Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The architecture of odor perception: Olfactory glomeruli have a unique structure

21.09.2016

Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now quantified and mapped the functional units of the olfactory center in the brains of vinegar flies responsible for the perception of odors. They found out that the so-called olfactory glomeruli in the antennal lobe, the insect analogue of the olfactory bulb of mammals, differ from each other in their architecture. The morphology and the structure of these spherical brain units provide information about the ecological relevance of the odors they process, especially with regard to the flies’ odor-guided behavior.

When insects search for food, a sexual mate or the ideal place for laying eggs – somewhere where the hatching larvae have a good chance to survive – they have to rely on their sense of smell. They use their olfactory organs, the antennae, to detect odor molecules in their environment.


Fluorescence-microscopic image of the antennal lobe, the olfactory center, of the vinegar fly (Drosophila melanogaster): The spherical structures are the olfactory glomeruli.

Veit Grabe / Max Planck Institute for Chemical Ecology

These odors are processed in the so-called antennal lobe, the actual olfactory center of the insect brain, which consists of spherical structures: the olfactory glomeruli. Here, inside the olfactory glomeruli, different groups of olfactory neurons form conjunctions or synapses which enable different environmental odors to be processed.

Until now, scientists had assumed that olfactory glomeruli share a pretty homogeneous architecture and that particular functions of the different glomeruli can be attributed primarily to special olfactory receptors on the membranes of the olfactory sensory neurons.

A research team of the Department of Evolutionary Neuroethology has now shown for the first time that the neuronal composition of each glomerulus is unique and highly specific. “Each glomerulus processes different odors in a unique way. The odors, on the other hand, differ in their impact on the behavior of the vinegar flies,” explains Silke Sachse, the leader of the study.

The researchers scrutinized the neuronal architecture of the olfactory glomeruli in the vinegar fly Drosophila melanogaster and linked the morphological differences they observed to the respective functions. They labeled different neurons in single glomeruli, and counted and anatomically described these. In order to achieve this, they used transgenic Drosophila lines which expressed the photoactivatable green fluorescent protein (PA-GFP) in the neurons and high-resolution confocal microscopy.

“As assumed, but until now not experimentally proven, glomeruli which contained many olfactory sensory neurons were generally bigger than were the glomeruli with fewer olfactory sensory neurons. This means that the anatomical shape of a glomerulus already provides information about how sensitive it will respond to a certain odor,” Veit Grabe, one of the first authors of the study, reports. The scientists also investigated whether there were any differences between male and female flies: Glomeruli which processed the Drosophila sex pheromones were bigger in males which were able to perceive the female attractants from large distances.

Moreover, the researchers counted the so-called projection neurons which are responsible for the transmission of odor stimuli to higher regions of the olfactory system. Glomeruli containing highly specific olfactory sensory neurons – namely, those which process only one single odor – seem to exhibit more projection neurons than glomeruli which process many different odors. More projection neurons make sure that information is transferred to higher brain regions in a faster and more reliable way to result in rapid odor-guided decisions.

In order to link the morphology of a glomerulus to its function, the research team determined another important parameter by means of electrophysiological analysis: “Lifetime sparseness” indicates how many different odors can activate an olfactory receptor. If a receptor is activated by a large variety of odors, it has very low “sparseness” and is therefore a very broad-range receptor. The higher the “sparseness” of a receptor, the fewer odors it is able to perceive.

An extreme case would be a highly specific receptor which responds only to a single odor. Odors which are very attractive to vinegar flies include their own pheromones, but also odors which provide clues about where to find a food source, such as overripe fruit. Some of these attractive odors may elicit oviposition in females, because they provide information about a place where larvae can hatch and have a good chance to survive. However, important odors may also be deterrents – and warning signals – because they contain information about lethal dangers, such as toxic substances in a potential food source or parasites.

“The complete quantitative mapping of all olfactory sensory neurons linked together in each olfactory glomerulus helped us to create an extended morphological basis for a better understanding of the role and function these units in the olfactory system have,” co-author Amelie Baschwitz summarizes.

Because these new insights are not limited to the vinegar fly, and may also apply to other animals or even humans, they have far-reaching significance. [KG/AO]

Original Publication:
Grabe, V., Baschwitz, A., Dweck, H. K. M., Lavista-Llanos, S., Hansson, B., Sachse, S. (2016). Elucidating the neuronal architecture of olfactory glomeruli in the Drosophila antennal lobe. Cell Reports. DOI: 10.1016/j.celrep.2016.08.063
http://dx.doi.org/10.1016/j.celrep.2016.08.063

Further Information:
Dr. Silke Sachse, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Tel. +49 3641 57-1405, E-Mail ssachse@ice.mpg.de

Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail overmeyer@ice.mpg.de

Download high-resolution images via http://www.ice.mpg.de/ext/downloads2016.html

Weitere Informationen:

http://www.ice.mpg.de/ext/index.php?id=evolutionary-neuroethology&L=0 Department of Evolutionary Neuroethology

Angela Overmeyer | Max-Planck-Institut für chemische Ökologie

More articles from Life Sciences:

nachricht Seeing on the Quick: New Insights into Active Vision in the Brain
15.08.2018 | Eberhard Karls Universität Tübingen

nachricht New Approach to Treating Chronic Itch
15.08.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Unraveling the nature of 'whistlers' from space in the lab

15.08.2018 | Physics and Astronomy

Diving robots find Antarctic winter seas exhale surprising amounts of carbon dioxide

15.08.2018 | Earth Sciences

Early opaque universe linked to galaxy scarcity

15.08.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>