On bumpology: what neuroscience knows

Adam Gopnik has a review in the New Yorker of several neuroscience-themed books. Or perhaps I should say, he has a review of several books that use neuroscience-related words. As he points out, one of the problems with neuroscience happens to be the people who love the sound of neuroscience:

A core objection is that neuroscientific “explanations” of behavior often simply re-state what’s already obvious. Neuro-enthusiasts are always declaring that an MRI of the brain in action demonstrates that some mental state is not just happening but is really, truly, is-so happening. We’ll be informed, say, that when a teen-age boy leafs through the Sports Illustrated swimsuit issue areas in his brain associated with sexual desire light up. Yet asserting that an emotion is really real because you can somehow see it happening in the brain adds nothing to our understanding. Any thought, from Kiss the baby! to Kill the Jews!, must havesome route around the brain. If you couldn’t locate the emotion, or watch it light up in your brain, you’d still be feeling it. Just because you can’t see it doesn’t mean you don’t have it. Satel and Lilienfeld like the term “neuroredundancy” to “denote things we already knew without brain scanning,” mockingly citing a researcher who insists that “brain imaging tells us that post-traumatic stress disorder (PTSD) is a ‘real disorder.’ ” The brain scan, like the word “wired,” adds a false gloss of scientific certainty to what we already thought. As with the old invocation of “culture,” it’s intended simply as an intensifier of the obvious.

It’s always perplexing that you can take a study that shows something “lights up” an area of the brain and the press will ooooh and aaaah over it. The problem is not that it’s bad science – it often isn’t – the problem is that it doesn’t tell the lay-person anything. At all. To a scientist, these studies can be fascinating springboards to further research, or clarity for previous technical research. Take, for instance, two fantastic studies that used electrode recordings to localize two types of uncertainty to the pulvinar and the septum. As a scientist, the results were nontrivial and important for our understanding of how uncertainty is represented and used in the brain. To a non-specialist the takeaway message is: uncertainty exists in two strangely-named areas in the brain…? It’s a prime reason why, despite being important, I don’t highlight those kinds of papers in this blog.

But then Gopnik undermines his point:

She discusses whether the hormone testosterone makes men angry. The answer even to that off-on question is anything but straightforward. Testosterone counts for a lot in making men mad, but so does the “stress” hormone cortisol, along with the “neuromodulator” serotonin, which affects whether the aggression is impulsive or premeditated, and the balance between all these things is affected by “other hormones, other neuromodulators, age and environment.”

Yes, the role of neuromodulators is unfortunately complicated (I’ll let out a personal sigh, here). Yet this example of a seemingly convoluted mechanism is a fantastic example of something we actually know a fair bit about. Serotonin levels actually have a causative role in the rate of aggression – animals that are given a serotonin inhibitor will begin exhibiting less aggression. You can actually map out some of this circuitry in crustaceans to find out exactly how serotonin is acting! In mammals, serotonin seems to have two ways of affecting aggressive behavior. Serotonin release in the striatum will modify dopamine activity, a proxy for the rewarding value of an [aggressive?] action. In other words, serotonin makes being aggressive seem like a less attractive option. Simultaneously, serotonin in the prefrontal cortex inhibits the transmission of signals coming from the amygdala – or, the top-down (self-control) area begins regulating the aggressive signal coming from another area. Complicated? Yes, it can be. But why would you expect the brain to be so simple?

More importantly, there are areas where neuroscience has provided fantastic explanations for how we perceive the physical world. The greatest success in my mind is in the realm of optical illusions. We’ve known about these illusions for a long time but it is only recently that we can give firm physical and neurological explanations for why they occur.  There are many examples out there.

The problem is that once something is explained it is no longer interesting. I think Gopnik is hoping for a concise answer to hard problems – but we’re not there yet.