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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 …”

BackgroundNotwithstanding the large improvement in motor function in Parkinson's disease (PD) patients treated with deep brain stimulation (DBS), apathy may increase. Postoperative apathy cannot always be related to a dose reduction of dopaminergic medication and stimulation itself may play a role.ObjectiveWe studied whether apathy in DBS-treated PD patients could be a stimulation effect.MethodsIn 26 PD patients we acquired apathy scores before and >6 months after DBS of the subthalamic nucleus (STN). Magnetoencephalography recordings (ON and OFF stimulation) were performed ≥6 months after DBS placement. Change in apathy severity was correlated with (i) improvement in motor function and dose reduction of dopaminergic medication, (ii) stimulation location (merged MRI and CT-scans) and (iii) stimulation-related changes in functional connectivity of brain regions that have an alleged role in apathy.ResultsAverage apathy severity significantly increased after DBS (p < 0.001) and the number of patients considered apathetic increased from two to nine. Change in apathy severity did not correlate with improvement in motor function or dose reduction of dopaminergic medication. For the left hemisphere, increase in apathy was associated with a more dorsolateral stimulation location (p = 0.010). The increase in apathy severity correlated with a decrease in alpha1 functional connectivity of the dorsolateral prefrontal cortex (p = 0.006), but not with changes of the medial orbitofrontal or the anterior cingulate cortex.ConclusionsThe present observations suggest that apathy after STN-DBS is not necessarily related to dose reductions of dopaminergic medication, but may be an effect of the stimulation itself. This highlights the importance of determining optimal DBS settings based on both motor and non-motor symptoms.