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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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The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
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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 Dec 17, 2013

 

Several brain regions have been implicated in novelty processing, leading some
researchers to suggest that these regions represent a distributed network for novelty detection.

This network includes areas in the lateral prefrontal cortex (blue),
orbital prefrontal, anterior insular and anterior temporal cortex (red),
temporoparietal cortex (brown), medial temporal areas along the parahippocampal gyrus (including the perirhinal and posterior parahippocampal cortices, dark green),
and hippocampal formation (including the entorhinal cortex, dentate gyrus,
CA1-3 subfields and subicular complex, purple).
Other areas implicated in novelty processing (not shown) include the amygdala and the cingulate gyrus.

Image credit: Nature Reviews/Neuroscience







WHO Child Growth Charts

 

 

 

Brain waves in hippocampus may code neurons

Observing the theta-gamma oscillations — or “brain waves” — in the hippocampus of model animals, a brain region involved in learning and memory, scientists have previously determined these oscillations are associated with information processing during exploration and spatial navigation.

How information is processed and encoded in the brain is a central question in neuroscience, as it is essential for high cognitive function such as learning and memory. However, the underlying synaptic mechanisms have remained unclear.

In research published this week in the journal Neuron, postdoc Alejandro Pernía-Andrade and Professor Peter Jonas, both at the Institute of Science and Technology Austria (IST Austria), have discovered the synaptic mechanisms underlying oscillations at the dentate gyrus (main entrance of the hippocampus). Furthermore, the researchers suggest the role for these oscillations is the coding of information by the dentate gyrus principal neurons. Thus, contributing a better understanding of how information is processed in the brain.


Brain oscillations are, in fact, rhythmic changes in voltage in the extracellular space, referred to as electrical brain signals, associated with the processing of information.

These electrical signals are similar to those seen in electro-encephalographic recordings (EEG) in humans.


Pernía-Andrade and Jonas observed these oscillations in a brain region called the hippocampus of rats, and recorded oscillations using extracellular probes. To understand how oscillations are generated and which synaptic events trigger these oscillations, the researchers looked at synaptic transmission in granule cells (principal cells at the main entrance of the hippocampus) from both the extracellular (oscillations) and the intracellular perspectives (synaptic currents and neuronal firing), and then correlated the two.


They discovered that excitatory and inhibitory synapse signals contribute to different frequencies in oscillations.

Excitation from the entorhinal cortex generates theta oscillations — whereas inhibition by local dentate gyrus interneurons generate gamma oscillations. Together, excitation and inhibition provides the rhythmic signals of oscillations.

It is speculated that oscillations may help the dentate gyrus encode information by
“phase locking” oscillations.


The precise, high-resolution recording taken from granule cells needed for these discoveries was made possible through technological innovations by Pernía-Andrade and Jonas. Previously, no equipment was available to record synaptic signals in active rats in such high resolution.

Pernía-Andrade and Jonas worked in collaboration with Todor Asenov, manager of the Miba machine shop, IST Austria’s electrical and mechanical SSU (Scientific Service Unit). Together, they produced the first tools for precise biophysical analysis in active rats by adapting commercially available equipment as well as custom-designing tools specific to the experiments. This research is therefore not only a scientific advance but also represents a significant technological and conceptual progress in the quest to understand neuronal behavior under natural conditions.

Abstract
Highlights
Granule cells in vivo fire action potentials sparsely but often in bursts
Granule cells are exposed to barrages of fast excitatory postsynaptic currents
Granule cells receive theta-coherent excitation but gamma-coherent inhibition

Summary
Theta-gamma network oscillations are thought to represent key reference signals for information processing in neuronal ensembles, but the underlying synaptic mechanisms remain unclear. To address this question, we performed whole-cell (WC) patch-clamp recordings from mature hippocampal granule cells (GCs) in vivo in the dentate gyrus of anesthetized and awake rats. GCs in vivo fired action potentials at low frequency, consistent with sparse coding in the dentate gyrus. GCs were exposed to barrages of fast AMPAR-mediated excitatory postsynaptic currents (EPSCs), primarily relayed from the entorhinal cortex, and inhibitory postsynaptic currents (IPSCs), presumably generated by local interneurons. EPSCs exhibited coherence with the field potential predominantly in the theta frequency band, whereas IPSCs showed coherence primarily in the gamma range. Action potentials in GCs were phase locked to network oscillations. Thus, theta-gamma-modulated synaptic currents may provide a framework for sparse temporal coding of information in the dentate gyrus.

Authors
Alejandro Javier Pernía-Andradesend, Peter Jonas