Functional magnetic resonance imaging (fMRI), used to map brain activity, gives a signal when the levels of oxygenated blood increase. The signal is often preceded by a darkening, thought to indicate early oxygen absorption by the brain owing to local neural activity.
But a study by Aniruddha Das and his colleagues at Columbia University in New York casts doubt on this. They used intrinsic signal optical imaging, a technique similar to fMRI, to measure changes in blood volume and blood oxygenation in the brains of two macaques while they performed a visual task.
The researchers found that during the initial darkening, blood-oxygen levels changed little, but blood volume increased markedly. The team suggests that blood-volume change is a better signal to use in brain imaging because it seems to be more closely linked to neural activity, occurring even before changes in blood oxygenation.
Rights and permissions
About this article
Cite this article
Neuroscience: Brain signal source. Nature 461, 1177 (2009). https://doi.org/10.1038/4611177b
Published:
Issue Date:
DOI: https://doi.org/10.1038/4611177b