Episodic Past, Future, and counterfactual thinking in Relapsing-Remitting Multiple sclerosis

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Multiple sclerosis (MS) is a progressive neurological disease affecting white matter.
• MS commonly causes motor deficits and cognitive impairments, including memory and future thinking.
• Episodic memory, future thinking, and counterfactual thinking share neural mechanisms, but counterfactual thinking in MS is understudied.

Purpose of the Study:

• To investigate episodic counterfactual thinking deficits in relapsing-remitting MS.
• To explore the association between white matter integrity in the default mode network (DMN) and these cognitive deficits.

Main Methods:

• Compared mental simulation task performance (past, future, counterfactual) in MS patients and controls.
• Utilized diffusion-weighted imaging (DWI) to assess white matter integrity in DMN-connected tracts.
• Analyzed fractional anisotropy, radial diffusivity, and streamline counts.

Main Results:

• MS patients showed reduced internal details in all simulations but no difference in external/semantic details.
• Patients reported lower composition ratings for counterfactual simulations compared to controls.
• Reduced white matter integrity in DMN tracts (superior longitudinal fasciculus, cingulum, inferior longitudinal fasciculus) was observed in MS patients.
• White matter integrity in these tracts predicted reduced internal details in counterfactual simulations.

Conclusions:

• Individuals with relapsing-remitting MS exhibit specific deficits in episodic counterfactual thinking.
• White matter integrity in DMN pathways is differentially associated with these deficits.
• Findings illuminate impairments in episodic simulation and its neural underpinnings in MS.