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

Thursday, 16 August 2018
Human Brain Networks Operate on a Unimodal/Multimodal Gradient

This week I’d like to tell you about an article published in the journal PNAS in 2016. It is of interest because it does something that is extremely valuable in the realm of science: it shows how two bodies of data converge into a single phenomenon and thereby helps us to understand some things that were less clear before. Let me explain.

The article, by Daniel S. Margulies and no fewer than 11 co-authors, is entitled “ Situating the default-mode network along a principal gradient of macroscale cortical organization”. In slightly simpler terms, their study involved situating the brain’s default mode network along a large-scale organizational gradient within the cerebral cortex. Okay, let me explain further.

For some time, neuroscientists have known of the existence of a gradient between the more sensory parts of the cerebral cortex (the primary visual cortexes, primary auditory cortexes, and so on) and the more associative ones. One way of describing the two ends of this gradient would be to say that the more sensory end is composed of unimodal areas (whose neurons respond to stimuli from only one sensory modality) while the more associative end is composed of multimodal areas (in which the same neuron can be activated by several different sensory modalities). Yet another way to describe this distinction would be to say that one end of the gradient consists of the parts of the brain that are more involved in “online” processing (when we perceive and take action in real time) while the other consists of the parts that are more involved in “offline” processing (when we perform more abstract mental simulations without translating them into actual behaviour). In short, scientists knew that one aspect of the organization of the cortex consisted of this gradient between perception and concrete action on the one hand and abstract thought on the other, and that the latter was made possible by the disproportionate expansion of the associative cortex in the human brain.

Scientists also already knew about a number of large networks in the brain to which they assigned functional names to attempt to account for their increased activation in certain situations—for example, the visual network, the somatomotor network, the dorsal attention network, the salience network, and, perhaps most fascinating of all, the default mode network.

The default mode network was first discovered when scientists realized that all of the brain areas that form it (such as the angular gyrus, anterior cingulate cortex, posteromedial cortex, medial temporal gyrus, medial frontal gyrus and superior frontal gyrus) became active when the individual was no longer engaged in any particular task. What could a network that becomes active when you’re no longer doing anything be good for? For many things, scientists soon realized. Just because you’re not moving doesn’t mean you’re not really doing anything. You can be thinking about all kinds of things in “offline” mode: you might be recalling certain memories, or making plans for the future, or trying to understand what someone was trying to tell you, or, more broadly, trying to gain insight into other people’s mental states.

As has now been shown, the default mode network is more active in all of these situations, as well as in some more nebulous ones, such as when you’re daydreaming and making all kinds of free associations. As has also been shown recently, the default mode network may co-operate with other brain areas involved in controlling cognitive tasks that require the use of working memory. So apart from the fact that the default mode network is apparently involved in some high-level processes, there is still no consensus regarding its function.

This is where the study by Margulies et al. seems to have advanced our understanding. First, these authors have successfully confirmed the existence of a connectivity gradient (from the more unimodal regions to the more multimodal regions of the brain) that reflects structural characteristics of the brain’s anatomy with which we are already familiar (the physical position of the visual areas relative to that of the associative areas of the cortex). Second, these authors showed that the various known networks of the brain could be situated along this gradient, with the networks involved in perception and action clustered toward the more unimodal end and the networks associated with increasingly abstract cognitive functions clustered toward the more multimodal end. And can you guess which network is located farthest along this gradient of increasing abstraction? Why, the default mode network, of course.

The Margulies article makes some other interesting points as well. And I have also just learned that in January 2018, Margulies published an opinion piece on this subject in Trends in Cognitive Sciences. Once I’ve read and digested it, I’ll write another blog post to tell you what I’ve learned.

Uncategorized | No comments

Friday, 27 July 2018
Two Books on the Enactive Approach in Cognitive Science

This week, I’d like to tell you about two books on the philosophy of cognitive science. Both of them were published in 2017, and both of them deal with the enactive approach first proposed in the 1990s by pioneers such as Francisco Varela and Evan Thompson. Since then, the enactive approach has become a major research topic in contemporary cognitive science, so it is no surprise that entire books are now devoted to it.

The first of these two books is Sensorimotor Life: An Enactive Proposal, by Ezequiel Di Paolo, Thomas Buhrmann and Xabier E. Barandiaran. (more…)

Body Movement and the Brain, From Thought to Language | No comments

Wednesday, 4 July 2018
Explaining Science Not at Three Levels But at Five

This week I’d like to draw your attention to a series of videos that the U.S. magazine Wired published on YouTube in spring 2017. In each episode of this series, an expert in a particular scientific field explain a complex concept in that field to five different people: a 5-year-old, a teenager, a college student, a graduate student and a colleague who is also an expert in that field. Thus you watch the expert explain the same concept five times—from the simplest possible explanation for the 5-year-old to a high-level discussion with the colleague. This is a highly original teaching approach that you don’t see very often, except on some websites where you can drill down from a simpler explanation to a second, more advanced one, or on a certain website about the human brain that provides three levels of explanation at five levels of organization (and whose author clearly must be obsessed with levels, probably because he read too much Laborit in his youth ;-P ).

So you can understand why I couldn’t resist telling you about this web series, especially since one of the episodes deals with the connectome, a neuroscientific research topic that I have discussed previously in this blog and also teach in some of the courses that I give in French in Montreal. (more…)

From the Simple to the Complex | No comments

Tuesday, 12 June 2018
We Are Blind to Many of the Reasons for Our Conscious Choices

In a study that they conducted in 2005, entitled “Failure to detect mismatches between intention and outcome in a simple decision task”, Lars Hall and Peter Johansson uncovered a spectacular phenomenon. In this experiment, the researchers showed their subjects pairs of cards with pictures of two different people’s faces and asked their subjects to pick whichever of the two people they found more attractive. Once a subject had made this choice, the experimenter took back the cards and then, using a little sleight of hand, gave the subject back the card that he or she had not chosen and asked what it was about the person pictured that made them more attractive. Over 80% of the subjects failed to notice that they had been given the wrong card and actually provided the kind of verbal explanation requested—that it was the expressiveness of the person’s eyes or the overall harmoniousness of their features, or what have you. (more…)

From Thought to Language | No comments

Tuesday, 29 May 2018
What Chaos Physics Tells Us About the Dynamic Brain

Once upon a time, not that long ago in the history of neuroscience, the chaotic aspect of all of the brain’s neuronal oscillations was regarded as mere “background” noise. But that time is now past. The temporal dimension of brain activity, as expressed in cerebral rhythms, and the associated synchronization of neural activity, is now central to research in such complex areas as sleep and consciousness. Much of our current understanding of how the dynamic activity of the human brain can be chaotic and yet meaningful is owed to the pioneering research of Walter J. Freeman. (more…)

From the Simple to the Complex | No comments