Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Decision-making in the fly brain

21.08.2015

When food smells simultaneously appealing and repulsive, the learning centre aids decision-making

For most of us, a freshly brewed cup of coffee smells wonderful. However, individual components that make up the fragrance of coffee can be extremely repulsive in isolation or in a different combination. The brain therefore relativizes and evaluates the individual components of a fragrance. Only then is an informed decision possible as to whether an odour and its source are “good” or “bad”. Scientists from the Max Planck Institute of Neurobiology in Martinsried have discovered how conflicting smells are processed in the mushroom body of the brain of the fruit fly. The results assign a new function to this brain region and show that sensory stimuli are evaluated in a situation-dependent context. In this way the insects are able to make an appropriate decision on the spur of the moment.


Nerve cells that use dopamine as a neurotransmitter (green) enable hungry flies to ignore danger signs and modulate their innate behaviour.

© MPI of Neurobiology/ Friedrich

Most sensory impressions are complex. For example, a fragrant substance usually appears in combination with many other odours - like the smell of the aforementioned cup of coffee, which consists of over 800 individual odours, including some unpleasant ones. For the fruit fly Drosophila, the smell of carbon dioxide (CO2) is repellent. Among other things, the gas is released by stressed flies to warn other members of the species. When the insects smell CO2 an innate flight response is triggered. However, CO2 is also produced by overripe fruit – a coveted source of food for many insects. Foraging flies must therefore be able to ignore their innate aversion to CO2 in instances where the gas is present in combination with food odours. It is still poorly understood how the brain compares individual olfactory sensations and classifies them according to the situation at hand in order to reach a sensible decision (here: food or danger).

“The opposing significance of CO2 for fruit flies is an ideal starting point to explore how the brain correctly evaluates individual sensory impressions depending on the situation,” says Ilona Grunwald Kadow. Together with her team at the Max Planck Institute of Neurobiology, she studies how the brain processes odours and makes decisions based on the results. The scientists have now been able to show that complex or opposing sensory information is processed in the mushroom body. Until now, this brain area was thought to be a centre for learning and memory storage. The new results show that the mushroom body has an additional function: it evaluates sensory impressions independently of learned content and memory to allow instantaneous decisions.

The scientists were able to show that CO2 activates neurons in the neural network that includes the mushroom body. Those neurons, in turn, trigger the flies’ flight behaviour. However, if CO2 occurs along with food odours, the food odour stimulates neurons within the mushroom body network that release the neurotransmitter dopamine. Dopamine occurs in many species, including humans, in connection with positive values. When food smells are present along with CO2, these dopaminergic neurons in fruit flies transmit this information to the mushroom body, where they suppress the innate CO2 response by inhibiting “avoidance neurons”.

“Interestingly, the experience that CO2 frequently occurs together with food odours does not cause the insects to lose their aversion to CO2 forever,” says Grunwald Kadow. When the information about the simultaneous occurrence of CO2 and food odours is transmitted to the “learning centre” in the mushroom body, an immediate change of behaviour occurs, but not a permanent change with regard to the negative evaluation of CO2. This could apply to other sensory impressions as well, such as vision. The researchers speculate that the absence of a permanent change in behaviour could be vital in many situations. The smell of predators, for example, triggers an instinctive fear in humans. We do not lose this fear, even after experiencing caged predators and their smell at a zoo. The human brain therefore also appears to compare and draw different conclusions depending on the circumstances.


Contact

Dr. Stefanie Merker
Max Planck Institute of Neurobiology, Martinsried
Phone: +49 89 8578-3514

Email: merker@neuro.mpg.de


Dr. Ilona Grunwald Kadow
Max Planck Institute of Neurobiology, Martinsried
Phone: +49 89 8578-3159

Fax: +49 89 8578-3152

Email: ikadow@neuro.mpg.de


Original publication
Laurence P.C. Lewis, K.P. Siju, Yoshinori Aso, Anja B. Friedrich, Alexander J.B. Bulteel, Gerald M. Rubin, Ilona C. Grunwald Kadow

A higher brain circuit for immediate integration of conflicting sensory information in Drosophila

Current Biology, online 20 August, 2015

Dr. Stefanie Merker | Max Planck Institute of Neurobiology, Martinsried

More articles from Life Sciences:

nachricht Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

nachricht New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>