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Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive Oct 24, 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.

Image Credit: Turner Lab, Cold Spring Harbor Laboratory







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Flies distinguish scent using neuron 'claws' in brain

The smell of an orange, a lemon, and a grapefruit, each has strong acidic scent mixed with sweetness. Yet each is distinguishable from the other. They smell similar because they share many chemical compounds. How does the brain tell them apart?

Researchers at Cold Spring Harbor Laboratory (CSHL) are using the fruit fly to discover how the brain 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 neurons (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?

Abstract
In the olfactory system, sensory inputs are arranged in different glomerular channels, which respond in combinatorial ensembles to the various chemical features of an odor. We investigated where and how this combinatorial code is read out deeper in the brain. We exploited the unique morphology of neurons in the Drosophila mushroom body, which receive input on large dendritic claws. Imaging odor responses of these dendritic claws revealed that input channels with distinct odor tuning converge on individual mushroom body neurons. We determined how these inputs interact to drive the cell to spike threshold using intracellular recordings to examine mushroom body responses to optogenetically controlled input. Our results provide an elegant explanation for the characteristic selectivity of mushroom body neurons: these cells receive different types of input and require those inputs to be coactive to spike. These results establish the mushroom body as an important site of integration in the fly olfactory system.

The research described in this release was supported by the Elisabeth Sloan Livingston fellowship from the Watson School of Biological Sciences. and the US National Institutes of Health grant R01 DC010403-01A1.

"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. The authors are: Eyal Gruntman and Glenn Turner. The paper can be obtained online at: http://dx.doi.org/ 10.1038/NN.3547

About Cold Spring Harbor Laboratory
Founded in 1890, Cold Spring Harbor Laboratory (CSHL) has shaped contemporary biomedical research and education with programs in cancer, neuroscience, plant biology and quantitative biology. CSHL is ranked number one in the world by Thomson Reuters for the impact of its research in molecular biology and genetics. The Laboratory has been home to eight Nobel Prize winners. Today, CSHL's multidisciplinary scientific community is more than 600 researchers and technicians strong and its Meetings & Courses program hosts more than 12,000 scientists from around the world each year to its Long Island campus and its China center. For more information, visit http://www.cshl.edu.

Original press release:http://www.cshl.edu/Article-Turner/neuron-claws-in-the-brain-enable-flies-to-distinguish-one-scent-from-another