscience and paranoia research news
author: Farid Mamoun
source: Yale
communication: Farid Mamoun – Yale
picture: Image credited to Neuroscience News
Original search: Open access.
“Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, enhance paranoia-related volatility beliefs.“By Steve Chang et al. Cell reports
a summary
Lesions of the mediodorsal thalamus, but not the orbitofrontal cortex, enhance paranoia-related volatility beliefs.
Beliefs—attitudes toward some state of the environment—guide action choice and must be robust to fluctuations but sensitive to meaningful change.
Beliefs about volatility (expectation of change) are associated with paranoia in humans, but the brain areas responsible for volatility beliefs remain unknown.
The orbitofrontal cortex (OFC) is a key component of adaptive behavior, while the mesolimbic dorsal thalamus (MDmc) is essential for arbitrating perceptions and action policies.
We assessed belief updating in a three-choice probabilistic reversal learning task after excitotoxic lesions in the MDmc (n = 3) or OFC (n = 3) and compare the performance with the performance of non-working monkeys (n = 14).
Computational analyzes indicated a double dissociation: lesions of the MDmc, but not the OFC, were associated with erratic switching behavior and increased belief in volatility (as in paranoia in humans), whereas lesions of the OFC, but not the MDmc, were associated with increased loss-reward behavior. Learning rates.
Given the concordance across types and models, these findings have implications for understanding paranoia.
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