Multiple sclerosis impairs ability to detect abrupt appearance of a subliminal stimulus

The study was designed to find evidence that brain electrical activity associated with processing the abrupt appearance or disappearance of a sensory stimulus differed in the presence and absence of the neuropathological changes that are characteristic of multiple sclerosis (MS).

A subliminal stimulus (electrical field) was applied, and the onset and offset responses from patients with MS were compared with the responses of study participants in two age- and gender-matched control groups, using a novel type of non-linear dynamical analysis that had been developed in earlier studies.

An onset response occurred in 27% of the patients with MS, compared with 85% in the control groups. Among the three patients who exhibited onset-induced changes in brain electrical activity, the average latency of the effect was less and the magnitude of the change was greater than the corresponding values in the control group.

Non-linear analysis of electroencephalograms recorded during the sudden presentation of a subliminal stimulus potentially could serve as the basis of a functional test to help diagnose MS. A larger cohort of patients with MS needs to be assessed to validate the results of this study.