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The authors apologize for an error in the published version of the above article. In the visualization of deep brain stimulation contact point positions (Figure 1 and Supplementary Figure E), left and right were swapped. As a result, we wrongly stated that left-sided stimulation positions were correlated with the occurrence of post-operative apathy. Instead, this statement should have been made regarding right-sided stimulation positions. Since we did not elaborate on the lateralization of our results, the error did not affect the main conclusions of the article. Furthermore, the p-value displayed in Figure 1B did not match the p-value in the main text and the figure legend, which we have now corrected. We have now included the corrected versions of Figure 1 and Supplementary Figure E, as well as the corrections we have made to the main text:[Formula presented] Corrigendum Fig. 1 Stimulation locations of contact points in relation to change in apathy severityA) Stimulation locations in MNI-space (viewed from respectively dorsolateral left, posterior and dorsolateral right). The subthalamic nucleus (blue) and red nucleus (red) were added for reference purposes. Increases in apathy severity are color-coded, ranging from no increase (green/yellow) to strong increase (dark red). MNI, Montreal Neurological Institute; L, left; R, right.B) Stimulation locations were projected on a vector through the longitudinal axis of the STN, where negative values indicated more ventromedial stimulation positions. There was a significant correlation between stimulation position and increase in apathy severity for the right side (r(24) = 0.498, p = 0.010), but not for the left side (r(24) = 0.141, p = 0.491). [Formula presented] Corrigendum Supplementary Fig. E Stimulation locations of contact points in relation to improvement in motor score. Stimulation locations in MNI-space (viewed from respectively dorsolateral left, posterior and dorsolateral right). The subthalamic nucleus (blue) and red nucleus (red) were added for reference purposes. Improvements in motor score (% UPDRS-III, contrasting pre- versus post-DBS scores) are color-coded, ranging from no improvement (green/yellow) to strong improvement (dark red). Next, stimulation locations were projected on a vector through the longitudinal axis of the STN, where negative values indicated more ventromedial stimulation positions. There were no significant correlations between stimulation position and improvement in motor performance; left side (r(24) = 0.055, p = 0.788); right side (r(24) = −0.197, p = 0.335). MNI, Montreal Neurological Institute; L, left; R, right; UPDRS-III, Unified Parkinson's disease Rating Scale, motor part. Correction to abstract. The paragraph describing the results was changed into: “Results: …For the right hemisphere, increase in apathy was associated with a more dorsolateral stimulation location (p = 0.010) …” Correction to results. Apathy and DBS localization. This paragraph was changed into: “. There was a significant correlation between a more dorsolateral stimulation position (along a vector) and increase in apathy severity post-DBS for the right side (p = 0.010), but not for the left side (p = 0.491; Fig.1B). In contrast, there was no relationship between stimulation position (along the same vector) and the degree of improvement in total motor score (UPDRS-III; Supplementary Fig E). Next, we performed a hierarchical linear regression model using A backward elimination method to study the relationship between stimulation location and change in apathy score, including the following covariates: pre-to post-operative change in executive functioning, depression score, anxiety score, LEDD total, LEDD of dopamine agonist, and motor function. For the right side this resulted in the following model: R2 = 0.465; change in depression score, b(standardized) = 0.587, p = 0.039; stimulation position, b(standardized) = 0.727, p = 0.015. For the left side no statistically significant model could be fitted. Correction to discussion. The first paragraph of the discussion section was changed into: “.The pre-to-post-DBS increase in apathy severity was associated with a more dorsolateral position of the stimulation for the right hemisphere, …” The fourth paragraph of the discussion section was changed into: “. In addition, we observed a significant correlation between increase in pre-to-post DBS apathy score and a more dorsolateral stimulation location relative to the STN for the right hemisphere, but not for the left hemisphere. As the occurrence of apathy has previously not been related to laterality of DBS [45,46], we refrain from drawing any conclusions from this left-right difference.” The sixth paragraph of the discussion section was changed into: “… In our study increases in apathy severity were not associated with changes in executive functioning, whereas in the multiple regression model there was a relation between improvement in depression scores and better apathy scores after surgery (in the context of right-sided stimulation). It remains to be determined whether the occurrence of apathy after DBS has a cognitive or emotional-affective basis.” The final paragraph of the discussion section was changed into: “In conclusion, we found that increase in apathy severity after STN-DBS might well be an effect of the stimulation itself. Increased apathy severity scores correlated with a more dorsolateral stimulation location (right hemisphere) and with …”

In the original article, we neglected to include the funder, University of Zurich, UZHPostdoc Grant, grant no. [FK-19-040] to GF-G. The corrected Funding statement appears below. FUNDING This project was part of the research program “Characterization of functional brain network organization in dyslexia and development” funded by the Amsterdam Brain and Mind Project, a UvA-VUA Amsterdam Academic Alliance Initiative (https://www.abmp.eu/). Additional funding was received from University of Zurich, UZH Postdoc Grant, grant no. [FK-19-040] to GF-G. In the original article the email address of the corresponding author was incorrect. The correct email address is gorka.fragagonzalez@uzh.ch. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.

Additional file 1: The neural mass model. Single neural mass analyses. Parameter range. Table S1. Single neural mass model. Fig. S1. Example traces of simulated MEG signals in control condition and several AD-like (and their contrast) scenarios. Fig. S2. The excitatory and inhibitory post-synaptic potentials (EPSP and IPSP). Fig. S3. Neuronal activity and total power in AD-like and contrast scenarios in a single, uncoupled, neural mass model. Fig. S4. Simulated power spectra for AD-like and contrast scenarios in a single, not-coupled, neural mass model. Fig. S5. Robust changes in outcome measures over a range of values for each relevant model parameter.

In this study of early functional changes in Parkinson’s disease (PD), we aimed to provide a comprehensive assessment of the development of changes in both cortical and subcortical neurophysiological brain activity, including their association with clinical measures of disease severity. Repeated resting-state MEG recordings and clinical assessments were obtained in the context of a unique longitudinal cohort study over a seven-year period using a multiple longitudinal design. We used linear mixed-models to analyze the relationship between neurophysiological (spectral power and functional connectivity) and clinical data. At baseline, early-stage (drug-naïve) PD patients demonstrated spectral slowing compared to healthy controls in both subcortical and cortical brain regions, most outspoken in the latter. Over time, spectral slowing progressed in strong association with clinical measures of disease progression (cognitive and motor). Global functional connectivity was not different between groups at baseline and hardly changed over time. Therefore, investigation of associations with clinical measures of disease progression were not deemed useful. An analysis of individual connections demonstrated differences between groups at baseline (higher frontal theta, lower parieto-occipital alpha2 band functional connectivity) and over time in PD patients (increase in frontal delta and theta band functional connectivity). Our results suggest that spectral measures are promising candidates in the search for non-invasive markers of both early-stage PD and of the ongoing disease process.