Ferromagnetism and the Brain

What does the fact that a piece of iron loses its magnetism above the Curie temperature (1043 F) have to do with the brain? The electrical activity of neurons does create extremely weak magnetic fields and the activity can be affected by extremely strong magnets. The latter effect is sometimes used by experimenters to modify ongoing brain activity, but the reason why we study the ferromagnetic phase transition is because it's a simple example of self-organization. The human mind is an almost (but not quite!) magical outcome of the interaction of billions of neurons, which is a rather poorly understood example of a phase transition (loss or gain of self-organization)  - neural matter leading to mind rather than watery matter transforming from liquid to solid as it freezes). Even freezing is quite a complicated process so we first looked at an even "easier" example: the ferromagnetic phase transition.

<script type='text/javascript' src='http://demonstrations.wolfram.com/javascript/embed.js' ></script><script type='text/javascript'>var demoObj = new DEMOEMBED(); demoObj.run('The2DIsingModelMonteCarloSimulationUsingTheMetropolisAlgorit', '', '459', '648');</script><div id='DEMO_The2DIsingModelMonteCarloSimulationUsingTheMetropolisAlgorit'><a class='demonstrationHyperlink' href='http://demonstrations.wolfram.com/The2DIsingModelMonteCarloSimulationUsingTheMetropolisAlgorit/' target='_blank'>The 2D Ising Model Monte Carlo Simulation Using the Metropolis Algorithm</a> from the <a class='demonstrationHyperlink' href='http://demonstrations.wolfram.com/' target='_blank'>Wolfram Demonstrations Project</a> by Darya Aleinikava</div><br />

More to follow, including links to videos.

BIO 338; “L’esprit de l’escalier”

me lecturing (on hummingbirds not the brain).

I teach an advanced undergrad class in neuroscience at Stony Brook University (BIO 338 “From Synapse to Circuit: Self-Organization of the Brain” , and I’ll be using this blog to provide a running commentary on the course, explain background, and hilight interesting student questions and my answers to those questions. Often when teaching I find I come up with better ways to explain things after class rather than during class itself (when one is under time pressure), and this way I can share my thoughts with students. I don't expect students to learn the additional material I present here, though if I present the same idea in both the class and the blog, you should learn it. However, when you write your essays, you might find the relevant blog posts helpful.

So let’s start with a prospective student’s interesting question: “How exactly can this course quantify the mind?”. Here is my initial answer:

“The course does not aim to “quantify the mind” but to try to understand it (i.e. understand understanding itself). In science one does this by constructing “models” i.e. mental representations of how aspects of the world operate. Since these models try to link high-level concepts like “memory”, “thinking”, “understanding” etc to low-level processes such as the firing of millions of neurons, they must be quantitative – one cannot easily reason about the behavior of highly nonlinear complex systems (eg the weather) without quantitative methods (eg computer simulation, math etc). Of course one cannot yet completely understand the brain, or the weather/climate, but we are making progress and the course will highlight some aspects of that progress. Of course a clinical doctor does not need to understand how the brain works, any more than you need to understand how weather predictions are generated. But a neuroscientist does.”

This is why we start with the example of ferromagnetism, which is a simple model of a complex system (a collection of interacting iron atoms). Using semi-quantitative tools we can actually see why spontaneous magnetism (a large-scale result of small-scale behavior) emerges.

The french in my title refers to the fact that one’s best joke or retort often arises as one is leaving the party (i.e. going down the stairs, from the “piano nobile” or principal floor of a mansion).