CONTRARY to popular belief, a rush of blood to a certain brain region is not always linked to neural activity there, a finding that may guide future brain scan experiments.
Functional MRI scans measure blood flow in the brain. Neuroscientists interpret this as a sign that neurons are firing, usually as someone performs a task or experiences an emotion. This enables them to link the emotion to the brain region where there was blood flow.
Now, from Columbia University in New York and colleagues have shown that blood flow can occur without accompanying neural activity. Das used separate techniques to measure blood flow and neural activity in the visual cortex of two macaques trained to carry out a visual task.
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Sitting in darkness except for a light that switched on at regular intervals, the monkeys were trained to look away if it was red, and fix their gaze on the light if it shone green. When the timing of the pauses between the light flashes changed, blood flow still increased when the macaque expected a flash, but there was no subsequent increase in electrical activity from firing neurons (Nature, ). Das suspects that the brain sent the rush of blood in anticipation of the neurons鈥� firing.
Christian Keysers from the BCN Neuroimaging Centre in Groningen, the Netherlands, does not believe the result is relevant to the design of previous fMRI experiments and so is unlikely to have an impact on their results. But Das says care needs to be taken in future to ensure that this misinterpretation does not lead to errors.
