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

Friday, 14 July 2017
Metaphors for the Brain’s Anatomy and Functioning

When I’m making presentations about the human brain to live audiences, the quick, easy method I often use to show them a three-dimensional model of a brain synapse is to hold my two fists facing each other, very close together, but not touching. One fist thus represents the axon of the pre-synaptic neuron, while the other represents a dendritic spine on the post-synaptic neuron. This macro model of a synapse is about 20 centimetres long.

In comparison, a real synapse in a mammalian brain is about 1 micron (one thousandth of a millimeter) long. This estimate includes the terminal button (the swelling at the tip of the axon), the dendritic spine (the swelling on a dendrite of the second neuron which receives the connection from the axon of the first), and the synaptic gap (the space between them). Into this gap, the axon of the pre-synaptic neuron releases its neurotransmitters, which immediately bind to the receptors in the membranes of the post-synaptic neuron’s dendritic spine.

To extend the metaphor, let’s say that an actual human brain is about 20 centimetres long. So, pop question: if the model synapse composed of my fists is about 20 centimetres long, how long would a model of the entire brain be on that same scale? The answer: 0.2 m x 0.2 m / 0.000 001 m = 40 000 m = 40 km! In other words, approximately the length of Montreal Island, where I live, in Quebec. (Not one to shrink from a PhotoShop challenge, I created the little set of photos above to let you visualize this metaphor more easily.)

Moving on from the anatomical size of the brain, we need some other metaphor to represent the complexity of its incessant electrical activity. There are about 85 billion neurons in the human brain, each of which can receive up to 10,000 synapses. Thus, in a matter of milliseconds, electrical impulses travel across literally trillions of synaptic connections in the brain.

The best metaphor that I have found for this incredibly complex electrical flow comes from Sebastian Seung, who studies the human connectome on the microscopic scale. He likens the brain.s electrical flows to a stream rushing through a forest. Just like the configurations of the brain’s electrical activity, the flow patterns in the water are never the same from one moment to the next. But they do reveal some “strange attractors”—eddies whose general shape is the same at certain locations, behind certain rocks. Similarly, the large networks in the human brain are connected by hubs that, though never entirely the same, can be recognized in certain situations.

The beauty of this metaphor is that it also depicts phenomena occurring on two different time scales. Just as the water’s flow is constrained by the shape of the underlying stream bed, the electrical flows in the brain are constrained by the major neural pathways that were laid down as the human brain evolved from that of other species. But on a far shorter time scale, if you go back and visit the same stream after just a few years, the current will have eroded its banks and moved some rocks around in the stream bed. And that’s exactly like what happens in your own brain in the course of a lifetime: all that constant neural activity causes permanent changes in the configuration of its neural networks, so that you are always a slightly different person from one day to the next.

From the Simple to the Complex | No comments

Tuesday, 23 May 2017
Two “Trees of Life”

This week I want to tell you about two great websites for learning about the genealogy of every living thing on planet Earth. The first is the evogeneao Tree of Life Explorer, and it uses an incredibly ingenious design that lets you click on any currently living species and trace back to the common ancestor that humans share with it. An animation then shows you where this common ancestor is located in the phylogenetic tree of all living things and tells you how many years ago this common ancestor lived. (more…)

Evolution and the Brain | No comments

Tuesday, 9 May 2017
Protect Your Immune System by Refusing To Be Dominated!

A study published in the November 25, 2016 issue of the journal Science shows that subordinate status in a social group seems to have harmful effects on an individual’s immune system. More specifically, this study found that a female rhesus monkey’s relative position in her group’s dominance hierarchy influenced the functioning of her immune system in the following way: the lower her rank, the fewer immune cells of a certain type her body produced.

And such differences seem to be caused by the activation or non-activation of certain genes. The study’s authors found that when they used experimental manipulations of the group to change individuals’ ranks in the hierarchy, the rate of expression of these genes changed as well. (more…)

Mental Disorders | No comments

Thursday, 20 April 2017
Learning Empathy

The existence of empathy and altruistic behaviour among various species of animals has been amply demonstrated. Among elephants, examples include comforting members of the herd who are frightened, rescuing others when they get get stuck in mud holes, and adopting orphaned babies. Chimpanzees and bonobos display sophisticated altruistic behaviours in dealing with weak or disabled members of their troops, trying to help them stand, bringing them food, and covering them with vegetation after confirming that they have died.

The human species is no exception. We human beings depend so much on one another and our societies are so complex that our ability to put ourselves in someone else’s shoes, to feel what they are feeling and to act accordingly, is quite obvious. Ethologists and evolutionary biologists agree that in species that form complex societies in which cooperation and mutual assistance constitute an advantage for the entire group, empathy developed naturally. (more…)

Pleasure and Pain | No comments

Thursday, 23 March 2017
When You Come Into a Room and Forget What You Were Going To Do There

Of all the psychological effects that have been given specific names (the placebo effect, the McGurk effect, the Coolidge effect, etc.), the “doorway effect” is one of the most familiar and yet also one of the most surprising. We have all experienced it: you’re at home, you go from one room into another, and then you forget what you were planning to do there!

As the first article linked to below notes, the French poet Paul Valéry once said that the purpose of psychology is to give us a completely different idea of the things we know best. In this sense, the doorway effect might be considered a perfect example of the kinds of phenomena that psychologists study. (more…)

Memory and the Brain | No comments