[CG] The immensity of the human brain (was The central executive

Neil, Thanks for the reference. Very short summary: a representation of one cubic millimeter of human brain tissue takes1.4 petabytes. And that is just one millionth of the total volume of the brain. However, each neuron is far more complex than the artificial NNs, which are just simple switches with no internal structure. Each neuron (in humans and other beasties) has the ability to store a very large amount of information, say X. But the size of X is still unknown. To get an estimate of how much computer storage would be necessary to simulate a human brain, multiply one million times 1.4 petabytes times the number of neurons (57 thousand) times the number of synapses (150 million) times some large number X. However, it might not be necessary to simulate every feature of every neuron. It might be possible to recreate the function with some smaller amount of hardware. So you might divide that huge number by 10 or even by a million or even by a billion. But you are still left with a very, very, very big number. Conclusion: Simulating the full power of the human brain is not possible with any computer hardware & software available today or the foreseeable future. And nobody knows how many more years of research and development of hardware and software would be required to simulate the brain of a rat, let alone the brain of a human. Some people claim that a simulation of the brain is not necessary. It might be possible to simulate the function of the brain by some other method. Yes, that might be possible. But just note the neuroscientists' favorite nematode, C. elegans. It has a total of just over 300 neurons. They have been trying to simulate its abilities for quite a few decades without success. And 300 is trivial compared to that huge number above. See below for some excerpts from the article that Neil cited. John _____________________ One cubic millimetre of brain mapped in spectacular detail https://www.nature.com/articles/d41586-024-01387-9 Researchers have mapped a tiny piece of the human brain in astonishing detail. The resulting cell atlas, which was described today in Science and is available online, reveals new patterns of connections between neurons, as well as cells that wrap around themselves to form knots, and pairs of neurons that are almost mirror images of each other. The 3D map covers a volume of about one cubic millimetre, one-millionth of a whole brain, and contains roughly 57,000 cells and 150 million synapses — the connections between neurons. It incorporates a colossal 1.4 petabytes of data. “It’s a little bit humbling,” says Viren Jain, a neuroscientist at Google in Mountain View, California, and a co-author of the paper. “How are we ever going to really come to terms with all this complexity?” Jain’s team then built artificial-intelligence models that were able to stitch the microscope images together to reconstruct the whole sample in 3D. “I remember this moment, going into the map and looking at one individual synapse from this woman’s brain, and then zooming out into these other millions of pixels,” says Jain. “It felt sort of spiritual.” When examining the model in detail, the researchers discovered unconventional neurons, including some that made up to 50 connections with each other. “In general, you would find a couple of connections at most between two neurons,” says Jain. Elsewhere, the model showed neurons with tendrils that formed knots around themselves. “Nobody had seen anything like this before,” Jain adds. “This paper is really the tour de force creation of a human cortex data set,” says Hongkui Zeng, director of the Allen Institute for Brain Science in Seattle. The vast amount of data that has been made freely accessible will “allow the community to look deeper into the micro-circuitry in the human cortex”, she adds. Gaining a deeper understanding of how the cortex works could offer clues about how to treat some psychiatric and neurodegenerative diseases. “This map provides unprecedented details that can unveil new rules of neural connections and help to decipher the inner working of the human brain,” says Yongsoo Kim, a neuroscientist at Pennsylvania State University in Hershey. ---------------------------------------- From: "Neil McNaughton" <neilmcn(a)oilit.com> See recent Science/Nature announcement of a cubic mm of a brain imaged https://www.nature.com/articles/d41586-024-01387-9