The Scicurious Brain

The Scicurious Brain

The Good, Bad, and Weird in Physiology and Neuroscience

Does Neuroscience need a Newton?


This past weekend, I read an interesting piece in the New Yorker. It's another one of the current rash of pieces that are warning us (rightly!) to beware of neuro-hype. It references another recent piece in the New York Times, which referenced those fighting back against things like "How Creativity Works" (correct answer: it's very complicated and we don't know), and the ever-present fMRI studies hyped in the news (I've been guilty of a few of those, though I try very hard to be skeptical). Both pieces referenced the excellent Neuroskeptic and Neurocritic (though sadly, the NYT didn't give them the links they definitely deserve). And both pieces warned that neuroscience is more, and better than, the gee-whiz of "This is your brain on poker".

I particularly liked the New Yorker piece, for making clear the incredible complexity of the human brain.

The brain, though, rarely works that way. Most of the interesting things that the brain does involve many different pieces of tissue working together. Saying that emotion is in the amygdala, or that decision-making is the prefrontal cortex, is at best a shorthand, and a misleading one at that. Different emotions, for example, rely on different combinations of neural substrates. The act of comprehending a sentence likely involves Broca’s area (the language-related spot on the left side of the brain that they may have told you about in college), but it also draws on the parts of the brain in the temporal lobe that analyze acoustic signals, and part of sensorimotor cortex and the basal ganglia become active as well. (In congenitally blind people, some of the visual cortex also plays a role.) It’s not one spot, it’s many, some of which may be less active but still vital, and what really matters is how vast networks of neural tissue work together.

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I love this, and I'm making a promise that I will put something like this, to make it REALLY clear, into every future fMRI piece I write about (and readers, CATCH ME and yell at me if I don't!). We neuroscientists often neglect to mention that sort of thing. We know, intellectually, that when you see a study showing "activity" in the striatum with a drug-associated cue in an addict, they are filtering out the other activity. The activity in the occipital cortex from seeing drug-associated cues. The sensory activity filtering in from the sounds of the machine and the touch of the pad they are lying on. The highly integrative activity at the level of the thalamus, corpus callosum, and higher areas to process all the sensory information. And the activity at this constantly going on at "lower" levels like the pons, medulla, and others, to keep your hear beating, your lungs breathing. We know all this intellectually, and it's takes a long time to say, so we just...leave it out and focus on the significant findings, just like the authors of the paper usually do. It's not a bad thing, as long as you keep it in mind. But most readers are not scientists and don't know that to say "so and so had higher striatal activity when focusing on a crack pipe" is a simplified view of what's going on.

So I really enjoyed these pieces, and I am very pleased that there are lots of neuro-critics and -skeptics out there to call out the hype (even when they call out me, cause I usually deserve it). I'm amazed that anyone would want to just give up on neuroscience because of some sloppy coverage of sloppy studies. We know we can do better coverage, and better studies. But I did find it rather ironic that the New Yorker piece emphasized the gaps in neuroscience knowledge thus:

Scientists are also still struggling to construct theories about how arrays of individual neurons relate [to] complex behaviors, even in principle. Neuroscience has yet find its Newton, let alone its Einstein.

From a warning about over-simplifying, and a reminder of complexity, to bemoaning the lack of a neuroscientific "Einstein". I'm sure what the author really meant was in regard to say, someone "neuroscience Einstein" figuring out how all networks of individual neurons produce all corresponding behaviors, but...even this doesn't really make sense. To seek a neuroscience Newton (alliteration sounds better), is to seek after that same oversimplifying that the author is even now protesting against. I don't think the author meant that we should seek a neuroscience Newton, instead he was commenting on how neuroscience does not yet have a lot of the answers, but should we? Does neuroscience need a Newton?

I personally think such a concept is impossible. Physics, math, these are simple, elegant fields. When it comes down to the very basics in physics and math, particles, if they behave in one way under certain conditions, will always behave that way. A mathematical formula that works once will always work again. At the basis of physics and math, there are unifying ideas and theories that will persist. There are basic principles. But neuroscience is not so elegant. There are basic principles, of course, but they cannot be scaled up. A neurotransmitter may always act on one type of receptor, but how much neurotransmitter is there? How many receptors? What neurons are the receptors on? How many? What types of neurons? Where do they go? Where do the neurons that those neurons contact go? Who do they contact before they get there? Have the receptors themselves been changed or desensitized or understimulated? Change one or a few of these variables, and it's simple. But change all of them. Every single time. For every single connection.

If there was a neuroscience Newton, they existed back when we were first discovering the building blocks. Ramón y Cajal, who first described the neuron as the fundamental unit of the nervous system. Ferrier, who showed that parts of the brain correlated with motor activity. There are many others. But even these are not really neuroscience Newtons. They are not because as we gain more and more knowledge of the brain, we are able to see: there is no unifying theory of the brain. I do not think that we will ever be able to predict an overall production of behavior from a random network of neurons. Yes, we will be able to show what particular networks of neurons do. We will be able to specify (someday, hopefully soon!), how particular networks interact, how they change in response to stimuli, and how they produce behaviors. We will be able to show (and are able to show already) how modification of DNA via epigenetic mechanisms can change the "behavior" of a neuron. We are able to show how certain receptor modifications can change behaviors, can change circuitry. And we can use this ever-growing knowledge base of design new treatments, to apply new drugs or old drugs to new problems.

And in the end, does neuroscience need its Newton? I really don't think it does. Instead of one Newton, standing on the shoulders of giants, neuroscience has thousands (over 30,000 attend the society for neuroscience meeting each year alone) of people, each solving their own part of the puzzle. Each figuring out, under certain sets of conditions, what is and is not true, what is and is not changed. If neuroscientific discoveries should not be simplified in their description, then neither should neuroscience as a discipline. Our field is complex, and many thousands, or millions, of little truths will have to come together before we come to a complete picture of the brain. And for those millions of little truths, you will need a million little scientists.

The views expressed are those of the author and are not necessarily those of Scientific American.

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