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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.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




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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 Feb 4, 2014


The arcuate fasciculus anterior (green) is a neural pathway connecting brain regions often used for arithmetic.
A positive correlation was found between the quality of the white matter sheathing the pathway and
proficiency in adding and multiplying. ©LVB.

Quality of white matter in the brain is crucial for adding and multiplying

WHO Child Growth Charts




Quality of brain white matter affects math ability

A new study has found that healthy 12-year-olds who score well in addition and multiplication have higher-quality white matter tracts. This correlation does not appear to apply to subtraction and division.

"Neural pathways are comparable to a bundle of cables. These cables are surrounded by an isolating sheath: myelin, or 'white matter'. The thicker the isolating sheath and the more cables there are, the more white matter. And the more white matter, the faster the signals are transferred," explains educational neuroscientist Bert de Smedt, lead author, and faculty of Psychology and Educational Sciences, at KU Leuven.

While the correlation between arithmetic and white matter tracts linking certain brain regions is known, very little research has been done to test this correlation in normally-developing children. Nor has previous research teased out differences in neuroactivity during different arithmetic operations, such as adding, subtracting, multiplying and dividing.

In this study, researchers had 25 children solve a series of different arithmetic operations while undergoing a brain scan. They then compared the quality of the children’s white matter tracts with their arithmetic test performance. ‘Grey’ cells process information in the brain and are connected via neural pathways, tracts, through which signals are transferred.

"We found that a better quality of the arcuate fasciculus anterior – a white matter tract that connects brain regions often used for arithmetic – corresponds to better performance in adding and multiplying, while there is no correlation for subtracting and dividing.”

“A possible explanation for this is that this white matter bundle is involved in rote memorization, whereas when we subtract and divide, such memorization plays less of a role. When subtracting and dividing we are more likely to use intermediary steps to calculate the solution, even as adults."

Bert De Smedt, lead author, professor of Psychology and Educational Sciences, KU Leuven.

Memorization Helps

These findings also reveal the link between reading and arithmetic, explains Professor De Smedt: "Reading proficiency and arithmetic proficiency often go hand-in-hand. The white matter tract that we studied also plays an important role in reading: when we learn to read, we have to memorize the correspondence between particular letters and the sound they represent.

"It is likely that a similar process occurs for addition and multiplication. Just think of the notorious times-table drills we all memorized as schoolchildren; it is almost like learning a nursery rhyme. Some of us can even auto-recall these sums."

"This also might explain why we often see arithmetic problems in children with dyslexia. Likewise, children with dyscalculia often have trouble reading," says Professor De Smedt.

Researchers now aim to explore how these results relate to children with impairments such as dyscalculia or from head trauma. In a next step, the team will investigate how white matter tracts can be strengthened through extra arithmetic training.

The study "Left fronto-parietal white matter correlates with individual differences in children's ability to solve additions and multiplications: A tractography study" by Leen Van Beek, Pol Ghesquière, Lieven Lagae and Bert De Smedt is published in the journal NeuroImage.

Functional neuroimaging data have pointed to the activation of a fronto-parietal network during calculation tasks, the activity of which is modulated by arithmetic operation and arithmetical competence. As the cortical brain regions of this network are distant, it is crucial to investigate the white matter connections between them and to examine how these connections are related to different arithmetic operations and individual differences in arithmetical competence. By using diffusion tensor imaging (DTI) tractography in eighteen 12-year-olds, we tested whether white matter pathways connecting these distant regions were related to children's arithmetical competence and how this association was modulated by operation. For each child, we delineated the three subcomponents of the arcuate fasciculus, a bundle of pathways linking frontal and temporo-parietal regions that are commonly active during calculation tasks. Fractional anisotropy in the left anterior portion of the arcuate fasciculus was positively correlated with addition and multiplication, but not with subtraction and division, suggesting a specific role of this left anterior segment in the solution of those problems that are expected to be solved with fact retrieval. The observed correlation was not explained by age, intelligence and working memory. Follow-up control analyses using different types of reading measures revealed that the observed correlation only disappeared when measures that draw heavily on phonological processing, such as non-word reading, were controlled for, suggesting that the association between the left arcuate fasciculus-anterior and addition/multiplication reflects the involvement of phonological processing. These results are the first to demonstrate that individual differences in fronto-parietal white matter are associated with arithmetical competence in typically developing children of a very narrow age range and indicate that this association is modulated by arithmetic operation.

• Is fronto-parietal white matter correlated with arithmetic skill?
• Diffusion tensor imaging tractography is used to examine this issue.
• The arcuate fasciculus was delineated as region of interest.
• Fractional anisotropy in left arcuate fasciculus-anterior is linked to arithmetic.
• This association is modulated by arithmetic operation.

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