Multivariate Connectome-Based Symptom Mapping in Post-Stroke Patients: Networks Supporting Language and Speech

Abstract

Language processing relies on a widespread network of brain regions. Univariate post-stroke lesion-behavior mapping is a particularly potent method to study brain-language relationships. However, it is a concern that this method may overlook structural disconnections to seemingly spared regions and may fail to adjudicate between regions that subserve different processes but share the same vascular perfusion bed. For these reasons, more refined structural brain mapping techniques may improve the accuracy of detecting brain networks supporting language. In this study, we applied a predictive multivariate framework to investigate the relationship between language deficits in human participants with chronic aphasia and the topological distribution of structural brain damage, defined as post-stroke necrosis or cortical disconnection. We analyzed lesion maps as well as structural connectome measures of whole-brain neural network integrity to predict clinically applicable language scores from the Western Aphasia Battery (WAB). Out-of-sample prediction accuracy was comparable for both types of analyses, which revealed spatially distinct, albeit overlapping, networks of cortical regions implicated in specific aspects of speech functioning. Importantly, all WAB scores could be predicted at better-than-chance level from the connections between gray-matter regions spared by the lesion. Connectome-based analysis highlighted the role of connectivity of the temporoparietal junction as a multimodal area crucial for language tasks. Our results support that connectome-based approaches are an important complement to necrotic lesion-based approaches and should be used in combination with lesion mapping to fully elucidate whether structurally damaged or structurally disconnected regions relate to aphasic impairment and its recovery.

Revealing the dual streams of speech processing

“…For example, it has been shown amply that damage to posterior regions, such as the posterior STG, results in disordered speech production (38,39). This fact is, indeed, shown in patients with Wernicke's aphasia, a disorder caused by damage to the posterior regions of the temporal lobe (40), who suffer from severely impaired speech comprehension as well as impaired speech production marked by neologisms, phonemic paraphasias, and semantic paraphasias. Although these patients present with fluent speech production, the content of their speech is affected because of damage to the ventral stream.…”

Mapping the contribution and strategic distribution patterns of neuroimaging features of small vessel disease in poststroke cognitive impairment

“…In fact, their different performance resulted from the mechanisms of these two schemes. While TO feature selection discarded the features that were not highly correlated with a given behavioural score, it could potentially discard the features that might be predictive when used in combination with other features at the same time 12. In contrast, TS feature selection additionally considered the intercorrelations among the features and their multivariate relationship with the behaviour score.…”

“…In detail, we attempted two feature selection schemes: one that only captures the task-oriented (TO) information (only screens the predictors that each have independent contributions to the outcome),12 and the other captures both the TO and self-representation (TS) information (screens the predictors that jointly have contribution to the outcome) 22. Model training was subsequently implemented for the SVR models preprocessed with different feature selection schemes.…”

Ontogenetic Development of Neurophysiological Mechanisms Underlying Language Processing

“…It is a learned phenomenon driven over time by large-scale, spatially distributed neural networks seeking to efficiently maximize processing, storage, and manipulation of information for cognitive and behavioral operations." Yourganov et al [45] also pointed out that connectome-based approaches should be used in combination with lesion-based ones to fully elucidate whether structurally damaged or disconnected regions relate to the aphasic impairment and its recovery.…”