Tuesday, 29 October 2024
Neuronal recycling
The concept of neuronal recycling is based on the principle that the process of evolution never starts from zero, but instead always builds on whatever has come before. In this way, the brain can develop complex new functions far more efficiently than if it had had to create them from scratch. It would be surprising if the brain didn’t take advantage of this principle, and in fact, many neuroscience researchers have developed theories and models that are based on it. Thus, brain circuits that evolved earlier—sensorimotor circuits, for example—are thought to contribute to the development of new brain functions, such as language, while still preserving their original functions as well.
Another example is that various types of neurons of the hippocampus—a brain structure associated with navigating through space—are probably reused when we form mental maps of our social networks (who among all the people I know do I feel close to? who is above or below me in the social hierarchy?). And this complex social mapping seems to be facilitated by the same areas of the hippocampus that we use to prepare mental timelines of our lives, or mental maps of our conceptual knowledge, or old-fashioned geographical maps to orient ourselves in space. And the same big advantage for the other kinds of maps applies here too: the ability to simulate possible choices and to make predictions in the comfort of our own mental space and, ultimately, to navigate our social space more easily by recycling an old mechanism for navigating through physical space.
Evolution and the Brain | Comments Closed
Tuesday, 8 October 2024
The “forest troop” : a tale of baboons about our world ?
Primatologist Robert Sapolsky studied a troop of baboons in Kenya for many years. Around the mid-1980s, the dominant males in this troop began raiding a garbage dump near a tourist lodge, where they ate meat that was infected with tuberculosis and ended up killing them. Because the most aggressive males in the troop had thus been killed off, the troop as a whole became more peaceful. There was still a hierarchy, but it had become much less rigid. This new pattern persisted even 10 to 20 years later, when all of the males then in the troop had been born in different ones (male baboons leave their natal troops and join others once they reach reproductive age). These males born in other troops had no need to be so aggressive in this especially peaceful baboon culture (until then, ethologists had always described baboons as especially aggressive animals). I wonder what might happen if all of the most aggressive, dominant men running the world’s empires today were suddenly to die from, say, eating contaminated caviar. You may laugh, but this natural experiment with baboons raises many questions about the supposedly unavoidable aspects of human societies.
Emotions and the Brain, Mental Disorders | Comments Closed
Tuesday, 17 September 2024
Spectacular reconstructions of the neurons of the human cortex
The problem with scientific research is that it never stops. Recently, my friend Jean-Pierre, who keeps a close eye on new articles in major neuroscientific journals, let me know about a major paper just published in Science, about how electron microscopy is now being used to reconstruct neurons of the human cortex with unequalled precision. And since this research had been done by Jeff Lichtman’s team at Harvard, and I had already written a post about it in this blog back in 2014 , I figured that I had better write another post about it now, because the images of neurons that this team has succeeded in producing recently are truly spectacular. For example, the image above represents one neuron with 5600 axons (blue) making synaptic connections (green)). (more…)
From the Simple to the Complex | Comments Closed
Monday, 19 August 2024
Discovery of the “jailer” in our neurons
Today I’d like to say a few words about a phenomenon that is related to neuronal plasticity and that I’d never heard of before. I learned about it in a book entitled Seeing the Mind: Spectacular Images from Neuroscience, and What They Reveal about Our Neuronal Selves, by French cognitive psychologist Stanislas Dehaene. Actually, I read the original French edition, published in 2021, but I don’t have access to the English edition, published in 2023, so the following excerpt is my own translation:
As we age, certain neurons, and especially the large inhibitory neurons that control the activity of their surroundings, become wrapped in a perineuronal net,a rigid lattice that holds them still. This aggregate of proteins and sugar chains, which has some of the same ingredients as cartilage, prevents the nerve cells from changing. Hence they cannot form new connections or even alter existing ones; emprisoned in this net, the neuron loses its plasticity.
From the Simple to the Complex | Comments Closed
Wednesday, 24 July 2024
How Andy Clark’s career path mirrors that of cognitive science over the past 40 years
This week I’m just going to copy and paste a paragraph from a chapter of my book ( to be released in French on October 1, 2024 ) in which I describe the career of Andy Clark, an important philosopher of cognitive science, and draw your particular attention to his latest book, The Experience Machine: How Our Minds Predict and Shape Reality, which he discusses in this stimulating interview.
I will start by just briefly describing the career of Andy Clark, a philosopher of cognitive science whom I like a lot, and his encounter with Karl Friston. Because Clark’s career path, all on its own, sums up the major trends in cognitive science over the past 40 years that I talked to you about at our first meeting. First, in keep with the cognitivist paradigm that prevailed at the time, he studied symbolic artificial intelligence, also known as computationalism. Then he became interested in connectionism— in virtual neural networks, thus more closely approximating the human brain, which can learn by modifying its internal connections. After that, he jumped aboard the train of embodied cognition, thus including the entire body in the equation of our cognitive processes, and even the objects in our environment (the concept of extended cognition, of which is he one of the most ardent proponents). And lastly, he made important contributions to the Karl Friston’s bold ideas about predictive processing, the principle of free energy and active inference—in short,all of the concepts whose broad implications I will now discuss.
From the Simple to the Complex, From Thought to Language | Comments Closed
