University of Twente Student Theses
Assessing changes in EEG functional connectivity after dual-site transcranial Alternating Current Stimulation for varied phase lags
Jong, B.Z. de (2024) Assessing changes in EEG functional connectivity after dual-site transcranial Alternating Current Stimulation for varied phase lags.
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| Abstract: | Background: Functional connectivity (FC) is known to be altered in various neurological disorders. Dual-site transcranial Alternating Current Stimulation (tACS) is hypothesized to modulate FC, potentially improving motor-related symptoms when targeted at the primary motor cortex (M1). Our main objective was to investigate the phase lag condition because it is a fundamental parameter in dual-site tACS to modulate FC. However, the specific effects of the phase lag remain poorly understood, as there is high variability in results. In addition, only in-phase and anti-phase conditions have been previously investigated. Furthermore, the optimal method for measuring FC and the appropriate dual-site tACS parameter settings remain ambiguous. Therefore, our secondary objective is to systematically analyze FC measures and parameter settings to recommend the most effective configurations for future research. Methods: In this study, we have measured resting-state EEG to investigate the impact of dual-site tACS on the beta-band FC between bilateral M1s by examining four phase lag conditions and a sham condition for nine healthy young participants (aged 18-34 years). The four phase lags were used: 0 (in-phase, IP), π/2 (pi-half, PH), π (anti-phase, AP), and 3π/2 (three-half-pi, 3HP). Circular statistics, using the Mean Vector Length (MVL) in conjunction with permutation statistics, were employed to assess uniformity across the phase lags while averaging the observed change in FC across all participants for each phase lag condition. Subsequently, multiple comparisons tests, including Bonferroni-correction, were conducted between all five conditions. The statistical tests were performed for ImCoh and wPLI, across four parameter settings: electrode pair selection, frequency band, epoch length, and averaging type. Results: For an average over three electrode pairs (FCC3h-FCC4h, C5-C6, and FC5-FC6), a beta-band frequency range of 13-30 Hz, an epoch length of 20s, using averaging type 1, we observe a significant non-uniform distribution across the four phase lags. This was found for wPLI (p=0.017), but not for ImCoh (p=0.187). Subsequent multiple comparisons tests revealed a significant difference between SH-AP (p=0.039) and IP-AP (p=0.022). These differences were due to a relative increase in FC for AP. Conclusions: Our dual-site tACS study, which investigated four types of phase lags, has revealed the uncommon finding of increased FC for AP compared to IP and SH. This result underscores the variability in phase lag outcomes in dual-site tACS, highlighting the need for further investigation. As we found significant results for wPLI where ImCoh did not, we suggest using wPLI over ImCoh as the FC measure. Additionally, we identified a different electrode pair group for capturing changes in FC than initially expected. Further investigation in our ongoing study, incorporating spatial filtering, source reconstruction, and a larger sample size, is warranted to enhance the statistical power and reliability of these findings. |
| Item Type: | Essay (Master) |
| Faculty: | TNW: Science and Technology |
| Subject: | 44 medicine, 53 electrotechnology |
| Programme: | Biomedical Engineering MSc (66226) |
| Link to this item: | https://purl.utwente.nl/essays/100016 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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