Another blow for fMRI: Blood flow does not necessarily correspond to neural signalling

Ed Yong reports,

It’s tempting to think that the signal represented the monkey’s shifting attention, with every peak signifying blood flowing to the area during fixation and every trough corresponding to relaxation. But the signal’s timing said otherwise – it showed that blood was starting to flow into the area before the start of each trial period, while the monkey was meant to be relaxing its gaze.

Interpretations of fMRI experiments hinge on the idea that haemodynamic signals can predict the activity of neurons in specific parts of the brain. This new study shows that this is true to an extent. But it also reveals the existence of another group of signals that is just as strong and has absolutely nothing to do with local neurons.

The article relays the findings from a recent paper by Yevgeniy Sirotin and Aniruddha Das from Columbia University on monkeys. After the recent statistical questions about fMRI, this study adds to the growing pile of criticisms. It is important to remember that fMRI still has applications in medicine and brain-computer interfacing, even though it can no longer be soundly considered a one-to-one mapping of the brain.