Insights & Outcomes: Cravings, queasiness, and vicarious thrills
This month, Insights & Outcomes is coming at you with all the feels — from the neurological underpinnings of vicarious thrills and the biological network that influences cravings, to the brain’s connections to physical frailty and the queasiness that can come from bacteria bolstered by climate change.
A biomarker for craving
Yale researchers have developed a brain network model that can predict food and drug craving in people with and without addictive disorders. This “craving network,” the researchers say, could serve as a biomarker for substance use risk and treatment response in the future.
The findings were published in the American Journal of Psychiatry.
“Craving is a key aspect of addiction, and it can predict the likelihood of future substance use or how someone might respond to treatment,” said Kathleen Garrison, associate professor of psychiatry at Yale School of Medicine and lead author of the study. “It’s also experienced by people without addictions. But there’s limited research on how brain connectivity predicts the feelings of craving.”
For the new study, researchers used neuroimaging data to evaluate brain functional connectivity while individuals were asked to imagine personal experiences with drugs or their favorite foods; stressful experiences, such as break-ups; and relaxing experiences, like sitting in a park. Participants included adults with alcohol or cocaine use disorders or obesity, adults without substance use disorders, and adolescents with and without prenatal cocaine exposure. Each participant rated their level of craving of food or drugs before and after each imagery task.
The researchers then used machine learning to determine whether any common brain connectivity pattern related to craving levels was observed across participants.
The model successfully predicted self-reported craving levels among all individuals, the researchers said; the brain network they identified in the study was complex, including many different brain regions. The researchers also found that the brain network predicted craving in a separate group of people.
“This type of study helps us understand the link between the brain and specific behaviors,” said Dustin Scheinost, associate professor of radiology and biomedical imaging at Yale and senior author of the study. “And models like this can also help us evaluate how particular brain networks may be altered in disorders.”
Vicarious pleasures, neural pathways
The pleasure one feels seeing a friend or family member receiving an award, honor, or gift is similar to that of receiving similar recognition oneself. So how does the brain distinguish between vicarious or personal experience of reward?
A new study by Yale University researchers published in the journal Neuron shows the same two brain regions are involved in processing both sensations, but at different frequencies.
“Such a dissociation within the same neural pathway implicates that there are functional ‘frequency modules’ in which distinct types of reward information are transmitted to guide social decision-making,” said Steve Chang, an associate professor of psychology and of neuroscience, member of the Wu Tsai institute and the Kavli Institute for Neuroscience at Yale, and the senior author of the study.
Chang and his team found both vicarious or experienced rewards spurred synchronous interactions between the anterior cingulate gyrus (ACCg) and the basolateral amygdala (BLA) in the brains of monkeys engaged in social decision-making. Importantly, researchers detected increased gamma frequency synchrony between the two brain regions when an animal was experiencing a vicarious reward but increased alpha/beta frequency synchrony when experiencing a direct reward. This information consistently flowed from ACCg to BLA in all experiments conducted.
Intriguingly, this neural synchrony was observed when a monkey made a prosocial gesture resulting in an award to another monkey, but not when a computer chose an award to another monkey. “The precise way in which brain areas interact seemed to distinguish between personal and vicarious experience of reward arising from a prosocial act,” Chang said.
The mental health/physical frailty connection
Physical frailty — indicated in part by slow walking speed, persistent exhaustion, and weakness — is common among older adults and puts people at greater risk of disability and death. In a new study, Yale researchers found that frailty may be influenced by mental health and could be mediated by brain structure.
For the study, published in the Lancet Digital Health, researchers used data from nearly 500,000 middle-aged and older adults and investigated whether frailty affected other aspects of health, and vice versa. They identified 283 different health measures that are associated with frailty, with overall health, severity of depression, and health satisfaction among the strongest associations.
Among participants for whom data was available after a nine-year interval, researchers found that the severity of participants’ frailty at their initial assessment predicted decreased cognitive performance, poorer physical fitness, and increased symptoms of poor mental health.
“And we saw effects in the opposite direction too, mainly with mental health,” said Rongtao Jiang, a postdoctoral associate at Yale School of Medicine and lead author of the study. “More severe mental health symptoms at baseline were associated with more severe frailty at the nine-year follow-up.”
Next, the researchers looked at brain structure. Reduced grey matter volume and increased white matter hyperintensity are hallmarks of brain aging. In the study, researchers found that severity of frailty was linked to both. Grey matter volume and white matter hyperintensity also partially mediated the effect of frailty on other measures of health, suggesting the relationship between frailty and health could be explained, in part, by differences in brain structure.
“Our neuroimaging findings indicate a potential neurobiological basis, which deserves further investigation,” said Qinghao Liang, a Ph.D. candidate in the Department of Biomedical Engineering in the School of Engineering & Applied Science and co-author of the study.
“Ultimately, these findings highlight the need for increased attention to physical frailty and the importance of early surveillance and intervention,” said senior author Dustin Scheinost, associate professor of radiology and biomedical imaging.
Waterborne pathogens in a warming world
The shores surrounding the U.S. Gulf Coast are a home to a virulent waterborne pathogen that can cause serious stomach ailments if consumed in undercooked or raw seafood and can become a deadly, flesh-eating bacteria if it enters the blood stream.
In a new study, a team of Yale scientists used 12 years of weather data and health records from the Florida Health Department to provide a sketch of optimum conditions for the spread and prevalence of Vibrio vulnificus bacteria.
Their analysis could offer a glimpse into the future.
“We are interested in predicting the effects of climate change on the emergence of waterborne pathogens and our study does suggest that warmer water and air temperatures are key factors for risk of infection and possibly severity of outbreaks,” said C. Brandon Ogbunu, assistant professor in the Department of Ecology and Evolutionary Biology (EEB) in Yale’s Faculty of Arts and Sciences and senior author of the study.
The findings were published in PLoS Neglected Tropical Diseases.
Using data from the National Oceanic and Atmospheric Administration (NOAA), the team, which was led by EEB postdoctoral fellow Andrea J. Ayala, evaluated 448 cases of Vibrio vulnificus infections reported in Florida (one of the hotspots for the pathogen in the U.S.) between 2008 and 2020. The highest rates of infection occurred from May to October and, not surprisingly, the researchers found higher air and water temperatures were associated with risk of infection. They also found higher air and water temperatures increased the risk of death from infection. Decreased wind speeds and water pressure also were linked to higher levels of infection.
“We hope that eventually we can develop a model that will help predict risk for emerging pathogens such as Vibrio vulnificus,” Ogbunu said.
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