But how does the brain process and integrate information to regulate feeding behaviour in order to sustain the energetic needs of the organism? In an article now published on the journal "Neuron", scientists from the US and Portugal study the brain activity of rats during a feeding cycle - consisting of an episode of hunger, satiety and hunger again - and found that, while individual neurons respond to parts of the cycle, the pooled activity of the neurons in entire brain areas is always high throughout hunger, diminishing after the animal is fed and satiated, and again increases when the animal is hungry again, a variation that most probably underlies the activation of the mechanism associated with feeding motivation in these animals.
For survival, the individuals of a species have to carry vital functions such as eating, drinking, having sex or present maternal behaviour. To assure this happens, during evolution, certain areas in the brain have developed to provide strong feelings of pleasure as a “reward” for carrying out these vital functions.
A typical example is the motivation to eat, which is balanced between states of hunger - when eating is accompanied by a sensation of pleasure - and satiation - when the brain senses a biochemical change and stops the feeding process.
Previous research has shown that, during hunger, several areas in the brain seem to show increased neural activity which, after eating, is reduced. These experiments, however, were limited because, on one hand the animals were never allowed to eat freely as the food was controlled by the scientist, and on the other hand a whole cycle of hunger, satiety and new episode of hunger was never fully studied.
Trying to understand better the brain process that leads to the motivation to start and end the feeding process Ivan E. de Araujo, Sidney A. Simon and colleagues at Duke University Medical Center in North Carolina, US and at Porto University, Portugal decided to look at rats’ brain activity in a more ”natural” experimental situation – the animals were allowed to decide when to start and end eating, and their brains were analysed throughout entire hunger-satiety-hunger cycles.
The researchers measured neural activity in four brain areas known to be associated with feeding motivation - lateral hypothalamus, orbitofrontal complex, basolateral amygdale and insular cortex - during a full feeding cycle in which the rats were hungry, fed on sugary water until satiated and then grew hungry again. The activity of individual neurons within these areas was also analysed. The levels of glucose and insulin in the blood were also measured during the experiments.
By correlating the different stages of feeding (hunger - satiety –hunger) with brain activity, the researchers found that the majority of individual neurons only responded to a particular metabolic state (for example low or high glucose levels but not to both) within the full feeding cycle. By contrast, the whole activity of any of the four brain areas analysed, consistently increase during the hunger episodes and decrease during satiety allowing an accurate prediction of the duration, start and end of the different stages. These results show that the mechanism regulating feed motivation is distributed across different brain areas, forming a connected circuit that shares information on sensorial and motivational aspects of feeding collected from a multitude of individual neurons.
Araujo, Simon and colleagues also found that, from the four brain areas studied, lateral hypothalamus seemed to be the most important for eating motivation, as its neural activity had the highest correlation with the changes within the feeding cycle. This result agrees with previous observations where single lesions in this brain area can automatically lead to radical changes in appetite whether leading to hyperphagia – abnormally high food intake or, hypophagia- reduced food intake. This research contributes to a better understanding of the brain mechanic behind feeding stimulus, a particularly important issue in view of the current world epidemic of obesity.
Piece researched and written by: Catarina Amorim (firstname.lastname@example.org)
Catarina Amorim | alfa
Speed data for the brain’s navigation system
06.12.2016 | Deutsches Zentrum für Neurodegenerative Erkrankungen e.V. (DZNE)
Study suggests possible new target for treating and preventing Alzheimer's
02.12.2016 | Oregon Health & Science University
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering