131 Electrophysiological effects of deep brain stimulation in anorexia nervosa frequency: lower alpha peak frequency counteracts any power increase in the upper alpha band while increasing the effect in the lower alpha band/theta band. Effect of DBS on connectivity measures To characterize changes in spatial structure across time (within AN) and between subjects (AN vs HC), we calculated coherence and the weighted phase lag index (wPLI) as measures of connectivity between all possible pairs of electrodes. Figure 5 (top row) shows the connectivity for coherence in the four regions, while figure 5 (bottom row) shows connectivity estimated with wPLI. For each region, the cross-spectra of all electrodes within that region with all other electrodes were averaged (ignoring connections closer than 4 cm in a standard spherical head model of 8.5 cm radius to reduce spurious connectivity due to volume conduction effects (34)). All spectra showed clear peaks in the alpha band. Many spectra also showed beta band peaks in connectivity, although these were more prominent in the T1 and T4 periods. This suggests that the alpha and lower beta bands are important oscillation frequencies for default-mode communication. Figure 5. Connectivity spectra averaged over channels within a region. (Top row) Coherence spectra of AN showed clear peaks at T1 in the alpha and beta bands. T2 reduced peak size and increased resemblance to HC (grey). T4 showed re-emergence of the alpha and beta peaks in all four regions, albeit with slightly increased frequency. Posterior areas showed reduced connectivity in all groups. (Bottom row) weighted Phase Lag Index (wPLI) spectra showed a similar pattern to coherence spectra for connectivity between left temporal-parietal to right frontal areas. No clear regional differences were observed.
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