Sunday, September 19, 2010

Brains and birthdays

We hear a whole lot about new brain imaging techniques lately. It seems like imaging studies are constantly revealing new pieces of information about the brain: what part of the brain is responsible for our morality, what happens when you fall in love, and so on. One of the main techniques used in these studies is called functional magnetic resonance imaging (fMRI). Unlike a regular MRI, which takes a static image, fMRI can give us images of a dynamic process: the flow of oxygenated blood in the brain. Presumably, when one region of your brain is activated, the brain cells require more oxygen, so more oxygenated blood flows to that region, and this can be seen and measured using fMRI.

While it may be very interesting to find out what happens to your brain when you fall in love, we have yet to see real clinical benefits from these fancy new brain scans. Brain disorders and diseases, such as depression and Alzheimer’s disease, still cannot be diagnosed using fMRI. One of the reasons for this limitation is that an fMRI scan for a single person really doesn’t tell us much: we can only gain insights from this technique if we look at groups of people, and compare averages. To this day, this problem has really limited the potential of fMRI for diagnosing brain diseases. However, a recent publication in the journal Science suggests that fMRI may soon be clinically relevant.

The researchers were interested in finding an application where a single brain scan could provide information about the individual. They chose to assess the maturity of the brain, and used chronological age as a reference measure. Instead of using regular fMRI, the researchers used an even fancier version, fcMRI (fc stands for “functional connectivity”). This type of imaging measures the spontaneous activity between brain regions. How strongly different brain regions interact with each other is thought to be shaped by all the experiences one accumulates over time, hence the potential to determine maturity from these kinds of measures.

Participants aged seven to 30 years old were asked to undergo a five-minute brain scan. What followed was an extremely complex series of models and algorithms developed by the researchers to establish a “maturation curve”, from which they could then predict the maturity of a given brain based on where its scan fits along the curve.

Ultimately, it was established that yes, a single scan can provide information about the person’s brain: it can predict its maturity level. But couldn’t we already determine brain age just by looking at its shape? For the most part, yes. The reason this article is relevant is because quite a few brain diseases and disorders don’t have a signature shape (unlike tumors, for example, which can sometimes be spotted on a static image). Therefore, having a tool that allows us to assess brain function without having to compare large groups could become very valuable in the diagnosis of some brain disorders (provided we first determine the functional signature of these disorders).

As an interesting side note, the researchers' results suggest that on average, functional brain maturity levels out at about age 22. This obviously represents a physiological maturity level, not a cognitive maturity level, thank goodness.
When I was 22, I used to think I knew everything. How I've "matured" since then!

Reference: Prediction of individual brain maturity using fMRI. Dosenbach N.U.F. et al. Science 329:1358-61 (2010).

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