Multiple sclerosis language problems may be more than slowed thinking, study suggests

People with multiple sclerosis frequently report that words do not come as easily as they used to, yet standard neuropsychological assessments often fail to detect these expressive language difficulties. A study by researchers at Universitat Jaume I in Spain, working with a colleague at the Institute of Clinical Neuroscience of Southern Lugano in Switzerland, set out to determine whether such complaints reflect a general slowdown in cognitive processing or a more specific breakdown in word retrieval and semantic understanding. The findings, posted on the Frontiers in Behavioral Neuroscience site ahead of final formatted publication, suggest the latter: subtle lexical-semantic dysfunction may be a partially independent feature of the disease rather than a simple byproduct of slowed thinking.

The research team compared people with multiple sclerosis against healthy controls on specialized naming and semantic judgment tasks from the Cambridge Language Battery. The study used specialized naming and semantic judgment tasks from the Cambridge Language Battery, with the naming tasks addressing lexical access and the synonym judgment task addressing semantic processing. The researchers measured both performance level and reaction times across the tasks, capturing how accurately participants responded and how quickly.

The results showed a dissociation between speed and accuracy. Both groups achieved high levels of accuracy across the tasks, meaning that people with multiple sclerosis were not failing outright at word retrieval or semantic judgment. However, the patient group took significantly longer to respond on every task, with large and consistent effect sizes. On its own, this pattern is consistent with the generalized cognitive slowing the study set out to test. But the researchers went further, using robust regression models to ask whether general cognitive factors could explain away the language differences.

Those models incorporated measures of information processing speed, working memory, and verbal fluency. When the outcome was reaction time, general cognitive factors explained a substantial proportion of the variance. General cognitive factors, particularly baseline information processing speed, explained between 22 and 51 percent of the variance in how quickly participants responded. After statistically adjusting for these factors, the between-group differences in reaction time were largely reduced across all tasks. In other words, the delayed responding seen in the multiple sclerosis group appears to be largely explained by general cognitive factors, particularly baseline information processing speed, rather than by anything specific to language itself.

Accuracy showed a different pattern. Performance on the synonym judgment task was primarily related to semantic and phonemic fluency, and once the influence of those variables was statistically accounted for, the differences between people with multiple sclerosis and healthy controls were largely reduced.

The naming tasks, however, were not explained by these cognitive predictors. Even the best combination of the cognitive predictors tested explained less than 10 percent of the variance in accuracy on these tasks. More telling still, the group differences in naming accuracy remained largely unchanged after adjustment.

This dissociation between speed and accuracy forms the core of the study’s argument. General cognitive slowing, the researchers conclude, drives delayed responding but fails to account for reduced accuracy on demanding language tasks. That pattern implies that subtle lexical-semantic dysfunction represents a partially independent feature of multiple sclerosis.

Subject of Research: Lexical-semantic language impairment in multiple sclerosis and its dissociation from generalized cognitive slowing

Article Title: Beyond cognitive slowing: potential evidence for specific lexical-semantic impairment in multiple sclerosis

Article References: Forn, C., Félix-Esbrí, S., Mercado Gil, N., Zaragoza Mezquita, M., Riccitelli, G. C., Visser, M., & Sanchis Segura, C. (2026). Beyond cognitive slowing: potential evidence for specific lexical-semantic impairment in multiple sclerosis. Frontiers in Behavioral Neuroscience, 20, Article 1991139. https://doi.org/10.3389/fnbeh.2026.1991139

Image Credits: AI Generated

DOI: 10.3389/fnbeh.2026.1991139

Keywords: multiple sclerosis, lexical access, semantic processing, naming tasks, reaction time, cognitive slowing, neuropsychological assessment, verbal fluency, working memory, processing speed, Cambridge Language Battery, expressive language