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Are studies of brain activity all wrong?

What we think we know about how the brain works could be fundamentally wrong according to researchers at Duke University, who claim that the measurement these studies are based on isn't accurate.

For the past several decades, scientists have relied on functional magnetic resonance imaging (fMRI) to assess which brain structures are being used when we complete a task. For example, studies where adults were asked to view emotional pictures or recall a list of words or numbers while undergoing an fMRI scan were thought to accurately reflect which parts of the brain were active while they performed the task.

The assumption underlying this research was that what occurs in a person's brain would be relatively stable. Results of the Duke study suggest otherwise. They found that people's brains did not perform in similar or predictable ways from one time to the next.

This variation most likely occurs because fMRIs measure blood flow to the regions of the brain that are being used rather than the activity of the brain cells themselves. The studies in question have relied on the overarching assumption that this blood flow is a proxy for brain activity. That belief appears to be wrong.

The researchers discovered this while reexamining 56 peer-reviewed, published papers that included 90 fMRI experiments, in addition to “test/retest” fMRIs, where 65 subjects performed the same tasks months apart.

Their review showed none of the seven measures of brain function had consistent readings from one time to the next. This calls into the question the results of hundreds of studies, as well as our assumptions about how the brain works, and may very well turn the field of functional neuroscience on its ear temporarily as neuroscientists move to create new and more accurate ways to measure brain activity in the future.

Read the original study here.

Elliott Knodt et al 2020 fMRI reliabilit
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