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, 11 February 2021
Revisiting an optical illusion in terms of predictive processing

I recently came across a little experiment that I posted years ago on this website to show how the blind spot in each of your eyes works. The blind spot is a part of the retina where there are no photoreceptors, because it is where the axons of the retina’s ganglion cells converge and exit the eye, forming the optical nerve. As a result, there’s a corresponding area in your field of vision that doesn’t register on the retina. Hence, in theory, you shouldn’t see anything there. But in reality, you don’t see any such blank spot in your field of vision.

To find out why not, let’s revisit this optical illusion from the standpoint of predictive-processing theory, which has become more and more accepted in cognitive science over the past 10 years or so. In the traditional view, the brain passively waits to receive inputs, then processes them and ultimately produces outputs, as if it were nothing more than a biologically based computer. In contrast, according to predictive-processing theory, the brain is a proactive organ that is constantly making predictions about its environment and what may be about to happen there, so as to operate within it more effectively.

According to predictive-processing theory, the reason that you don’t notice your blind spot is that your brain makes you blind, so to speak, to the blindness in that part of your field of vision. It does so by filling this area in with the visual information that is most likely to occur there, according to the experience of the world stored in your memory.

The two graphics above give you two ways of experiencing your blind spot.

For the top graphic, close your right eye, look at the + sign with your left eye, then move your head toward or away from the screen slowly while continuing to watch the + sign. The big black dot will disappear as it passes through the blind spot of the retina of your left eye, because your brain projects the surrounding white background onto the corresponding spot in your field of vision.

For the bottom graphic, do the same thing. This time, when the image is at the right distance from your eye, the two lines will look like one solid line. This seems like pure magic, until you apply the theory of predictive processing to explain it: the brain predicts what is most likely to appear in the space between the two lines—a continuation of them—and inserts it there!

You can readily imagine the evolutionary advantages of your brain’s operating in this way. Most of the signals that it receives from the outside world involve a certain degree of ambiguity. If your brain couldn’t project its predictions about the world based on your past experiences, you might, for example, have to wait until the catlike form jumped out of the high grass on the trail ahead of you before you recognized it as a tiger. By then it would probably be too late to run. If your humanoid ancestors’ brains had worked like that, you might not be around here now to worry about it.

The Senses | Comments Closed


Friday, 4 October 2019
Karl Friston: toward a grand unifying theory of life and cognition?

This week I’d like to tell you about a fascinating piece of reporting by journalist Shaun Raviv, in the November 13, 2018 issue of Wired magazine. It’s about one of the most important figures in the cognitive sciences today: Karl Friston. I call Raviv’s piece reporting rather than an interview because he spent more than a week in London in the summer of 2018 researching it. Its title, “The Genius Neuroscientist Who Might Hold the Key to True AI”, might seem sensationalistic, since we all know what a buzzword artificial intelligence has become. But in fact, this title understates the case. As Raviv puts it, “Friston believes he has identified nothing less than the organizing principle of all life, and all intelligence as well.”

What Friston offers is the kind of (very) grand unifying theory that doesn’t come along in science every day. But who is this guy with such big ideas? (more…)

From the Simple to the Complex | No comments


Tuesday, 9 January 2018
The Baseball Batter’s Predictive Brain

For some years now, cognitive scientists have increasingly come to regard the human brain as a machine for making predictions. In other words, these scientists think that our brains spend most of their time trying to figure out what is going to happen next so that they can take action accordingly. The great adaptive value of such a process is immediately obvious.

The theoretical framework underlying this view of things is extensive and fairly new, although it has roots in 18th-century philosophy. Some authors even describe it as a paradigm shift, the same term that has been applied in turn to the cognitivist, connectionist and embodied dynamic approaches over the past half-century. (more…)

Body Movement and the Brain | No comments


Thursday, 26 October 2017
The Brain, The Body and the Environment: We Need All Three To Make Thinking Possible

The third and final session of my course at UPop Montréal started by asking whether our brains really process our most abstract concepts in the way proposed by cognitivist theory: that is, as arbitrary symbols that have nothing to do with the sensory modalities by which these “inputs” are entered. But as early as the 1960s, experiments with the mental rotation of objects seemed to suggest that, on the contrary, when we perform “high-level” mental manipulations of this kind, we employ the sensory regions of our brain to do so. (more…)

Body Movement and the Brain | No comments