Neuron 'claws' in the brain enable flies to distinguish one scent from another

October 20, 2013
Kenyon cell claws (indicated with boxes) extend from a single cell body in the fruit fly brain. CSHL researchers have found that each claw responds to different chemical compounds, and multiple claws must be stimulated in order for the Kenyon cell to become active. In this way, the Kenyon cells are the integration point that allows the fly to "remember" a smell. Credit: Turner Lab, Cold Spring Harbor Laboratory

Think of the smell of an orange, a lemon, and a grapefruit. Each has strong acidic notes mixed with sweetness. And yet each fresh, bright scent is distinguishable from its relatives. These fruits smell similar because they share many chemical compounds. How, then does the brain tell them apart? How does the brain remember a complex and often overlapping chemical signature as a particular scent?

Researchers at Cold Spring Harbor Laboratory (CSHL) are using the fruit fly to discover how the integrates multiple signals to identify one unique smell. It's work that has broader implication for how flies – and ultimately, people – learn. In work published today in Nature Neuroscience, a team led by Associate Professor Glenn Turner describes how a group of neurons in the fruit fly brain recognize multiple individual chemicals in combination in order to define, or remember, a single scent.

The olfactory system of a fruit fly begins at the equivalent of our nose, where a series of neurons sense and respond to very specific chemicals. These neurons pass their signal on to a group of cells called projection neurons. Then the signal undergoes a transformation as it is passed to a body of neurons in the fly brain called Kenyon cells.

Kenyon cells have multiple, extremely long protrusions that grasp the projection neurons with a claw-like structure. Each Kenyon cell claw is wrapped tightly around only one projection neuron, meaning that it receives a signal from just one type of input. In addition to their unique structure, Kenyon cells are also remarkable for their selectivity. Because they're selective, they aren't often activated. Yet little is known about what in fact makes them decide to fire a signal.

Turner and colleague Eyal Gruntman, who is lead author on their new paper, used cutting-edge microscopy to explore the chemical response profile for multiple claws on one Kenyon cell. They found that each claw, even on a single Kenyon cell, responded to different chemicals. Additional experiments using light to stimulate individual (a technique called optogenetics) revealed that single Kenyon cells were only activated when several of their claws were simultaneously stimulated, explaining why they so rarely fire. Taken together, this work explains how individual Kenyon cells can integrate multiple signals in the brain to "remember" the particular chemical mixture as a single, distinct odor .

Turner will next try to determine "what controls which claws are connected," which will provide insight into how the brain learns to assign a specific mix of chemicals as defining a particular scent. But beyond simple odor detection, the research has more general implications for learning. For Turner, the question driving his work forward is: what in the brain changes when you learn something?

Explore further: The discerning fruit fly: Linking brain-cell activity and behavior in smell recognition

More information: "Integration of the olfactory code across dendritic claws of single mushroom body neurons" appears online ahead of print in Nature Neuroscience on October 20, 2013. DOI: 10.1038/NN.3547

Related Stories

The discerning fruit fly: Linking brain-cell activity and behavior in smell recognition

June 18, 2013
Behind the common expression "you can't compare apples to oranges" lies a fundamental question of neuroscience: How does the brain recognize that apples and oranges are different? A group of neuroscientists at Cold Spring ...

Study shows how neurons enable us to know smells we like and dislike, whether to approach or retreat

October 7, 2013
Think of the smell of freshly baking bread. There is something in that smell, without any other cues – visual or tactile – that steers you toward the bakery. On the flip side, there may be a smell, for instance that of ...

Neuroscientists show activity patterns in fly brain are optimized for memory storage

August 18, 2011
We know from experience that particular smells are almost inseparable in our minds with memories, some vague and others very specific. The smell of just-baked bread may trigger an involuntary mental journey, even if for a ...

A giant interneuron for sparse coding

May 13, 2011
A single interneuron controls activity adaptively in 50,000 neurons, enabling consistently sparse codes for odors.

Flies reveal that a sense of smell, like a melody, depends upon timing

April 10, 2013
(Medical Xpress)—The sense of smell remains a mystery in many respects. Fragrance companies, for instance, know it is crucial that chemical compounds in perfumes reach nostrils at different rates to create the desired sensory ...

Glowing neurons reveal networked link between brain, whiskers

October 16, 2013
Human fingertips have several types of sensory neurons that are responsible for relaying touch signals to the central nervous system. Scientists have long believed these neurons followed a linear path to the brain with a ...

Recommended for you

New study reveals contrasts in how groups of neurons function during decision making

July 19, 2017
By training mice to perform a sound identification task in a virtual reality maze, researchers at Harvard Medical School and the Istituto Italiano di Tecnologia (IIT) have identified striking contrasts in how groups of neurons ...

Memory takes time, researchers conclude

July 19, 2017
How short-term memories become long-term ones has frequently been explored by researchers. While a definitive answer remains elusive, New York University scientists Thomas Carew and Nikolay Kukushkin conclude that this transformation ...

Researchers identify new target for chronic pain

July 19, 2017
Proteins must be in the right place at the right time in the cell to function correctly. This is even more critical in a neuron than in other cells because of its complex tree-like structure and its function. Researchers ...

Brains are more plastic than we thought

July 19, 2017
Practice might not always make perfect, but it's essential for learning a sport or a musical instrument. It's also the basis of brain training, an approach that holds potential as a non-invasive therapy to overcome disabilities ...

Healthy heart in 20s, better brain in 40s?

July 19, 2017
Folks with heart-healthy habits in their 20s tend to have larger, healthier brains in their 40s—brains that may be better prepared to withstand the ravages of aging, a new study reports.

Individual insight into brain networks

July 19, 2017
Harvard scientists have gained new insights into how the brain networks important for thought and remembering are organized in individual people, bringing the notion of using brain scans to help personalize medical treatments ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.