Suppose you're presented with a totally new type of computer and
challenged to discover how it works without taking it apart.
You're allowed to have the computer do certain tasks, and you're
allowed to use a temperature sensor to determine which
components, circuits, and so on are active at any moment, given
the proposition that activity will be reflected by the generation
of local heat.
A tough challenge, isn't it? Suppose the computer is running a
sophisticated text editor and you tell the program to load some
particular text file, read the text, then substitute "bred" for
"red" wherever "red" appears unattached to any other letters.
Using only the temperature sensor, your job is to figure out how
the hardware and software work together to carry out the search-
and-replace task.
If the computer involves new engineering, it may take you a
hundred years to get to second base in understanding how this
machine works.
Magnetic resonance imaging (MRI) and functional magnetic
resonance imaging (fMRI) are two techniques of considerable
importance in current biomedical research. MRI is essentially a
technique for examining morphology (structure), while fMRI is a
technique for examining activity of brain tissue. Both techniques
involve computerized analysis of data.
In general, the interaction physics in MRI is that between the
magnetic fields and atomic nuclei in brain tissue, with the
imaging tuned to interactions with specific atomic nuclei that in
many cases are artificially introduced into the system to achieve
resolution of various structures. "Sliced" views can be obtained
from any angle, and the resolution is quite high and on the order
of millimeters.
Functional magnetic resonance imaging (fMRI) (functional
brainscanning), a variant of MRI, is based on the fact that
oxyhemoglobin, the oxygen-carrying form of hemoglobin, has a
different magnetic resonance signal than deoxyhemoglobin, the
oxygen-depleted form of hemoglobin. Activated brain areas utilize
more oxygen, which transiently decreases the levels of
oxyhemoglobin and increases the levels of deoxyhemoglobin, and
within seconds the brain microvasculature responds to the local
change by increasing the flow of oxygen-rich blood into the
active area. This local response thus leads to an increase in the
oxyhemoglobin-deoxyhemoglobin ratio, which forms the basis for
the fMRI signal in the fMRI technique. Because of its high
spatial resolution (millimeters) and high temporal resolution
(seconds) compared to other imaging techniques, fMRI is now the
technology of choice for studies of the functional architecture
of the human brain: in other words, it's used to study which
parts of the brain are active during specific activities.
As you might imagine, determining how the human brain works with
fMRI is in the same ball-park of difficulty as determining how
our mystery computer works with only a temperature sensor.
Of course, neuroscientists have more than brainscans to work
with, but at the moment, especially among neuropsychologists who
focus on "phrenics" (on the "mind"), brainscanning is the latest
research fashion, and whether the researchers like it or not, it
gets plenty of media attention.
In today's New York Times, a full page is
devoted to a study linking brainscan results to politics, the
article entitled "This Is Your Brain on Politics". Functional
magnetic resonance imaging (fMRI) was used to scan the brains of
20 registered "swing" voters (they said they were open to
choosing a candidate from either party) while they looked at
still photos of various candidates in the coming 2008
Presidential election. The article in the Times was evidently
written by the researchers themselves.
The authors present eight conclusions:
1. Voters sense both peril and promise in party brands.
2. Emotions about Hillary Clinton are mixed.
3. Hillary Clinton and Rudi Guliani are on opposite sides of the
gender divide.
4. The gender gap may be closing.
5. Mitt Romney shows potential.
6. Fred Thompson evokes more empathy than Rudi Guliani.
7. John Edwards has both promise and a problem.
8. Barack Obama and John McCain have work to do.
I may be an old grouch, but the problem for me is that this sort
of analysis is more entertainment than science, the phrenics
close enough to phrenology to make me uncomfortable. The various
parts of the human brain are always working together, especially
when the brain is confronted with something as complex as
politics, and the idea that increased activity in a particular
part of the brain is de facto evidence for functional dominance
of that part during some activity is in many cases wishful
thinking. It's not that easy, folks. Apparent fMRI activation of
the amygdala (a brain region) while you're looking at a photo of
Mitt Romney does not mean much except that activity in the
amygdala has increased: you may or not actually feel anxious. You
may instead feel some other emotion. And the same is true for
other parts of the brain. The study found that when women looked
at a photo of Hillary Clinton, they had more activity in the
visual cortex than when men looked at her. Do an exercise: write
down all the reasons why there might be more activity in the
visual cortex of women than men in response to a photo of Hillary
Clinton. And consider that the total number of subjects in this
study was 20 people, about the number of people in a small diner
on the road from Dubuque to Des Moines.
We know too little about how the human brain works to jump to
conclusions about the political implications of neurological
activity. I wish the authors of the newspaper article had
bothered to be explicit about the limitations of their study.
Instead. they give us the following: "Our results reveal some
voter impressions on which this election may well turn."
Not so. Definitely not so.