After providing all the funding for The Brain from Top to Bottom for over 10 years, the CIHR Institute of Neurosciences, Mental Health and Addiction informed us that because of budget cuts, they were going to be forced to stop sponsoring us as of March 31st, 2013.

We have approached a number of organizations, all of which have recognized the value of our work. But we have not managed to find the funding we need. We must therefore ask our readers for donations so that we can continue updating and adding new content to The Brain from Top to Bottom web site and blog.

Please, rest assured that we are doing our utmost to continue our mission of providing the general public with the best possible information about the brain and neuroscience in the original spirit of the Internet: the desire to share information free of charge and with no adverstising.

Whether your support is moral, financial, or both, thank you from the bottom of our hearts!

Bruno Dubuc, Patrick Robert, Denis Paquet, and Al Daigen

Wednesday, 8 January 2020
The Glymphatic System: The Sewers of the Brain

As has been well established, the human brain consumes tremendous amounts of energy: about 20 to 25% of all the energy that the body uses, even though this organ accounts for only 2% of the body’’s total weight. As a result, the brain necessarily produces large amounts of waste—the equivalent of its own weight in waste every year! But this waste can be toxic to the brain itself. How the brain gets rid of this waste was long a mystery to scientists. Some thought that the brain might cleanse itself through passive diffusion of cerebrospinal fluid from the cerebral ventricles, but this seemed like a very slow waste-removal mechanism for such an active organ as the brain. It was not until 2012 that studies on mice showed that the brain has its own specific waste-removal mechanism that is faster and more efficient..

Every artery, vein and capillary in the brain is surrounded by a perivascular space defined by the extensions of the astrocytes (a type of glial cell) that completely surround these blood vessels. The cerebrospinal fluid that bathes the brain enters through the perivascular spaces surrounding its arteries and exits through the perivascular spaces surrounding its veins (see image above).

This system is called the glymphatic system, to indicate that glial cells play the same role here that the lymphatic system does in the rest of the body: draining waste from its various tissues. The reason that the glymphatic system was discovered only recently is that it cannot be seen in brains examined post mortem. It was only with the development of a method known as two-photon microscopy that scientists could view the flows of blood and cerebrospinal fluid in the brains of living animals in real time.

This recent discovery meshes perfectly with another one, discussed in a previous post in this blog: the presence of lymphatic vessels in the dura mater, one of the three meninges (membranes) surrounding the brain. This discovery also sheds light on other scientific observations, such as the fact that during sleep, the intracellular space in the brain increases by up to 60%, most likely to allow better circulation of the cerebrospinal fluid. For example, β-amyloïd protein (whose accumulation seems to be connected with Alzheimer’s disease) appears to be removed from the brain two times more efficiently when mice are asleep than when they are awake.

And that is only one example of the protective roles that sleep plays. In recent years, scientists have developed impressive data on how sleep helps to protect the organism from a great many different pathologies.

From the Simple to the Complex | No comments

Monday, 25 November 2019
Three On-Line Atlases of the Human Brain

This week I want to tell you about three different on-line atlases of the human brain. All three will let you satisfy your curiosity by exploring the inmost recesses of the most complex object in the known universe, of which each of us has an example right between our ears. So stand warned: this post may well leave you spending even more time on your computer than usual!

First there is the Whole Brain Atlas, by Keith A. Johnson and J. Alex Becker,which has already been around for a while. On the home page, under the heading Normal Brain, the first topic is Normal Anatomy in 3-D with MRI/PET (Javascript). Here alone, you can have hours of fun clicking on the little black-on-yellow directional arrows to explore successive slices of the brain in the transaxial, sagittal and coronal planes. Often, you’ll see a large yellow arrow pointing at the specific brain structure whose name appears in the drop-down list box below the image, to the left. But you can also explore the other way around: click on the arrow in this list box to display a list of brain structures, then choose the one you’d like to view. An image of this structure then appears, with a big yellow arrow pointing at it.

Other topics in the Normal Brain section, such as Top 100 Brain Structures and Can you name these brain structures?, are designed to let you have fun while learning brain anatomy. The other main subject headings on the home page let you explore numerous images of abnormal brains, such as the brains of people who have had strokes or have brain tumours or various degenerative, inflammatory or infectious brain diseases.

