109 Etiology in Lesion-Symptom Mapping: Tumor vs. Stroke Stroke patients The data from the stroke patients was gathered as part of the Functional Architecture of the Brain for Vision (FAB4V) study, which is a multi-center prospective cohort study investigating vision and cognition after ischemic stroke. Adult patients with a first-ever symptomatic cerebral ischemic stroke were included in the current study. Written informed consent was obtained from all participants prior to participation. Neurocognitive assessment and an MRI including a T2 FLAIR were performed between three weeks and three months post-infarction. A maximum of one week was allowed between the neurocognitive assessment and the MRI. Data collection Neurocognitive assessment The neuropsychological instruments and corresponding scores for both populations are listed in Supplementary Table 1, along with full test descriptions. The uncorrected scores for each test were transformed into z-scores based on the mean and standard deviation of control populations derived from published norm data. For descriptive purposes, a cognitive impairment was defined as a z-score equal to or lower than -1.5. To assess differences between the tumor and stroke group regarding cognitive performance two types of statistics were performed. Firstly, using Pearson’s chi-square tests we investigated whether the relative number of patients with a cognitive impairment was higher in the tumor or stroke group for any of the available cognitive tasks. Secondly, using two-samples t-tests we investigated whether the cognitive performance of the tumor group differed from that of the stroke group for the cognitive tasks that were used in subsequent LSM analyses. For the LSM analyses, we selected two internationally widely used, standardized psychometric instruments: the Rey Auditory Verbal Learning Test (RAVLT), a verbal learning and memory test that taps into multiple aspects of memory (direct recall, delayed recall, and delayed recognition) and the Verbal Fluency Test. The fluency test is separated into a phonemic fluency (Dutch versions of the Controlled Oral Word Association Test) and semantic fluency (animal) part. The phonemic fluency test is thought to rely more heavily on executive control, while the semantic fluency test is more dependent on correct retrieval of semantic knowledge. The RAVLT and Verbal Fluency Test require both overlapping and distinct cognitive concepts, thereby allowing for specificity in lesion-symptom associations. Patient characteristics Patient characteristics for the tumor patients were extracted from the electronic patient file. This data included sex, age at time of surgery, level of education, 5
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