Connecting the Dots with functional connectivity MRI
by Rebecca Steinberg
When we perform an action, such as raising a glass of water, we recognize that several cognitive actions are at play. We must visualize the glass, perceive its location, and then maneuver our arm in the orientation to best grasp the object. It has been firmly established in our scientific understanding of proprioception and our interactions with our environment that there must exist some cognitive connectivity leading to holistic movement.
But how can we best make these connections evident? One tool many scientists have depended on is fcMRI, or functional connectivity magnetic resonance imaging. The rationale behind this method is simple. Different regions of the brain are presumed “connected” when they appear active in response to a given stimulus. However, a recent review by Buckner et al. suggests that the data gathered from fcMRI may not serve as sound evidence for the broad claims they endorse.
Cases in which a portion of the brain is damaged or not present demonstrate that the entire brain does not need to be intact to perform specific functions. While this suggests that specific pathways do exist within the brain leading to function, is there a possibility that tissues can heal or compensate for missing connections through the generation of new pathways? fcMRI does not account for or readily show the unknown, multiple pathways dedicated to the same function.
Similarly, when examining fcMRI results, Buckner et al. point out the apparent effects of individual experience and personal development on brain activity. Subjects may respond in different manners to the same stimulus. Even when tested at rest, when it appears all human minds would possess similar brain activity, certain individualistic elements, such as head motion and proneness to anxiety, may lead to deceiving observed brain activity trends.
fcMRI raises more questions for researchers examining brain connectivity. Though it is convenient to identify “regions” of the brain, fcMRI begs the question of whether these areas of activity exist, or if they are more likely bundles of individual pathways that follow a coincidental route in the brain. Beckner, et al. suggest that fcMRI should not be a tool used to generate answers, but to propose new questions concerning connectivity.
However, many findings have been brought to the attention of researchers by fcMRI. The ability to examine activity across the entire brain as opposed to a small portion has led researchers to recognize that certain locations in the brain do in fact activate in response to a stimulus, though the methods behind this observation are still mystifying.
At the same time, the relations between these apparent networks are highlighted through imaging in a way previously unavailable. By examining the presence of “anticorrelation” between brain connections, opposing pathways are activated to either undergo or avoid a response to stimuli. Despite these significant cognitive findings, alternative methods are required to elucidate this data.
Because of the potential pitfalls fcMRI is subject to, Buckner et al. suggest that rather than using fcMRI as evidence for proposed connective theory, the imaging technique instead be used as a launching point for further research, to be justified by more comprehensive means. fcMRI might serve as an incredible tool to bring attention to cognitive pathways previously unknown, but extensive research and alternative methods are required to fully accept any related connectivity theories.
References:
Buckner, R. L., Krienen, F. M., and Yeo, B. T. T. (2013). Opportunities and limitations of intrinsic functional connectivity MRI. Nature Nueroscience 16(7): 832-837.
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