Biology subjects

Karnath, H.-O.

Publications and source records attributed to Karnath, H.-O..

22 records · Page 2Linked to original sources

bioRxiv2019

Using machine learning-based lesion behavior mapping to identify anatomical networks of cognitive dysfunction: spatial neglect and attention

Previous lesion behavior studies primarily used univariate lesion behavior mapping techniques to map the anatomical basis of spatial neglect after right brain damage. These studies led to inconsistent results and lively controversies. Given these inconsistencies, the idea of a widespread network that might underlie spatial orientation and neglect has been pushed forward. In such case, univariate lesion behavior mapping methods might have been inherently limited in uncover the presumed network in a single study due to limited statistical power. By using multivariate lesion-mapping based on support vector regression, we aimed to validate the network hypothesis directly in a large sample of 203 newly recruited right brain damaged patients. In a single analysis, this method identified a network of parietal, temporal, frontal, and subcortical regions, which also included white matter tracts connecting these regions. The results were compared to univariate analyses of the same patient sample using different combinations of lesion volume correction and statistical thresholding. The comparison revealed clear benefits of multivariate lesion behavior mapping in identifying brain networks.

neuroscience↗

bioRxiv2019

The network underlying human higher-order motor control: Insights from machine learning-based lesion-behaviour mapping in apraxia

Neurological patients with apraxia of pantomime provide us with a unique opportunity to study the neural correlates of higher-order motor function. Previous studies using lesion-behaviour mapping methods led to inconsistent anatomical results, reporting various lesion locations to induce this symptom. We hypothesised that the inconsistencies might arise from limitations of mass-univariate lesion-behaviour mapping approaches if our ability to pantomime the use of objects is organised in a brain network. Thus, we investigated apraxia of pantomime by using multivariate lesion behaviour mapping based both on support vector regression and sparse canonical correlations in a sample of 130 left-hemisphere stroke patients. Both multivariate methods identified multiple areas to underlie high-order motor control, including inferior parietal lobule, precentral gyrus, posterior parts of middle temporal cortex, and insula. Further, long association fibres were affected, such as the superior longitudinal fascicle, inferior occipito-frontal fascicle, uncinated fascicle, and superior occipito-frontal fascicle. The findings thus not only underline the benefits of multivariate lesion-behaviour mapping in brain networks, but they also uncovered that higher-order motor control indeed is based on a common anatomical network.

neuroscience↗

bioRxiv2018

An empirical evaluation of multivariate lesion behaviour mapping using support vector regression

Multivariate lesion behaviour mapping based on machine learning algorithms has recently been suggested to complement the methods of anatomo-behavioural approaches in cognitive neuroscience. Several studies applied and validated support vector regression-based lesion symptom mapping (SVR-LSM) to map anatomo-behavioural relations. However, this promising method, as well as the multivariate approach per se, still bears many open questions. By using large lesion samples in three simulation experiments, the present study empirically tested the validity of several methodological aspects. We found that i) correction for multiple comparisons is required in the current implementation of SVR-LSM, ii) that sample sizes of at least 100 to 120 subjects are required to optimally model voxel-wise lesion location in SVR-LSM, and iii) that SVR-LSM is susceptible to misplacement of statistical topographies along the brains vasculature to a similar extent as mass-univariate analyses.

neuroscience↗

bioRxiv2018

Right-sided brain lesions predominate among patients with lesional mania: evidence from a systematic review and pooled lesion analysis

BackgroundDespite claims that lesional mania is associated with right-hemisphere lesions, supporting evidence is scarce, and association with specific brain areas has not been demonstrated.\n\nAimsTo test whether focal brain lesions in lesional mania are more often right-than left-sided, and if lesions converge on areas relevant to mood regulation.\n\nMethodsWe performed a systematic literature search (PROSPERO registration CRD42016053675) on PubMed and Web-Of-Science, using terms that reflected diagnoses and structures of interest, and lesional mechanisms. Two researchers reviewed the articles separately according to PRISMA Guidelines, to select reports of adult-onset hypomania, mania or mixed state following a focal brain lesion. When available, eligible lesion images were manually traced onto the corresponding slices of MNI space, and lesion topography analyzed using standard brain atlases. Pooled-analyses of individual patient data were performed.\n\nResultsData from 207 lesional mania patients was extracted from 110 reports. Among patients with focal lesions (N=197) more patients had lesions involving the right (84.3%) than the left (34.5%) hemisphere. Among 54 lesion images that were available, right-sided predominance of lesions was confirmed, and found to be was conserved across multiple brain regions, including the temporal lobe, fusiform gyrus and thalamus. These, in addition to several frontal lobe areas, were also identified as preferential lesion sites in comparisons with control lesions.\n\nConclusionsPooled-analyses, based on the most comprehensive dataset of lesional mania available to date, confirm a preferential association with right-hemisphere lesions, while suggesting that several brain areas/circuits, relevant to mood regulation, are most frequently affected.

neuroscience↗