People with multiple sclerosis (MS) may have cognitive defects that cannot be detected using conventional paper-and-pen tests but that can be assessed with computer-based tests, a new study shows.
The findings also indicate that people with MS may be more susceptible to cognitive impairment when the brain has to address increased task demands.
An estimated 40%–70% of people with MS will experience some form of cognitive impairment, with the most common being reduced information processing speed (IPS) — which is the speed at which the brain can make sense of and respond to new information.
Traditionally, reduced IPS has been measured using pencil-and-paper tests, such as the Symbol Digit Modalities Test (SDMT). However, these tests may not be sensitive enough to detect relatively small impairments.
A growing body of research suggests that computer-based tests can be used to more sensitively measure delayed IPS in people with MS.
Now, researchers at the University of Verona, in Italy, created a tablet-based video game to measure IPS.
“Testing IPS in different cognitive load conditions by using computerized tools might reveal initial IPS slowness underestimated by classic paper-and-pencil tests,” the team wrote.
Specifically, the researchers were interested in the role of cognitive load on IPS in people with MS.
Cognitive load is the amount of information that the brain has to handle at one time. Previous research suggested that people with MS may have particular difficulties completing tasks with a high cognitive load. Basically, the rationale is that when there is little information for the brain to handle, a brain with slight cognitive impairment can compensate for that impairment, but the impairment becomes evident when cognitive load is increased to the point that the brain is no longer able to compensate.
The video game designed by the team shows a cartoon building with nine windows, at which different “people” will appear. Players are instructed to tap a particular person as quickly as they can.
Cognitive load is increased by having more people at the windows, then by having more similarity between the people so it becomes harder to find the exact one that should be tapped. The game has three levels, corresponding to low, medium, and high visual-attentional cognitive load.
The game uses reaction time and accuracy to measure IPS.
The researchers tested their game on 51 people with MS (mean age 36.7 years) who had no evidence of cognitive impairment on paper-and-pen tests. For comparison, 20 people without MS, who were similar to the MS group in terms of age and other parameters, were also assessed.
In both groups, mean reaction time increased, while accuracy decreased, when cognitive load was higher.
Notably, two groups had statistically significant differences in scores: people with MS had a significantly longer reaction time at low cognitive load (508.5 milliseconds) and medium cognitive load (631.1 ) compared to controls (462.3 milliseconds for low cognitive load and 581 milliseconds for medium). However, no significant differences in reaction time were observed between the groups at high cognitive load.
In addition, people with MS were significantly less accurate at high cognitive load (score of 45.9) compared to the control group (55.4 score), but accuracy was not significantly different between the groups at low or medium cognitive load.
Statistical analyses indicated high cognitive load correlated significantly with accuracy, but not with reaction time.
MS patients “showed a significantly more pronounced decrement in accuracy as a function of the visual-attentional load, suggesting a higher susceptibility to increased task demands,” the researchers wrote.
Although none of the people with MS were cognitively impaired based on the SDMT, there were significant correlations between SDMT scores and video game scores. In other words, statistically, people with worse SDMT scores were more likely to have higher reaction time and lower accuracy on the video game.
“The results highlighted that the videogame was able to detect a more pronounced IPS slowness as a function of cognitive load in [people with MS] as compared with [healthy controls],” the researchers wrote.
The data “fit well with the growing literature which is emphasizing the predominant role that computerized testing might assume in clinical practice,” they added. “Within this panorama, our videogame distinguishes itself by the fact that patients are tested while basically just playing.”
Researchers noted that the study is limited by its small sample size. They also pointed out that, by design, the video game may not be a useful tool for people whose vision or upper limb mobility is impaired, “thus limiting its applicability to the general MS population.”
“Further research over the videogame’s psychometric characteristics, validity, reliability, and usability needs to be conducted before releasing it into clinical practice,” the researchers wrote.
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