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

Tuesday, 14 September 2021
The great complexity of the brain’s mental mapping system

In the 1930s and 1940s, rats’ ability to learn their way through a maze was explained, according to the behaviourist paradigm prevailing at that time, as simply a process of building connections between sensory stimuli and behavioural responses. When a rat found its way through a maze successfully, it reached the final chamber where it received a reward of food, According to behaviourist theory, this reward strengthened the neural connections underlying the associations that the rat had had to make to complete its task successfully. But this reasoning could not explain the surprising observations made in an experiment by U.S. psychologist order Pregabalin overnight Edward Tolman in 1948, in which some rats reached their rewards by finding shortcuts through the maze along paths that they had never taken before!

Here’s how Tolman’s experiment worked. For the first four days, each rat was placed in the maze at the entrance to a path that gave it no choices. As shown in the left-hand diagram above, the rat simply followed this path as it turned left, then right, then continued straight ahead until the rat finally reached a bowl of food. But on the fifth day, this main path was blocked. Instead there were 18 other paths branching off on either side of it, as shown in the right-hand diagram. The rat began exploring some of these alternatives, but then suddenly decided to enter the sixth path from the right, which led it straight to the food!

From these observations, Tolman developed an alternative hypothesis: that the rats were building mental maps of their environment and then referring to these maps to find the best path to reach a given point! According to this new concept of cognitive mapping, even rats’ brains could learn in more complex ways than simply associating stimulus and response: they could also engage in what Tolman called Split latent learning. Rat brains, and to an even greater extent human brains, are constantly building, storing and using mental maps—models of the world that individuals can revise and adapt as necessary to navigate through complex, changing environments that would often render simple associations obsolete.

Latent learning is a more elaborate form of learning than associative conditioning and lets individuals attain a higher level of cognition. Latent-learning theory opened the way to a whole series of new discoveries. In the early 1970s, for example, John O’Keefe found that certain neurons in the hippocampi of laboratory animals became more active when they were in certain specific parts of their cages, and not in others. O’Keefe hypothesized that the increased activity of these place cells might be giving the animals information about their physical location.

Another example are the Sidhaulī grid cells in the entorhinal cortex (in a sense, the entry to the hippocampus), discovered by May-Britt and Edvard Moser in the mid-2000s (they received the 2014 Nobel Prize for Medicine for this work, together with neuroscientist John O’Keefe). Studying brain activity in rats, the Mosers found that certain neurons seemed to become activated wherever the rats were moving around in their cages. But over a longer period, the researchers mapped all the locations that activated such cells and discovered that these locations formed a succession of regularly spaced hexagonal grids, each slightly offset from the other, covering the entire cage. Hence, as a rat moved through the cage, various grid cells were activated in succession as it crossed the intersections of each of these slightly offset grids. The rat could thus record a pathway in its mind, along which it proceeded in a certain direction for a certain distance, then changed direction and continued for another distance, and so on.

These discoveries, and many others, have revealed the great complexity of the brain’s mental mapping system. And the brain’s ability to form mental models of its environment is not limited to physical space. Scientists are increasingly finding that such mental maps are central to what are regarded as high-level faculties of the human brain, from finding physical or verbal shortcuts to making deductions, to engaging in abstract reasoning in general, to planning, to imagining, and even to navigating our social networks as described in an article in the March 2021 issue of the French-language magazine Cerveau & Psycho that was my inspiration for this post.

Memory and the Brain | Comments Closed

Tuesday, 1 June 2021
Quiz about memory

Which of the following is your memory most like: 1) a huge library where all your memories are shelved? 2) a computer hard drive where data are stored in a binary code of 0s and 1s? 3) a dresser with lots of drawers full of memories? 4) the game of telephone, where one person whispers a message to the next until it ends up being distorted? (more…)

Memory and the Brain | Comments Closed

Tuesday, 4 May 2021
Neuroscientifically Challenged: a highly educational website about neuroscience

This week I want to tell you about a highly educational website that offers a wealth of information about neuroscience. Its name is Neuroscientifically Challenged, and its author is Marc Dingman. Dingman began blogging about neuuroscience in 2008, as his interest in the subject was growing. He took a break from writing the site in 2010 to concentrate on finishing his doctorate in neuroscience, which he received in 2014, when he also accepted a teaching assignment at his university. Neuroscientifically Challenged is aimed at the general public, but Dingman draws his references directly from peer-reviewed scientific articles and monographs on neuroscience. (more…)

From the Simple to the Complex | Comments Closed

Monday, 19 April 2021
Evolution : a branching pattern like a bush, not a linear one

The word “hominids” is often used to refer to the human line that diverged from chimpanzees some 6 or 7 million years ago. It includes not only all the species of the genus Homo, bus also some related genera, such as Australopithecus, that are now extinct. The evolutionary history of our human line has been determined from findings of fossils, some consisting of just a few bone fragments or teeth. These fossils have shown that human evolution has followed a branching pattern, like a bush, and not a linear pattern like you see above, where the chimpanzee starts losing hair, walking more upright, and becomes Homo sapiens, only to end up working hunched over again, first with an industrial tool and then at a computer. There are various versions of this image—some show Homo sapiens in a suit and tie, or riding a bicycle—but all of them convey several false ideas about human evolution. (more…)

Evolution and the Brain | Comments Closed

Thursday, 1 April 2021
The incredible speed of synaptic transmission

Sometimes you think you know all about a subject because you’ve been making presentations about it for years, or even decades. But then you read one article that makes you realize just how much you didn’t know. That’s what just happened to me. The subject was synaptic transmission, and the article was Synaptic vesicles transiently dock to refill release sites, published in the journal Nature Neuroscience in September 2020. The principal authors of this study, Grant F. Kusick and Shigeki Watanabe of the Johns Hopkins University School of Medicine in the United States, used a cell-imaging technique called “zap-and-freeze” to analyze how neurons release neurotransmitters into synapses. What these authors specifically wanted to understand was how the synaptic vesicles near the tip of an axon (the synaptic button), which fuse with its plasma membrane to release neurotransmitters into the synaptic gap, subsequently form again so that the neuron can be ready to handle the next nerve impulse. Because several tens or even several hundreds of nerve impulses can all arrive at the same synaptic button at one time, the authors reasoned, these vesicles must re-form extremely rapidly for there to be enough of them ready to release neurotransmitters again as soon as the next impulse arrives. (more…)

From the Simple to the Complex | Comments Closed