Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Appetite – it’s a brain thing

08.09.2006
The regulation of body weight and energy balance in animals depends on the central nervous system capacity to read the body’s metabolic state and respond accordingly.

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 (catarina.amorim@linacre.ox.ac.uk)

Catarina Amorim | alfa
Further information:
http://www.neuron.org/content/article/abstract?uid=PIIS0896627306005496

More articles from Health and Medicine:

nachricht Cholesterol-lowering drugs may fight infectious disease
22.08.2017 | Duke University

nachricht Once invincible superbug squashed by 'superteam' of antibiotics
22.08.2017 | University at Buffalo

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>