Time perception impairment in multiple sclerosis patients: a survey on internal clock model.

Time perception is known as a mental ability to discern time. Although relative nature of time leaves its numerous aspects undefined, several models have been developed to describe temporal information processing in the brain as well as several areas of the brain have shown to be involved. Time perception alteration has been reported in several neurological conditions; however, the effect of multiple sclerosis (MS) on time perception has yet to be explained. In this study, we aimed to investigate the domains of temporal processing involved in patients with MS and the probable factors affecting it, such as the location of brain demyelinating plaques and gender. Two groups of participants (MS: n  = 27 (8 men, 19 women), mean age = 33.85; control: n  = 30 (10 men, 20 women), mean age = 28.46) were asked to perform quadruplet time perception tasks (prospective time estimation, duration discrimination, temporal reproduction, and paced motor timing) designed with a software program. Patients with MS had significantly higher scores in time estimation ( p  < 0.01) and duration discrimination ( p  < 0.001, in 100-ms interval; p  < 0.05, in 1000-ms interval), indicating that MS patients overestimate the time. Since a slower internal clock for MS patients was expected as a result of axonal demyelination, these results suggest the time overestimation in patients with MS which is in contrast with the internal clock model. It means that a slow internal clock causes underestimating and perceiving the time slower.