Monday, 9 March 2026
Two different levels of analysis: the hippocampus at the neuronal level and autism at the molecular level
This week, I’ll address two different topics from the angle that is so central to my website and my book about the human brain: the various levels at which the human brain and the human mind are organized. My first topic today is how the neurons of the hippocampus are affected by chronic stress. The second is how the lower availability of a certain type of neurotransmitter receptor in widespread regions of the brain may contribute significantly to traits of autism.
* * *
Sometimes, day-to-day stress can stretch out over weeks, months or even years. Such chronic stress places us in a state of what French neurobiologist Henri Laborit called “action inhibition “. Let me explain. Our human brains originally evolved to react to sudden physical threats by preparing our bodies to either fight them or run away from them. But in today’s world, many of the threats that we face are essentially verbal and occur in family or work settings where we can neither fight nor flee. Instead, we do nothing about these threats and hope that they will pass. When instead they persist, so do our ingrained physiological responses, for longer than they were ever meant to, thus causing harm to both our bodies and our brains.
As has long been known, one of the parts of the brain that are most strongly affected by chronic stress is the hippocampus, an ancient structure that is located in the medial temporal lobe and is involved in spatial declarative memory. The website Better Brain, which I discovered recently, regularly posts superb graphics about various aspects of the brain on its Facebook page, including the one reproduced above, about the effects of glucocorticoids (stress hormones) on the neurons of the hippocampus. This single image provides a great summary of an article entitled “Brain trauma, glucocorticoids and neuroinflammation: Dangerous liaisons for the hippocampus”, published in the journal Biomedecines in 2022. This image shows at a glance how the glutocorticoid corticosterone alters the functioning of the hippocampus by stimulating or inhibiting some of its neurons, resulting in excessive activity of the hippocampus as a whole. (Just one small criticism of this graphic: it shows the excitatory effects in red and the inhibitory effects in blue, whereas the usual convention is actually the reverse.)
* * *
The other topic that I wanted to tell you about today comes from an article published in the American Journal of Psychiatry in December 2025, entitled “Imaging Metabotropic Glutamate Receptor 5 and Excitatory Neural Activity in Autism. The title of the press release about this article in Neuroscience News is far more straightforward and maybe goes too far: Missing Brain Receptor May Hold the Key to Autism. Let’s set aside the idea that any single “key” can explain such a complex phenomenon as autism or the autism spectrum. But the discovery reported in this article is still interesting, because it shows that the brains of people with autism have fewer of a certain type of receptors for glutamate, the most widespread neurotransmitter in the brain. The lower availability of these receptors may be associated with various traits of autism. It is also compatible with the theory that an imbalance in the excitatory and inhibitory signals passing between neurons may contribute to the symptoms of autism, which is what makes this study’s findings of interest. I will also add in passing that this study again confirms the inextricable links among what happens at the molecular, cellular, psychological and behavioural levels in all animals.
Mental Disorders | Comments Closed
Friday, 9 January 2026
Migration of the website from thebrain.mgill.ca to thebrain.lecerveau.ca
In December 2025, I migrated my website The Brain from Top to Bottom from www.thebrain.mcgill.ca to www.thebrain.lecerveau.ca. (If you have visited the site since then, you may not even have noticed, because if you type the old address into your browser, you are now redirected to the new one automatically, and that new address appears in the browser’s address bar.) At the same time, I migrated the French version of this site, Le cerveau à tous les niveaux, from www.lecerveau.mcgill.ca to www.lecerveau.ca. Here too, if you now type the old address, you will be directed to the new one automatically. The main reason that I made these moves is that the McGill University server that used to host this site was constantly being updated with new security and other features that were highly complex and incompatible with this site as I had originally designed it. In this post, I want to share the history behind my decision to migrate these sites. (more…)
From the Simple to the Complex | Comments Closed
Friday, 31 October 2025
A visit to a hyperscanning laboratory
Last September, thanks to doctoral student Anne Monnier, I had the chance to visit the laboratory where she is doing her research, directed by Guillaume Dumas at the CHU Ste-Justine research centre in Montreal. I have written about Dumas in an earlier post in this blog, in which I described the hyperscanning technique being used for several research projects at this “precision psychiatry and social physiology” laboratory. (more…)
From Thought to Language, Mental Disorders | Comments Closed
Monday, 19 May 2025
Why does your brain consume so much energy?
Your brain accounts for only about 2% of your body weight, but 20 to 25% of all the oxygen and glucose that your body consumes. Why this vast disparity? Until about 20 years ago, people tended to think of the brain as an organ that waited passively for stimuli and then reacted to them. But more recent neuroscientific research paints a very different picture of the brain, as an organ constantly engaged in intrinsic, spontaneous activity. Metaphorically, people used to imagine the brain as a calm, flat body of water, onto which a drop of rain occasionally fell and created a few ripples. Now scientists have shown us that the brain is a place where it is always raining, so that when one drop of rain falls, the small disturbance that it creates merges into something larger that is already highly active.
This major paradigm shift originated in the observation that the brain generates neural activity patterns spontaneously, regardless of what is happening in the individual’s environment. In your earliest stages of development, you may see no apparent connection between these patterns and the world around you. But they become more meaningful as you grow, acquire experience and begin to see how your actions in certain situations affect the world around you.
From the Simple to the Complex | Comments Closed
Wednesday, 23 April 2025
Our two ways of thinking and the inhibition of the frontal cortex
The human brain is often described as having two main ways of thinking: one of them fast, automatic and unconscious, the other slower, more flexible and requiring conscious control. Each of them has its own benefits and drawbacks. The first—let’s call it “System 1”—is based on the sum of the habits, stereotypes and received ideas that we have acquired since childhood. System 1 doesn’t provide us with any ready-made solutions, but instead sends us down paths to possible or likely ones. In contrast, System 2, with its logical, rational thinking, is slower and more careful. It proceeds by deduction, inference and comparison. System 2 is what lets us see past our conditioning and beyond appearances. (more…)
From Thought to Language | Comments Closed
