Social memory deficits and their neural correlates in multiple sclerosis.

While the impact of multiple sclerosis (MS) on various cognitive functions has been well documented, social memory - memory of other individuals - remains unexplored. In this study, 26 MS patients and 23 healthy controls underwent task-based fMRI during a social navigation paradigm simulating interpersonal interactions, followed by an episodic social memory recall questionnaire. T1-weighted, T2-FLAIR and diffusion tensor imaging were also acquired. As social navigation metrics have been associated with activity in the precuneus/posterior cingulate cortex (PPCC), we examined this region's functional and volumetric correlates, as well as T2-FLAIR hyperintense white matter lesion burden and microstructural abnormalities in normal-appearing white matter. MS patients showed preserved social navigation but impaired episodic social memory (p = 0.003). No task-based functional differences were observed between groups. However, impaired recall in MS was associated with reduced right PPCC volume (p = 0.032), greater volume (p = 0.002) and number (p = 0.017) of T2-FLAIR hyperintense lesions, and altered integrity of normal-appearing white matter, indexed by lower fractional anisotropy (p < 0.001) and higher mean diffusivity (p = 0.019). These findings suggest a novel cognitive deficit in MS and underscore the potential relevance of regional brain volume and white matter pathology to social memory, informing future studies of social cognition in MS and other neuropsychiatric disorders.