Research Suggests fMRI May Not Map Neuronal Circuitry Precisely

Research results published ahead of print, in the May 25, 2016, online issue of Nature, suggest that discrepancies between vascular and neural responses could point towards limits in the use of functional MR Imaging (fMRI) for precise imaging of neural networks in the brain.

The researchers found that increases in blood flow were not precisely "tuned" to local neural activity during sensory stimulation. Until now vascular and local neural responses were thought to be tightly coupled and scientists using fMRI and other brain-imaging techniques depended on the assumption that vascular changes were directly reflected in a proportional change in local neural activity.


The researchers from the Medical University of South Carolina (MUSC; Charleston, SC, USA) concluded there was not a tight correlation between local neural activity and blood flow, and therefore fMRI and similar techniques could reveal information about the general functioning of an area in the brain, but cannot provide precise maps of neuronal circuits.

Prakash Kara, PhD senior author of the article, and associate professor at MUSC, said, "Because there isn't enough blood to send everywhere in the brain at the same time with the optimal levels of oxygen and glucose needed to support neural activity, it is widely accepted that the brain has a built-in auto-regulatory mechanism for increasing blood flow to regions with increased activity. The blood vessel dilation triggered by local, selective neural activity does not remain entirely local. From a vessel deep within the brain, the dilation propagates up along the vessel walls into a surface vessel and then down into other vessels that enter neighboring columns. Our team has just taken the first step, albeit an important one, in untangling the spatial precision of neurovascular coupling using very high-resolution imaging.

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