Abstract
We combined continuous theta-burst stimulation (cTBS) and resting state (RS)-fMRI approaches to investigate changes in functional connectivity (FC) induced by right dorsolateral prefrontal cortex (DLPFC)–cTBS at rest in a group of healthy subjects. Seed-based fMRI analysis revealed a specific pattern of correlation between the right prefrontal cortex and several brain regions: based on these results, we defined a 29-node network to assess changes in each network connection before and after, respectively, DLPFC–cTBS and sham sessions. A decrease of correlation between the right prefrontal cortex and right parietal cortex (Brodmann areas 46 and 40, respectively) was detected after cTBS, while no significant result was found when analyzing sham-session data. To our knowledge, this is the first study that demonstrates within-subject changes in FC induced by cTBS applied on prefrontal area. The possibility to induce selective changes in a specific region without interfering with functionally correlated area could have several implications for the study of functional properties of the brain, and for the emerging therapeutic strategies based on transcranial stimulation.
Highlights
IntroductionResting state (RS) fMRI is becoming one of the most popular techniques for assessing functional connectivity (FC) at rest [2, 3], while non-invasive brain stimulation methods can be used to probe how brain connectivity varies in response to an external perturbation
Brain connectivity has been non-invasively assessed in human subjects using techniques focused on three general network properties: anatomical connectivity, functional connectivity (FC), and response to perturbation/stimulation [1].Resting state (RS) fMRI is becoming one of the most popular techniques for assessing FC at rest [2, 3], while non-invasive brain stimulation methods can be used to probe how brain connectivity varies in response to an external perturbation
Seed-based connectivity analysis revealed a specific pattern of correlation between right dorsolateral prefrontal cortex (DLPFC) and several brain regions, including the right and left prefrontal, parietal, temporal cortex, precuneus, posterior cingulated cortex, thalamus, caudate nucleus, 3http://marsbar.sourceforge.net/ 4http://www.cmtk.org/viewer/documentation/users/tutorials/tut_nbs.html
Summary
Resting state (RS) fMRI is becoming one of the most popular techniques for assessing FC at rest [2, 3], while non-invasive brain stimulation methods can be used to probe how brain connectivity varies in response to an external perturbation. Seeded FC analyses demonstrated significant effects of rTMS on the prefrontal network dynamics in the n-back task that were not evident during rest [17] All these studies were performed with a strong working hypothesis, either testing only one resting state network (RSN) [15, 16] or using coupling analyses within a specified connection [17]. All of them compared the effects of rTMS in two separate sessions performed on different days, which could have increased the intrinsic variability of the FC measured by fMRI
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