Summary: A new study provides insight into the areas of the brain which become activated when people are presented with aversive foods and suggests the reward circuit may encode disgust.
Until now, the reason why some people hate cheese has been a mystery. Researchers at the Centre de Recherche en Neuroscience de Lyon (CNRS/INSERM/Université Claude Bernard Lyon 1/Université Jean Monnet) and the Laboratoire Neuroscience Paris Seine (CNRS/INSERM/UPMC) have just elucidated it. Their results are published online on the Frontiers in Human Neuroscience website.
It is difficult to remain lukewarm when faced with a ripe camembert or goats cheese: people love it or hate it. France may well be the country that has the largest number of cheese varieties (almost 1600), yet many there are disgusted by it. Aversion is an extremely powerful factor in the animal world: it is a key element for survival, hence the importance of studying the cerebral mechanisms at play.
Why cheese? Because it seemed to the researchers that many people do not like this type of dairy product. Therefore they studied a sample of 332 individuals to check their intuition: cheese is indeed the food that most frequently triggers aversion. It affects 6.0% of respondents, whereas only 2.7% of those tested have an aversion to fish and 2.4% to cured meats. Among those with an aversion to cheese, 18% say they are intolerant to lactose. In 47% of cases, at least one of their family members does not like cheese either. These figures suggest that there is a genetic origin to this aversion, which might be related to lactose intolerance.
To find out what happens in the brain, fifteen people who like cheese and fifteen who do not were selected and participated in a functional magnetic resonance imaging (fMRI) study1. They were simultaneously exposed to the image and smell of six different cheeses and six other types of control foods. They had to state whether they liked the smell and sight of the foods or not, and whether, at that moment, they wanted to eat them.
The researchers then observed that the ventral pallidum, a small structure usually activated in people who are hungry, was totally inactive while the smell and image of cheese was being presented to individuals with an aversion to cheese, whereas it was activated for all other food types. Even more surprisingly, the researchers observed that areas of the brain, the globus pallidus and the substantia nigra, which participate in the reward circuit (activated when we love something), were more involved in people who do not like cheese than in those who do. These structures, typically involved in processing reward, may therefore also be triggered in response to an aversive stimulus. To explain this dual nature, the researchers suggest that these regions include two types of neurons with complementary activity: one related to the rewarding aspect of a food, the other to its aversive nature.
This work provides an insight into the areas of the brain that are activated when an individual is presented with an aversive food and suggests that the reward circuit may also encode disgust.
Source: Jean-Pierre Royet – CNRS
Image Source: NeuroscienceNews.com image is credited to Jean-Pierre Royet/Centre de Recherche en Neuroscience de Lyon.
Original Research: Full open access research for “The Neural Bases of Disgust for Cheese: An fMRI Study” by Jean-Pierre Royet, David Meunier, Nicolas Torquet, Anne-Marie Mouly and Tao Jiang in Frontiers in Human Neuroscience. Published online October 17 2016 doi:10.3389/fnhum.2016.00511
The Neural Bases of Disgust for Cheese: An fMRI Study
The study of food aversion in humans by the induction of illness is ethically unthinkable, and it is difficult to propose a type of food that is disgusting for everybody. However, although cheese is considered edible by most people, it can also be perceived as particularly disgusting to some individuals. As such, the perception of cheese constitutes a good model to study the cerebral processes of food disgust and aversion. In this study, we show that a higher percentage of people are disgusted by cheese than by other types of food. Functional magnetic resonance imaging then reveals that the internal and external globus pallidus and the substantia nigra belonging to the basal ganglia are more activated in participants who dislike or diswant to eat cheese (Anti) than in other participants who like to eat cheese, as revealed following stimulation with cheese odors and pictures. We suggest that the aforementioned basal ganglia structures commonly involved in reward are also involved in the aversive motivated behaviors. Our results further show that the ventral pallidum, a core structure of the reward circuit, is deactivated in Anti subjects stimulated by cheese in the wanting task, highlighting the suppression of motivation-related activation in subjects disgusted by cheese.
“The Neural Bases of Disgust for Cheese: An fMRI Study” by Jean-Pierre Royet, David Meunier, Nicolas Torquet, Anne-Marie Mouly and Tao Jiang in Frontiers in Human Neuroscience. Published online October 17 2016 doi:10.3389/fnhum.2016.00511