Brain connectivity
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The effects of transcranial pulsed current stimulation (tPCS) on resting state functional connectivity (rs-FC) within the motor network were investigated. Eleven healthy participants received one magnetic resonance imaging (MRI) session with three resting state functional MRI (rs-fMRI) scans, one before stimulation (PRE-STIM) to collect baseline measures, one during stimulation (STIM), and one after 13 min of stimulation (POST-STIM). Rs-FC measures during the STIM and POST-STIM conditions were compared to the PRE-STIM baseline. ⋯ Bivariate measures of connectivity demonstrate reduced strength of connectivity for the whole network average (p=0.044) and reduced diversity of connectivity for the network average during stimulation (p=0.024). During the POST-STIM condition, the trend of reduced diversity for the network average was statistically weaker (p=0.071). In conclusion, while many of the findings are comparable to previous reports using simultaneous transcranial direct current stimulation (tDCS) and fMRI acquisition, we also demonstrate additional changes in connectivity patterns that are induced by tPCS.
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Functional brain networks are sets of cortical, subcortical, and cerebellar regions whose neuronal activities are synchronous over multiple time scales. Spatial independent component analysis (sICA) is a widespread approach that is used to identify functional networks in the human brain from functional magnetic resonance imaging (fMRI) resting-state data, and there is now a general agreement regarding the cortical regions involved in each network. It is well known that these cortical regions are preferentially connected with specific subcortical functional territories; however, subcortical components (SC) have not been observed whether in a robust or in a reproducible manner using sICA. ⋯ Second, these networks are complemented with related subcortical areas based on the similarity of their time courses, using an individual general linear model and a random-effect group analysis. Two independent resting-state fMRI datasets were processed, and the SC of both datasets overlapped by 69% to 99% depending on the network, showing the reproducibility and the robustness of our approach. The relationship between SC and functional cortical networks was consistent with functional territories (sensorimotor, associative, and limbic) from an immunohistochemical atlas of the basal ganglia.