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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

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 May 27, 2013

 
A complex set of neurochemical processes, newly unraveled, shows that obesity can sustain itself, impeding hormones that would curb appetite or increase the burn rate for calories. “This is so novel. Nobody ever looked at that possibility.”
Credit: David Orenstein/Brown University.






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'Should I stay or should I go?'

Cold Spring Harbor Laboratory scientists link brain cell types to behavior. The activity of 2 specific neuron types correlate with foraging decisions in mice

You are sitting on your couch flipping through TV channels trying to decide whether to stay put or get up for a snack. Such everyday decisions about whether to "stay" or to "go" are supported by a brain region called the anterior cingulate cortex (ACC), which is part of the prefrontal cortex. Neuroscientists from Cold Spring Harbor Laboratory (CSHL) have now identified key circuit elements that contribute to such decisions in the ACC.

CSHL Associate Professor Adam Kepecs and his team today publish results that, for the first time, link specific brain cell types to a particular behavior pattern in mice – a "stay or go" pattern called foraging behavior. The paper, published online in Nature, shows that the firing of two distinct types of inhibitory neurons, known as somatostatin (SOM) and parvalbumin (PV) neurons, has a strong correlation with the start and end of a period of foraging behavior.

Linking specific neuronal types to well-defined behaviors has proved extremely difficult. "There's a big gap in our knowledge between our understanding of neuron types in terms of their physical location and their place in any given neural circuit, and what these neurons actually do during behavior," says Kepecs.

Part of the problem is the technical challenge of doing these studies in live, freely behaving mice. Key to solving that problem is a mouse model developed in the laboratory of CSHL Professor Z. Josh Huang. The mouse has a genetic modification that allows investigators to target a specific population of neurons with any protein of interest.

Kepecs' group, led by postdocs Duda Kvitsiani and Sachin Ranade, used this mouse to label specific neuron types in the ACC with a light-activated protein – a technique known as optogenetic tagging. Whenever they shone light onto the brains of the mice they were recording from, only the tagged PV and SOM neurons responded promptly with a 'spike' in their activity, enabling the researchers to pick them out from the vast diversity of cellular responses seen at any given moment.


The team recorded neural activity in the ACC of these mice while they engaged in foraging behavior. They discovered that the PV and SOM inhibitory neurons responded around the time of the foraging decisions — in other words whether to stay and drink or go and explore elsewhere.

Specifically, when the mice entered an area where they could collect a water reward, SOM inhibitory neurons shut down and entered a period of low-level activity, thereby opening a 'gate' for information to flow in to ACC. When the mice decided to leave that area and look elsewhere, PV inhibitory neurons fired and abruptly reset cell activity.


"The brain is complex and continuously active, so it makes sense that these two types of inhibitory interneurons define the boundaries of a behavior such as foraging, opening and then closing the 'gate' within a particular neural circuit through changes in their activity," says Kepecs.

This is an important advance, addressing a problem in behavioral neuroscience that scientists call "the cortical response zoo."


When researchers record neural activity in the cortex during behavior, and they don't know which type of neurons they are recording from, a bewildering array of responses is seen. This greatly complicates the task of interpretation. Hence the significance of Kepecs' team results, for the first time showing specific cortical neurons linked to specific behaviors.


Kepecs: "We think about the brain and behavior in terms of levels; what the cell types are and the circuits or networks they form; which regions of the brain they are in; and what behavior is modulated by them. By observing that the activity of specific cell types in the prefrontal cortex is correlated with a behavioral period, we have identified a link between these levels."

"Distinct behavioural and network correlates of two interneuron types in prefrontal cortex" is published online in Nature on May 26, 2013. The authors are: D. Kvitsiani, S. Ranade, B. Hangya, H. Taniguchi, Z. J. Huang, A. Kepecs. The paper can be obtained online at doi:10.1038/nature12176.

The research described in this release was supported by the following grants and funding agencies: Sloan, Whitehall and Klingenstein Foundations to A.K. and the NIH NINDS (NS075531). B.H. received support from the Swartz Foundation and Marie Curie International Outgoing Fellowship within the EU Seventh Framework Programme for Research and Technological Development (2007-2013). D.K. received support from The Robert Lee and Clara Guthrie Patterson Trust Postdoctoral Fellowship and Human Frontier Science Program (2008-2011).

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 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. Tens of thousands more benefit from the research, reviews, and ideas published in journals and books distributed internationally by CSHL Press. The Laboratory's education arm also includes a graduate school and programs for undergraduates as well as middle and high school students and teachers. CSHL is a private, not-for-profit institution on the north shore of Long Island. For more information, visit http://www.cshl.edu.

Written by: Edward Brydon Ph.D., Science Writer