Test-retest reliability of prefrontal transcranial Direct Current Stimulation (tDCS) effects on functional MRI connectivity in healthy subjects.

Neuroimage. 2017 Apr 24;:

Authors: Wörsching J, Padberg F, Helbich K, Hasan A, Koch L, Goerigk S, Stoecklein S, Ertl-Wagner B, Keeser D

Abstract
Transcranial Direct Current Stimulation (tDCS) of the prefrontal cortex can be used for probing functional brain connectivity and meets general interest as novel therapeutic intervention in psychiatric and neurological disorders. Along with a more extensive use, it is important to understand the interplay between neural systems and stimulation protocols requiring basic methodological work. Here, we examined the test-retest (TRT) characteristics of tDCS-induced modulations in resting-state functional-connectivity MRI (RS fcMRI). Twenty healthy subjects received 20minutes of either active or sham tDCS of the dorsolateral prefrontal cortex (2mA, anode over F3 and cathode over F4, international 10-20 system), preceded and ensued by RS fcMRI (10minutes each). All subject underwent three tDCS sessions with one-week intervals in between. Effects of tDCS on RS fcMRI were determined at an individual as well as at a group level using both ROI-based and independent-component analyses (ICA). To evaluate the TRT reliability of individual active-tDCS and sham effects on RS fcMRI, voxel-wise intra-class correlation coefficients (ICC) of post-tDCS images between testing session were calculated. For both approaches, results revealed low reliability of RS fcMRI after active tDCS (ICC(2,1) = -0.09 - 0.16). Reliability of RS fcMRI (baselines only) was low to moderate for ROI-derived (ICC(2,1) = 0.13 - 0.50) and low for ICA-derived connectivity (ICC(2,1) = 0.19 - 0.34). For ROI-based analyses, the distribution of voxel-wise ICC was shifted to lower TRT reliability after active, but not after sham tDCS where the distribution was similar to baseline. This shift was not observed for whole RS networks (ICA). The intra-individual variation observed here resembles variability of tDCS effects in motor regions and raises further questions regarding sources of variability and localisation of tDCS effects. Moreover, the data can be used for appropriately designing large scale studies investigating these methodological issues.

PMID: 28450138 [PubMed - as supplied by publisher]