Welcome to The Visible Embryo

Home- - -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- News Alerts -Contact

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 ' million visitors each month.


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!



Home

History

Bibliography

Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System

Contact The Visible Embryo

News Archive
Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.
Content protected under a Creative Commons License.

No dirivative works may be made or used for commercial purposes.

Return To Top Of Page
Pregnancy Timeline by SemestersFemale Reproductive SystemFertilizationThe Appearance of SomitesFirst TrimesterSecond TrimesterThird TrimesterFetal 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 HemispheresEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterDevelopmental Timeline
Click weeks 0 - 40 and follow fetal growth
Search artcles published since 2007

October 23, 2012--------News Archive Return to: News Alerts


Head direction cells are found in many brain areas, including the (green)
post-subiculum, retrosplenial cortex, the (blue) thalamus
(the anterior and the lateral dorsal thalamic nuclei),
lateral mammillary nucleus, dorsal tegmental nucleus, striatum
and (pink) entorhinal cortex (Sargolini et al., Science, 2006).

WHO Child Growth Charts

       

How the Brain Perceives Direction and Location

How we know where we are – and where we are going, depends on cells in the brain that function to establish location and direction

The Who asked “who are you?” but Dartmouth neurobiologist Jeffrey Taube asks “where are you?” and “where are you going?” Taube is not asking philosophical or theological questions – he is investigating nerve cells in the brain that function in establishing one’s location and direction.


Jeffrey Taube is using microelectrodes
to record the activity of cells in a rat’s brain
that make possible spatial navigation
—how the rat gets from one place to another—
from “here” to “there.”

But before embarking to go “there,”
you must first define “here.”


Survival Value

“Knowing what direction you are facing, where you are, and how to navigate are really fundamental to your survival,” says Taube. “For any animal that is preyed upon, you’d better know where your hole in the ground is and how you are going to get there quickly. And you also need to know direction and location to find food resources, water resources, and the like.”

Not only is this information fundamental to your survival, but knowing your spatial orientation at a given moment is important in other ways, as well. Taube points out that it is a sense or skill that you tend to take for granted, which you subconsciously keep track of. “It only comes to your attention when something goes wrong, like when you look for your car at the end of the day and you can’t find it in the parking lot,” says Taube.

Perhaps this is a momentary lapse, a minor navigational error, but it might also be the result of brain damage due to trauma or a stroke, or it might even be attributable to the onset of a disease such as Alzheimer’s. Understanding the process of spatial navigation and knowing its relevant areas in the brain may be crucial to dealing with such situations.

The Cells Themselves

One critical component involved in this process is the set of neurons called “head direction cells.” These cells act like a compass based on the direction your head is facing. They are located in the thalamus, a structure that sits on top of the brainstem, near the center of the brain.

He is also studying neurons he calls “place cells.” These cells work to establish your location relative to some landmarks or cues in the environment. The place cells are found in the hippocampus, part of the brain’s temporal lobe. They fire based not on the direction you are facing, but on where you are located.

Studies were conducted using implanted microelectrodes that enabled the monitoring of electrical activity as these different cell types fired.


Taube explains that the two populations
—the head direction cells and the place cells—
talk to one another.

“They put that information together to give
an overall sense of ‘here,’ location wise and
direction wise,”
he says.

“That is the first ingredient for being able
to ask the question, ‘How am I going to get
to point B if I am at point A?’

It is the starting point on the cognitive map.”


The Latest Research

Taube and Stephane Valerio, his postdoctoral associate for the last four years, have just published a paper in the journal Nature Neuroscience, highlighting the head direction cells. Valerio has since returned to the Université Bordeaux in France.

The studies described in Nature Neuroscience discuss the responses of the spatial navigation system when an animal makes an error and arrives at a destination other than the one targeted —its home refuge, in this case.


The authors describe two error-correction processes
—resetting and remapping—
differentiating them based on the size of
error an animal makes when performing a task.

When an animal makes a small error
and misses a target by a little,
the cells will reset to their original setting,
fixing on landmarks it can identify
in its landscape.

“We concluded that this was an active
behavioral correction process,
an adjustment in performance
.

However, if the animal becomes disoriented
and makes a large error in its quest for home,
it will construct an entirely new cognitive map
with a permanent shift in the directional
firing pattern of the head direction cells.”
This is “remapping.”


Jeffrey Taube,
Dartmouth neurobiologist


Taube acknowledges that others have talked about remapping and resetting, but they have always regarded them as if they were the same process. “What we are trying to argue in this paper is that they are really two different, separate brain processes, and we demonstrated it empirically,” he says. “To continue to study spatial navigation, in particular how you correct for errors, you have to distinguish between these two qualitatively different responses.”

Taube says other investigators will use this distinction as a basis for further studies, particularly in understanding how people correct their orientation when making navigational errors.

Original article: http://now.dartmouth.edu/2012/10/dartmouth-researchers-explore-how-the-brain-perceives-direction-and-location/