Summary: A new study reports that when at rest, neural networks are ready to execute even the simplest of behaviors and movements.
Source: Wayne State University.
Just as a sprinter’s body and muscles are ready for action as they wait for the starting gun to fire, brain networks at rest appear to be waiting in a state of potentiation to execute even the simplest of behaviors.
This evidence comes from a new paper published this week in the journal PLoS One, reporting on a study led by professors Vaibhav Diwadkar, Ph.D., at Wayne State University’s School of Medicine and Steven L. Bressler, Ph.D., interim director of Florida Atlantic University’s Center for Complex Systems and Brain Sciences.
In the study, “Potentiation of motor sub-networks for motor control but not working memory: Interaction of dACC and SMA revealed by resting-state directed functional connectivity,” the researchers used a simple experimental task, having each participant perform a simple motor control behavior (tapping their forefinger to a visual cue) that alternated between behavior and rest. Brain activity was acquired using functional MRI (fMRI), a technique that allows collection of dynamic signals from within the brain when the subject is doing a task as well as when they are at rest.
Using relatively complex modeling of fMRI signals, the team studied brain network interactions between two important brain regions: the dorsal anterior cingulate cortex (dACC), used for control, and the supplementary motor area (SMA), used for motor movements. In their previous studies, the team highlighted the importance of directional network interactions from the dACC to the SMA during simple motor behavior. In the PLoS One paper, they showed a compelling and opposite effect: during the rest periods that alternated between the motor behavior task, network interactions from the SMA to the dACC were now increased.
According to Diwadkar, who co-directs the Brain Imaging Research Division in the Department of Psychiatry & Behavioral Neurosciences, “These results suggest that directional interactions from the SMA to the dACC during the rest period may in fact potentiate task-related interactions in the opposite direction.” He further noted that the studies confirm what has been long suggested and independently demonstrated: that the brain’s networks are always in a state of potentiation for action, precisely because it is impossible to predict what they will be required to do at any given time. Therefore, it is unlikely that the brain can ever be at true rest.
This paper is one of the few attempts to systematically investigate directional interactions between brain networks in the resting state and show how this state might potentiate the opposite direction of the same network task-related processing.
“Our findings are compelling because brain networks are in patterns of incessantly complex directional interactions,” said Diwadkar. “Directionality is difficult to measure, and our complex analyses show that it is possible to estimate this from fMRI data.”
According to Diwadkar, the team’s findings reveal aspects not only of normative brain function but may also provide new directions for characterizing disordered network interactions in neuropsychiatric syndromes. They will be investigating these questions in obsessive-compulsive disorder with David Rosenberg, M.D., the Miriam L. Hamburger Endowed Chair of Child Psychiatry and chair of the Department of Psychiatry and Behavioral Neurosciences at Wayne State University; and in schizophrenia with Dr. Jeffrey Stanley, Ph.D., associate professor of psychiatry. Diwadkar and Bressler are continuing to collaborate on several directions of research focusing on brain network function and dysfunction.
Funding: Diwadkar’s research has been funded by the National Institutes of Health (grant numbers: MH068680, MH111177 and MH059299).
Source: Julie O’Connor – Wayne State University
Image Source: NeuroscienceNews.com image is credited to credited to Diwadkar et al./PLOS ONE..
Original Research: Full open access research for “Potentiation of motor sub-networks for motor control but not working memory: Interaction of dACC and SMA revealed by resting-state directed functional connectivity” by Vaibhav A. Diwadkar, Avisa Asemi, Ashley Burgess, Asadur Chowdury, and Steven L. Bressler in PLOS ONE. Published online March 9 2017 doi:10.1371/journal.pone.0172531
Potentiation of motor sub-networks for motor control but not working memory: Interaction of dACC and SMA revealed by resting-state directed functional connectivity
The dorsal Anterior Cingulate Cortex (dACC) and the Supplementary Motor Area (SMA) are known to interact during motor coordination behavior. We previously discovered that the directional influences underlying this interaction in a visuo-motor coordination task are asymmetric, with the dACC→SMA influence being significantly greater than that in the reverse direction. To assess the specificity of this effect, here we undertook an analysis of the interaction between dACC and SMA in two distinct contexts. In addition to the motor coordination task, we also assessed these effects during a (n-back) working memory task. We applied directed functional connectivity analysis to these two task paradigms, and also to the rest condition of each paradigm, in which rest blocks were interspersed with task blocks. We report here that the previously known asymmetric interaction between dACC and SMA, with dACC→SMA dominating, was significantly larger in the motor coordination task than the memory task. Moreover the asymmetry between dACC and SMA was reversed during the rest condition of the motor coordination task, but not of the working memory task. In sum, the dACC→SMA influence was significantly greater in the motor task than the memory task condition, and the SMA→dACC influence was significantly greater in the motor rest than the memory rest condition. We interpret these results as suggesting that the potentiation of motor sub-networks during the motor rest condition supports the motor control of SMA by dACC during the active motor task condition.
“Potentiation of motor sub-networks for motor control but not working memory: Interaction of dACC and SMA revealed by resting-state directed functional connectivity” by Vaibhav A. Diwadkar, Avisa Asemi, Ashley Burgess, Asadur Chowdury, and Steven L. Bressler in PLOS ONE. Published online March 9 2017 doi:10.1371/journal.pone.0172531