Thursday, December 31, 2009

Behavioral fMRI Has No Clothes?

Jonah Lehrer in Wired on Dec 21 tells which brain regions activate in fMRI when physics and non-physics majors watch a falling ball:
[U]ndergraduates... watch a couple of short videos of two different-size balls falling... Galileo’s metal balls all landed at the exact same time — a refutation of Aristotle, who claimed that heavier objects fell faster. While the students were watching the footage, Dunbar asked them to select the more accurate representation of gravity... [U]ndergraduates without a physics background disagreed with Galileo.... [I]n an fMRI machine... showing non-physics majors the correct video triggered a particular pattern of brain activation... to the anterior cingulate cortex.... With physics majors... their education enabled them to see the error, and for them it was the inaccurate video that triggered the ACC...

When physics students saw the Aristotelian video with the aberrant balls, their DLPFCs kicked into gear and they quickly deleted the image from their consciousness.... However, when it comes to noticing anomalies, an efficient prefrontal cortex can actually be a serious liability. The DLPFC is constantly censoring the world, erasing facts from our experience. If the ACC is the “Oh shit!” circuit, the DLPFC is the Delete key. When the ACC and DLPFC “turn on together, people aren’t just noticing that something doesn’t look right,” Dunbar says. “They’re also inhibiting that information.” The lesson is that not all data is created equal in our mind’s eye: When it comes to interpreting our experiments, we see what we want to see and disregard the rest.
In my interview with Colin Marshall on Oct 23 I explained why exactly this doesn't make sense to me:
I have read about some research on human subjects making decisions and undergoing fMRI, but it doesn't make sense to me. Why does it matter that the PFC is lighting up but not the ACC in some given task? Surely it matters to some computational neuroscientist trying to falsify theories, but I can't grok the lay fascination with brain regions.
The experiment is fairly interesting, although it does support what we'd expect a priori, and some numerical group averages would be nice. But I still don't see what the fMRI data adds to it. Yes it's possible that the ACC activating at the same time as the DLPFC can correlate with specific behavioral outcomes, but how does this change our understanding of how people interpret data? It is well known that certain brain regions will activate consistently in certain tasks, and there is little reason that detecting errors in this ball watching paradigm should differ greatly from detecting errors in other paradigms.

Lehrer's article is high quality: so far it has been retweeted 860 times, and it was even discussed on OB, currently the best blog on the internet. But to me the fMRI stuff just seems like black box fluff. Why does it matter to Wired readers whether the brain activation occurs in Brodmann areas 46 and 24 as opposed to any others?

Addendum: See Bob's useful ideas in the comment section, causing me to see how some lay people could find this stuff interesting. I'm leaving the post as is, but with less confidence.