Astrocyte Glial Cells in the Brain

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Quantum dot labeled connected astrocytes. Silva Lab, University of California San Diego

Imagine, if you will, a recipe you know well. Something delicious you’ve never made yourself but have seen your mom make many times. Let’s assume it’s pumpkin pie. The receipe calls for canned pumpkins, heavy cream, eggs, cornstarch, sugar, maybe even a touch of nutmeg. You’ve seen your mom make it more times than you can count. Geez, you could practically make it yourself from memory. But what if in reality, as it turns out, your mom’s pumpkin pie also requires sardines. Almost as much sardines as pumpkin. …


In Pursuit of the Transcendental Reality of Mathematics

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Mathematics is this beautiful and private world of pure thought and pure reason. There is no war, no hunger, no pain. No suffering and no regrets. Only beauty. Beauty in its purest form without blemishes and without the messiness of the physical world. It is a product of thought and reason. It does not have any physical counterpart, and it is not an approximation of anything. It is by its very construction and conception its own self, and does not rely on or need to be apologetic for being represented by a less than perfect bastardization of its true nature. (You can never really draw a circle. …


Physical Constraints Regulate Information Dynamics

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Connected neurons. Silva Lab, University of California San Diego

Everything the human brain is capable of is the product of a complex symphony of interactions between many distinct signaling events and myriad of individual computations. The brain’s ability to learn, connect abstract concepts, adapt, and imagine, are all the result of this vast combinatorial computational space. Even elusive properties such as self-awareness and consciousness presumably owe themselves to it. This computational space is the result of thousands of years of evolution, manifested by the physical and chemical substrate that makes up the brain — its ‘wetware’.

Physically, the brain is a geometric spatial network consisting of about 86 billion neurons and 85 billion non-neuronal cells. There is tremendous variability within these numbers, with many classes and sub-classes of both neurons and non-neuronal cells exhibiting different physiological dynamics and morphological (structural) heterogeneity that contribute to the dynamics. A seemingly uncountable number of signaling events occurring at different spatial and temporal scales interacting and integrating with each other are responsible for the brain’s computational complexity and the functions that emerge. …


Machine Learning meets Neural Engineering

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I’m going to confess something I’ve never told anyone. The inspiration for much of my current research at the intersection between neuroscience, mathematics, and machine learning was inspired by a single beautiful scene in the movie Ex Machina. There is a scene where the movie’s two protagonists Nathan and Caleb are in the lab where Nathan built Ava, a humanoid artificial intelligence (AI), where they share an exchange about how Nathan engineered Ava’s brain. “Structured gel. I had to get away from circuitry. I needed something that could arrange and re-arrange at a molecular level, but keep its form when required. Holding for memories, shifting for thoughts.” Of course, science fiction has a long history of motivating and inspiring what eventually becomes real science. …


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When I tell people that I use mathematics and engineering to study and understand how the brain works, the reaction I get is oftentimes one of confusion. Despite the seemingly head scratching connection between the two, the reality is that we will never be able to understand how the brain works as a system without the use of mathematics and related applied fields of physics and engineering. To understand why, we first need to understand something about how complex the brain is.

The brain is truly a complex system, in the sense that the whole is greater than the sum of its parts. …


A researcher explains the significance of brain organoids

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A human-derived brain organoid. Image courtesy of Alysson Muotri’s lab at the University of California, San Diego

Your brain is not like mine. In fact, your brain is not like anyone else’s. I don’t mean that in some philosophical or abstract way; I mean it literally. The precise wiring of your brain is unique to you. During development, your genes specified a blueprint that resulted in your brain having roughly the same organization as mine. But that genetic blueprint wasn’t designed to specify the precise connection patterns between all the neurons in your brain.

The exact wiring diagram of the networks of cells in your brain is the result of random processes influenced by external and environmental factors and stressors — in other words, the ways in which you interact with the world and the world interacts with you. As a result, how your brain takes in and processes information is also specific to you. You truly are a neurobiologically unique individual. …


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When I was a kid I sometimes imagined that everyone I knew were actually alien beings that would put on human looking masks whenever they interacted with me. Whenever I wasn’t paying attention they would take off their masks and look, well, however it was they looked like in their natural state. It was as if I was at the center of some strange alien experiment that revolved around tricking me about the true nature of reality. My own personal Truman Show long before the movie ever came out. Of course, I never really believed it was real. But it occurred to me that even though I knew it was not true, I had no real empirical or objective way of proving it to myself. If it was true and alien beings really were putting on masks, by the very nature of how I set this up in my head I couldn’t catch them in the act. …


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There’s no sugar coating it. Writing is hard. Writing about science for a lay audience and the general public is really hard. You may have to communicate inherently difficult or abstract concepts, or provide a rationale for the interpretation of complex data. Often times the challenge is where to start. How much do you assume your reader knows coming in? Which begs the question: Whom are you writing for? It is impossible to write about science, engineering, and mathematics without assuming some degree of background knowledge and understanding, but how much and the level of detail of your exposition are always difficult choices to make. You need to communicate ideas clearly, which implies they are clear in your mind first, and then pick from a variety of writing approaches, tools, and methods to articulate what you want to get across. …


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In the first part of this series of three articles we introduced and reviewed how photons are ‘converted’ or transduced into a neurochemical signal, the language of the brain, by photoreceptor neurons in the sensory retina. In the second part we discussed how visual information is processed by the rest of the inner retina and the other parts of the visual system in brain. In this last part we will discuss some of the information theoretic implications of visual information. In other words, how is the information in the visual system actually encoded from a mathematical perspective?

Phototransduction is a predictable stereotyped event. So where is the information

If you recall from the first article in the series, photons are transduced or changed from little packets of energy into a neurochemical signal the brain can understand in photoreceptor neurons in the retina. What this really means is that the energy in the photons are used to break one single chemical double bond in a specific molecule that then triggers a biochemical cascade that eventually leads to physiological changes that get passed on from one neuron to another eventually all the way to the brain. And that is it. That is only thing that photons do. They provide the energy needed to break a chemical bond. And they do the same exact thing every time, billions of times over. Everything that you see and visually perceive, the entire richness of the visual world around you, all of the raw information that enters your eyes that your brain has to work with, begins as a highly repetitive and boring stereotyped chemical event. Realize that there is very little information (in fact, exactly one bit of information) in any one given photon-retinal molecular interaction. There is obviously a lot of valuable information received by the parts of the brain that process visual signals from the retina. But that information is all in the spatial and temporal patterns or distributions of these photoiosmerization events, with only a tiny bit contributed by any one given event itself. It is truly an incredible process. …


In the first part of this series of three articles we reviewed in some detail how photons are ‘converted’ or transduced into a neurochemical signal, the language of the brain, by photoreceptor neurons in the sensory retina. In this part we briefly discuss how visual information is processed by the rest of the retina and other parts of the brain. The last article in this series we will discuss some of the information theoretic implications of visual information. In other words, how is the information in the visual system actually encoded from a mathematical perspective. …

About

Gabriel A. Silva

Prof. of Bioengineering and Neurosciences |Director, Center for Engineered Natural Intelligence |Ass. Director, Kavli Institute for Brain and Mind, UC San Diego

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