The second, similar atlas is the University of Chicago MRI Brain Atlas. The page How To Use the Interactive Interface explains the symbols and abbreviations used in this atlas and the various planes of the brain sections shown in it. To access the atlas, scroll down until you see the Start Atlas button at the centre of the page, then click it. You will then probably have to click one more time to agree for your browser to use Adobe Flash. Next you will land on the home page of the atlas, but you’ll still have a few steps to go. You must click the Start button to the lower right to choose which of the axial, coronal or sagittal sections you want to explore, and then choose between two major regions of the brain. Only then will you see a list of sections, with strange names such as CO35-COD50. Once you click the name of the section that you’re interested in, an image of it will appear at last. But the effort will have been worth it: the presentation is impeccable, and you can make the names of the visible brain structures appear one by one by clicking the lines pointing to them. Or you can make them all appear or disappear at once.

The third and last atlas that I want to mention is the Big Brain, published in June 2013, It is part of the Human Brain Project and was produced by an international team of neuroscientists from the Montreal Neurological Institute in Canada and the Forschungszentrum Jülich in Germany. These researchers sliced, scanned, and analyzed the brain of a deceased 65-year-old woman to create a detailed 3D computer model of an entire human brain. Thus, unlike the two other atlases, which consist of images of sections of living people’s brains, captured by magnetic resonance imaging (MRI), this one consists of coloured sections of a person’s brain post mortem. Compared with the MRI images, whose resolution is only 1 cubic millimetre, the images in the Big Brain were made from 7400 slices of the brain, each only 20-µm thick, thus enabling 50 times greater resolution. It took the team 1000 hours to image all of these slices with a scanner, thus generating the 1 billion billion bytes of data that they used to construct their 3D model. You can explore it by using your mouse wheel to zoom in and out on every image.

From the Simple to the Complex, Uncategorized | No comments

Tuesday, 22 October 2019
Why forgetting can save your life

When we think about human memory, it tends to be with the implicit assumption that more is always better. But more and more neurobiologists are now asserting the opposite: that forgetting makes us more efficient! This raises two important questions: 1) forgetting what? and 2) more efficient in doing what? Science blogger Tom Siegfried attempts to provide the answers in an article published in January 2019, entitled “Why forgetting may make your mind more efficient.” (more…)

Memory and the Brain | No comments

Friday, 4 October 2019
Karl Friston: toward a grand unifying theory of life and cognition?

This week I’d like to tell you about a fascinating piece of reporting by journalist Shaun Raviv, in the November 13, 2018 issue of Wired magazine. It’s about one of the most important figures in the cognitive sciences today: Karl Friston. I call Raviv’s piece reporting rather than an interview because he spent more than a week in London in the summer of 2018 researching it. Its title, “The Genius Neuroscientist Who Might Hold the Key to True AI”, might seem sensationalistic, since we all know what a buzzword artificial intelligence has become. But in fact, this title understates the case. As Raviv puts it, “Friston believes he has identified nothing less than the organizing principle of all life, and all intelligence as well.”

What Friston offers is the kind of (very) grand unifying theory that doesn’t come along in science every day. But who is this guy with such big ideas? (more…)

From the Simple to the Complex | No comments

Wednesday, 28 August 2019
Shifting Paradigms in the History of Neuroscience

   The development of a scientific discipline over time is often far from a linear sequence of events that build on each other logically. That can happen, of course. But philosophers of science, such as Thomas Kuhn, have clearly shown that “normal science” often operates under a dominant paradigm for an extended period, until enough “abnormal data” (i.e., data that contradict that paradigm) accumulate to lead to a scientific revolution, accompanied by a radical shift in that paradigm.

One of these revolutions, famous in history and entertainingly presented in the Neurohistory Cartoons Project, broke out when the 1906 Nobel Prize in Physiology/Medicine was awarded jointly to Italian scientist Camillo Golgi and Spanish scientist Santiago Ramón y Cajal. (more…)

From the Simple to the Complex | No comments