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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 SemestersDevelopmental TimelineFertilizationFirst TrimesterSecond TrimesterThird TrimesterFirst Thin Layer of Skin AppearsEnd of Embryonic PeriodEnd of Embryonic PeriodFemale Reproductive SystemBeginning Cerebral HemispheresA Four Chambered HeartFirst Detectable Brain WavesThe Appearance of SomitesBasic Brain Structure in PlaceHeartbeat can be detectedHeartbeat can be detectedFinger and toe prints appearFinger and toe prints appearFetal sexual organs visibleBrown fat surrounds lymphatic systemBone marrow starts making blood cellsBone marrow starts making blood cellsInner Ear Bones HardenSensory brain waves begin to activateSensory brain waves begin to activateFetal liver is producing blood cellsBrain convolutions beginBrain convolutions beginImmune system beginningWhite fat begins to be madeHead may position into pelvisWhite fat begins to be madePeriod of rapid brain growthFull TermHead may position into pelvisImmune system beginningLungs begin to produce surfactant
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development


Hippocampus essential in all aspects of recognition

The hippocampus plays a major role in memory and spatial navigation. It is essential to our recognizing previous events, objects, and people - which is known as recognition memory.

New research verrifying this concept comes from the departments of Neurosurgery and Psychology in the Perelman School of Medicine at the University of Pennsylvania, and is now published in the journal the Proceedings of the National Academy of Sciences or PNAS.

Recognition memory is composed of two processes: (1) recollection which is recognizing something including vivid details of the initial encounter; and (2) familiarity, or a general sense of having previously encountered something.

Both processes often break down with aging, neurodegenerative disorders (such as Alzheimer's disease), or traumatic brain injury. The new findings provide a roadmap to guide strategies towards improving these functions.

"There's a longstanding debate in the recognition memory field about how the human hippocampus contributes to our ability to recognize.

"One segment believes that neural activity in the hippocampus contributes only to recollection, whereas some believe hippocampal activity supports both recollection and familiarity. Our study aimed to get to the bottom of this debate."

Maxwell Merkow MD, Neurosurgery Chief Resident, Hospital of the University of Pennsylvania, and lead author.

The University of Pennsylvania team hypothesizes that the hippocampus supports both recollection and familiarity. But showing a clear link between hippocampal activity and recognition memory performance has proven elusive, only having been documented in a few studies. The new paper is the first to record a link between hippocampal activity and both processes of recollection and familiarity.

Merkow and colleagues studied 66 epilepsy patients undergoing intracranial hippocampal monitoring. They administered memory tasks to the participants — asking them to remember a series of words, then showing them a second series of words, some of which they had seen before, and some that were new. Patients were then asked to determine whether or not each word had been part of the initial group.

The team recorded electrical data directly from the patient's hippocampus during the tests and were able to measure neural firings lasting mere hundreds of milliseconds, capturing activity tied to cognition - the process of acquiring knowledge.

Research found elevated high frequency hippocampal activity during trials in which patients correctly identified a word previously seen — as opposed to lower activity during trials where patients either failed to recognize a previously seen word, or saw a new word and failed to identify it as new.

A major finding was that the strength of hippocampal activity predicted behavioral performance, directly linking the hippocampus to recognition memory.

Crucially, both recollection and familiarity of recognition correlates with hippocampal activity — and both cognitive processes are supported by the hippocampus.

Merkow:  "This work directly addresses the issue of where in the brain recognition takes place. We now need to focus our efforts on how these processes occur."

The team plans to use the same high frequency recordings from smaller electrodes to address this question. Their work brings science one step closer to understanding how brain activity supports memory and potentially improving memory with "to be discovered" interventions.

Recognition memory is thought to be composed of recollection, accompanied by vivid details, and familiarity or a general sense of knowing. A fundamental and long-standing question remains: Which of these processes does the hippocampus support? We measured high-frequency activity (HFA), a spatiotemporally precise signal of neural activation, in subjects undergoing direct brain recordings and found that hippocampal HFA dissociated based on both the stimulus evidence presented and the response choice. Hippocampal HFA predicted overall memory performance as well as individual differences in both recollection and familiarity estimates. Our findings reject the hypothesis that the hippocampus exclusively supports the recollection component of recognition memory and, instead, indicate that this structure is functionally relevant to both processes thought to support recognition.

Despite a substantial body of work comprising theoretical modeling, the effects of medial temporal lobe lesions, and electrophysiological signal analysis, the role of the hippocampus in recognition memory remains controversial. In particular, it is not known whether the hippocampus exclusively supports recollection or both recollection and familiarity—the two latent cognitive processes theorized to underlie recognition memory. We studied recognition memory in a large group of patients undergoing intracranial electroencephalographic (iEEG) monitoring for epilepsy. By measuring high-frequency activity (HFA)—a signal associated with precise spatiotemporal properties—we show that hippocampal activity during recognition predicted recognition memory performance and tracked both recollection and familiarity. Through the lens of dual-process models, these results indicate that the hippocampus supports both the recollection and familiarity processes.

hippocampus recognition memory recollection familiarity high-frequency activity

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1513145112/-/DCSupplemental.

Additional Penn authors include John F. Burke and Michael J. Kahana

This work was supported by the National Institutes of Health (MH055687)

Penn Medicine is one of the world's leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania(founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System, which together form a $5.3 billion enterprise.

The Perelman School of Medicine has been ranked among the top five medical schools in the United States for the past 17 years, according to U.S. News & World Report's survey of research-oriented medical schools. The School is consistently among the nation's top recipients of funding from the National Institutes of Health, with $409 million awarded in the 2014 fiscal year.

The University of Pennsylvania Health System's patient care facilities include: The Hospital of the University of Pennsylvania and Penn Presbyterian Medical Center -- which are recognized as one of the nation's top "Honor Roll" hospitals by U.S. News & World Report -- Chester County Hospital; Lancaster General Health; Penn Wissahickon Hospice; and Pennsylvania Hospital -- the nation's first hospital, founded in 1751. Additional affiliated inpatient care facilities and services throughout the Philadelphia region include Chestnut Hill Hospital and Good Shepherd Penn Partners, a partnership between Good Shepherd Rehabilitation Network and Penn Medicine.

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Dec 7, 2015   Fetal Timeline   Maternal Timeline   News   News Archive   

Image Credit: Gareth J. Toner











Phospholid by Wikipedia