Neuromythology — The New Phrenology

There’s a commonly held idea that certain parts of the brain serve particular functions, partially true. During stress and anxiety the amygdala, for instance, lights up. What’s not always understood is that the amygdala lights up under other conditions as well. An excellent article at Scientific American “The Brain is Not Modular” outlines some of these ideas. Here’s a quote from the article:

As cognitive neuroscientists who use the same brain imaging technology, we know that it is not possible to definitively determine whether a person is anxious or feeling connected simply by looking at activity in a particular brain region. This is so because brain regions are typically en­gaged by many mental states, and thus a one-to-one mapping between a brain region and a mental state is not possible. For example, the amygdala is activated by arousal and positive emotions as well, so the key to interpreting such scans is careful experimental design that allows comparison between brain states.

Additional skepticism arises from knowing that fMRI measures blood-flow change, not neuronal activity, that the colors are artificially added in order to see the blood-flow differences and that those images are not any one person’s brain but are instead a statistical compilation of many subjects’ brains in the experiment. “Some of the claims made by neuroscientists sound like astrology,” Poldrack told me in an interview. “It’s not the science itself that is the problem. It’s taking a little bit of science and going way beyond it.” For example, there is the problem of reversing the causal inference, “where people see some activity in a brain area and then conclude that this part of the brain is where X happens. We can show that if I put you into a state of fear, your amygdala lights up, but that doesn’t mean that every time your amygdala lights up you are experiencing fear. Every brain area lights up under lots of different states. We just don’t have the data to tell us how selectively active an area is.”

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