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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.

Background Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system. This study aimed to evaluate the advantages and disadvantages of a positron emission tomography (PET) scan method for diagnosing Alzheimer’s disease (AD) in MS patients with no clinical symptoms or early-onset AD. Main text To identify potentially relevant documents, we systematically searched international databases from 2000 to 2021. We abstracted data on article characteristics, ID/country, study, design, population, type of tracer, and outcomes. The primary outcomes were mean amyloid tracer standardized uptake value relative (SUVr), AD diagnosis in MS patients, and the tracer's uptake. Secondary outcomes were the megabecquerel amount of tracer and tracer side effects. Nine studies were finally entered into our research for review. Among the studies included, two studies used 18F-florbetaben, six of these used 11C-Pittsburgh compound B (11C-PiB), and in two studies (18)F‑florbetapir (18F-AV1451) was used for imaging. Data from 236 participants were included in this study (145 MS patients, 17 AD patients, 12 mild cognitive impairment patients, and 62 healthy controls). Conclusions PET scan, especially florbetapir-based radio traces in helping to diagnose early AD, is imperative to use an age-specific cutoff in MS patients to support AD diagnosis.