The Brain Does Not Light Up

No technology in recent history has played a bigger role in increasing our knowledge of the human mind than functional magnetic resonance imaging (fMRI). For this reason, findings from experiments that use fMRI receive significant media attention. As a scientist who used this technology, I am thrilled by this development.

controlling-the-brain-with-light_1Unfortunately, media reports about this research use language that prevents readers from understanding results from this work accurately. One of the worst offenders in this category is the phrase “lights up,” which neuroscience commentators insist on using to describe fMRI findings. For example, a reporter might say that the amygdala “lights up” when we feel fear or that the prefrontal cortex “lights up” when we make financial decisions.

This phrase gives the impression that brain regions are dark, silent creatures that wait patiently for a person to perceive or think about the right thing so that they may do their job. This mistaken impression not only misrepresents what fMRI does, but it also makes findings from this research difficult to interpret. Consequently, people cannot be appropriately critical of these discoveries.

The Importance of Differences

FMRI allows scientist to study the brain by measuring changes in its blood activity. Oxygenated blood rushes to a brain region after its neurons fire. When fMRI detects this hemodynamic response, scientists infer that the brain regions in which they took place experienced significant neural activity. This is akin to seeing someone in a gym drinking water and inferring that this person was working out.

However, brain regions are more like gym goers who are constantly drinking water, but who drink more after particularly heavy exercise. Blood courses through the arteries of every brain region at all times, but increased levels of oxygenated blood will rush to certain regions after perceiving or thinking about some stimuli more than others.

By understanding the stimuli differences that correlate systematically with changes in oxygenated blood in a brain region, scientists can start to reveal brain function. The phrase “lights up” misses this emphasis on relative, rather than absolute, brain activity. Consequently, fMRI findings cannot be communicated to the public appropriately.

An Example

For example, imagine that a group of scientists has participants in an fMRI study view images of faces in some cases and images of objects in others. These researchers find a brain region that shows higher levels of oxygenated blood after viewing faces instead of objects. In fact, two different groups of scientists discovered such a brain region (Kanwisher, McDermott, & Chun, 1997; McCarthy, Puce, Gore, & Allison, 1997) in the fusiform face area (FFA).

A headline reporting that FFA “lights up” to faces would rob the real finding of meaning. Oxygenated blood always courses through this brain region so the headline would be trivial. What was so important about the discovery of FFA was the fact that this brain region shows more changes in blood activity during the perception of faces than objects.

This result suggested that the way in which the brain perceives the world visually is organized along categories and that faces form one such category. More than a decade of additional research provides additional support for this view (Kanwisher & Dilks, 2013).


In fMRI research, the devil is in the differences: Differences in the stimuli shown to participants are associated with differences in brain activity. Scientists gain insights into the function of a brain region by understanding how stimuli differences correlate with changes in its blood activity.

This important point is lost on neuroscience commentators who write that brain regions “light up.” Though this phrase may help to distill complicated findings into simple headlines, it comes at a significant cost: A public who misunderstands the important and exciting findings that are slowly, but surely, helping us to understand the human mind.

When you read media reports about an fMRI experiment, be skeptical about a brain region that “lights up.” Ask whether you have information about which differences in brain activity were studied in the experiment. Consider what you think these differences might reveal about how the human mind works. Does your interpretation of the results align with the one proposed by the journalist and the scientists?

“Lights up” is by no means the only phrase that misrepresents fMRI research, but it is one of the most pervasive. If you read journalism about this neuroscience with a critical eye that goes beyond brain regions with light switches, then you will have a greater understanding of how these experiments are changing the way in which we understand ourselves.

4 thoughts on “The Brain Does Not Light Up

  1. Pingback: The Brain Does Not Light Up | Cognitive Psychol...

  2. Another great post JM. Do you plan to write future posts about other popular misunderstandings that you reference at the end of the article? I completely agree with this post, and I’d be interested to see what other common misrepresentations you have identified.

  3. Pingback: Fascinación con el cerebro y lo neuro

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