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, 11 October 2017
The Brain and Body Are Really One, Especially When It Comes to Emotions

In April 2017, while preparing a lecture for a course on embodied cognition that I teach in French at UPop Montréal, I had to refresh my memory about the major communication pathways between the brain and the rest of the body, and one thing that struck me was just how many of these pathways there are!

I won’t talk here about the communication pathways that are part of the hormonal and immune systems. Instead, I’ll focus on the pathways in the nervous system alone. The central nervous system (the brain and the spinal cord) is connected to the rest of the body by the peripheral nervous system, which in turn is divided into the somatic and autonomic nervous systems. The somatic nervous system consists of the sensory nerves that carry information to the brain and the voluntary motor nerves that convey instructions from the brain to the body’s muscles. The autonomic nervous system also carries information in these two directions, to regulate the functioning of the body’s internal organs (such as the intestines, heart, and lungs). The autonomic nervous system is divided into the sympathetic and parasympathetic nervous systems. The neural pathways of the sympathetic nervous system orchestrate the flight-or-fight response to stress, while those of the parasympathetic nervous control recovery from this response.

You can find all of the above information in any book about the human nervous system. This traditional kind of functional description does of course help us to better understand the interactions between the human brain, the human body, and the outside world. But it also has the drawback of implying that the human nervous system was designed as an engineer might have done it, planning each function to provide an optimal solution to a particular problem. But that’s not how it really happened. As Nobel Prize-winning biologist François Jacob described it in his 1981 book Le jeu des possibles, “[translation] Evolution does not create something new out of nothing: it works with what already exists. The process of natural selection does not work like an engineer; it works like an artist or artisan who has no fixed plan but takes all the materials at hand and turns them into something.”

That’s why I like to discuss embodied cognition from an evolutionary perspective. To consider the importance of our bodies in our cognitive processes, we can start with the problem of the anchoring of meaning: why do some things acquire a positive or negative meaning for a given organism? The reason, as we can quickly realize from the classic example of bacteria moving up a sucrose gradient, is that the organism has a body. That body has a certain shape, certain sensory organs, and certain enzymes in its metabolism, all of which give it access to certain resources that enable it to “maintain its structure”, as Henri Laborit would say. Like any living system, this embodied organism is subject to entropy (the second law of thermodynamics), a process that tends constantly to disorganize and destroy it. The organism’s survival thus depends on behaviours of approaching resources that are useful to it—resources that its nervous system, if even slightly complex, will very quickly associate with “positive values”. Conversely, when the organism faces situations that are dangerous, that might injure or kill it, and that it hence associates with “negative values”, it must either avoid them by fleeing or, if it has no choice, fight them.

In other words, we come back to the role of the sympathetic nervous system, but this time with an ultimate, evolutionary explanation for its presence, and not just a simplistic model that treats it like a mechanism designed by an engineer.

Like cognitions, emotions are intimately connected with the body and originate in “values” that are positive or negative for the animal in question. The history of the study of emotions is full of examples of this vacillation between the relative importance of the brain and the rest of the body. From the Papez circuit to MacLean’s limbic system to the strong influences that the hypothalamus and the amygdala exert on the rest of the body, we have come now to an integrated, large-scale conception of cortical and subcortical circuits that regulate bodily processes in complex ways. This is what Luiz Pessoa proposes, for example, in an article entitled “A Network Model of the Emotional Brain” in the May 2017 edition of Trends in Cognitive Sciences.

Of course, I won’t attempt to summarize here the many studies that Pessoa refers to in his article, except to say that he puts them in perspective with major principles for the organization of brain networks, not unlike Michael Anderson’s concept of “neural reuse”. But Pessoa’s basic point is that to understand the neural bases of emotions, we must reposition them within a non-modular architecture of the brain, with a heavy overlay of networks that are highly dynamic and context-sensitive.

Emotions and the Brain | No comments

Tuesday, 26 September 2017
The Brain: The History of an Organ Like No Other

In the spring of 2017, I had to give a one-hour basic lecture about the human brain as part of a a free course for the general public at UPop Montréal. With so many different possibilities, deciding what approach to take in my lecture was no small challenge. In the end, I decided to start by trying to explain what the brain is not and dispelling a number of frequent misconceptions.

Most of the metaphors that compare the brain with a computer are pretty misleading, so I began by taking them apart, and then replacing them with others that better account for the selective, self-organizing dynamic processes that take place in the human brain and make the subtlest mental states possible. Thus, instead of comparing the brain to a computer, I used metaphors such as strange attractors in chaos physics and the complex flow patterns in a mountain stream—metaphors that can embrace both the long evolutionary history of the human brain, which accounts for its overall structure, and the neural networks that develop in an individual’s brain through a process of selection over that person’s lifetime. (more…)

From the Simple to the Complex | No comments

Monday, 21 August 2017
Humans Are the Product of Dynamic Processes on Multiple Time Scales

Today I want to talk about dynamic processes that occur on some very different time scales in the human nervous system. To do so, I will describe four examples very briefly, referring to the two graphics in this post.

The first of these processes, represented at the bottom of each graphic, is the evolution of the human nervous system, which occurs on the longest of these time scales, measured in millions of years. Over these very long periods, sexual reproduction has accelerated the diversification of our nervous systems by regularly producing variants or mutations. Some of these variants have proved capable of viable structural couplings with certain environments and have thus enabled their lucky owners to pass these nervous systems down to their descendants. I am purposely avoiding saying that these nervous systems are “better adapted to their environment”, so as not to imply that part of this environment is unchanging or that there is always some optimal level of adaptation that organisms can achieve. To state it succinctly, evolution is more proscriptive than prescriptive: it of course eliminates certain mutations that are too incapable of viable coupling with their environment, but it “allows” all the rest. (more…)

Emotions and the Brain | No comments

Thursday, 27 July 2017
The Damage Done by Social Isolation

John Cacioppo is a pioneer in the field of social neuroscience. He observes that people who are socially isolated were long thought to be suffering from some form of mental illness. But research done on this subject by Cacioppo and a number of other scientists over the past 10 to 20 years shows that social isolation is very much caused and/or aggravated by environmental factors in the broad sense, ranging from political decisions to economic ideologies. Not the least of these factors is the emphasis that our capitalist societies place on productivity. People who cannot find their place in this highly hierarchical, competitive system are too often regarded as “losers” whom an increasingly frayed social-safety network can no longer support adequately. (more…)

Mental Disorders | No comments

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. (more…)

From the Simple to the Complex | No comments