Multiple Sclerosis and Speed of Information Processing

Cleota J. Lock
Missouri Western State College
May 1, 1997

Abstract

MS is a chronic multifocal demyelinating disease of the central nervous system in which myelin and oliogodendrozypes are selectively destroyed by immunal competent cells. Neuropsychological studies have evaluated some specific intellectual abilities in people with MS, these are: memory, speed of information processing, verbal fluency, conceptual/abstract reasoning, and visuospacial information processing. Cognitive impairment can complicate the persons life as a lack of understanding from others and the inability to communicate efficiently with friends, family, co-workers and employers takes its toll on the person. The participants consisted of two groups of five people each. A timed word test was administered, and the responses were measured with the variables of words starting with the letter ÒAÓ, and the letter ÒSÓ, as well as with the variable of mammals. I conducted a two-way independent t test on each variable, the results of which were not significant. The majority of this research indicates that MS is often accompanied with a slower speed of information processing. While there were indicators that did point to MS people having slower information processing, the results were not significant, because of an inability to acquire enough participants for the MS group. Further research would benefit from the use of a larger sample size.

Introduction

It has been a long known fact that people with multiple sclerosis (MS) have been observed to have different degrees of cognitive impairment. Past research implies that only those severely afflicted would have any appreciable impairment, but more recent research points to a substantial number of patients in relatively mild or early stages. In fact, for some patients a predominant complaint is that of difficulty in memory and concentration that is severe enough to interfere with daily functioning (Ryan, 1996).

MS is a chronic multifocal demyelinating disease of the central nervous system in which myelin and oliogodendrozypes are selectively destroyed by immunal competent cells. It has been estimated that 50% of MS patients have some degree of cognitive impairment. There are approximately 250,000 to 350,000 physician diagnosed cases, and up to 175,00 of these are thought to have some cognitive impairment. Cognitive impairment can complicate the persons life as a lack of understanding from others and the ability to communicate efficiently with friends, family, co-workers and employers takes its toll on the person (Foley, et al., 1994).

Neuropsychological studies have evaluated some specific intellectual abilities in people with MS, these are: memory, speed of information processing, verbal fluency, conceptual/abstract reasoning, and visuospacial information processing. While the effects on the retrieval of long-term memory has been cited as the most common finding in MS, some investigators have also found deficits in short-term memory (Foley, et al., 1994). Compared to controls, persons with MS are more likely to experience difficulty in shifting cognitive sets, in forming abstract concepts, and in visual analogic reasoning. Many patients report that word findings and memory problems impair their ability to communicate with others. Thus, there is a great need to develop programs to assist cognitively impaired persons with MS with improving communication skills.

A number of different investigators have found a link that supports the hypothesis that differences in speed of information processing may also be connected to individual differences in I.Q. Further studies have shown that speed of processing has been directly linked to central nervous system functioning and I. Q. (Bee, 1997). It is now possible to measure the speed of conduction of impulses along individual nerves, such as the nerves in the arm.

It has been found that tests of attention require rapid responding place at the very least minimal demands on immediate memory. Many of these tests require manual or written responses. When these responses are required and response speed is the measure of performance, nearly all MS patients exhibit some impairment. However, the use of vocal responses and measures of accuracy, as opposed to speed, help to overcome these problems. The literature is consistent, most MS patients are impaired on a variety of measures of visual or auditory abilities(Beatty & Scott, 1993).

Studies using the Sternberg Memory Scanning Test provide the most direct evidence for slowed information processing speed in individuals with MS. Since reaction time increases linearly with the number of items in the set, the slope of the function relating reaction time to set size provides a measure of memory scanning speed. In two studies, Rao and colleagues have observed increase in slope as well as intercept for MS patients. The patients require 20 to 30 msec. longer than controls to process each additional digit. In a selective reminding test which separates recall of information from primary and secondary memory Rao, et al. (1992), found evidence that primary memory remains essentially intact in MS.

Another selective reminding test by Buschke (1973) provided evidence for the retrieval of information failure. It was also reported that compared to age and education equated normal controls, MS patients recall fewer total words during acquisition on a SRT test and after a one hour delay.

The hypothesis that memory impairments in MS are secondary to acquisition, parallels the view that MS patients acquire information more slowly than normal but, that once acquired, memory is normal (Beatty & Wilbanks, 1996). Although studies have attempted to determine whether there are particular clinical factors that influence the presence and nature of the cognitive difficulties in MS, they have not shown a statistically significant association. Some weak correlations have been found between disease duration and memory difficulty. Fatigue has recently been considered to be a prominent complaint of MS patients. While this finding was not significant on reaction time performance, it was however observed that fatigue was associated with slowed reaction time on the motor component of memory tasks (Grossman, et al., 1994).

Some cognitive factors that may be related to impairment of working memory are a significant correlation in MS patients between dual-task performance and the PASAT. Performance on this measures relies heavily on speed of information processing. Other studies of MS patients have also documented this fact. This also suggests that impaired cognitive processing may contribute to poor performance under dual-task conditions. A recent study has also postulated that working memory impairments may be due to impairments in the speed and capacity of central information processing. These findings provide converging evidence to support the observation of a relationship between impaired working memory and information processing speed in MS patients (DÕEsposito, et al., 1996).

I would like to be able to link the results of my study to the daily functioning needs of people with MS. I think that is hard for much of the general public to fully understand the diversity of this disease. Cognitive impairment is not always associated with physical impairment, and therefore may not be as easily recognized or accepted. In my research I found that cognitive disturbances have a negative influence on the occupational opportunities of individuals with MS. Therefore, my goal is to help generate a greater awareness concerning the individual needs of MS patients, and to encourage the development of programs that would provide training and rehabilitation to address these needs.

Methods

Subjects

The participants consisted of two groups of five people each. In the first I asked for volunteers from the MS Society, and for a comparison I asked for volunteers with similar characteristics from individuals from the Missouri Western State College.

Materials

A timed word test was used that consisted of three parts; the first was to list all the words that they could think of beginning with the letter ÒAÓ, including proper nouns, the second was to list words that started with the letter ÒSÓ, and the third was to list all the mammals that they could recall. Additionally a list of six numbers was given, along with a set of simple math computations.

Procedure

To begin with each participant was given a list of six numbers which could not be written down. Next instructions were given for completing the three part word test, with each part being timed for one minute. The first part asked participants to write down as many words that started with the letter ÒAÓ, including proper names. Then instructions were given to write down as beginning with the letter ÒSÓ that they could think of. To complete the word portion of the test, each participant was instructed to list as many mammals as they could recall. Following this word test, they were asked to complete as many math problems as they could in one minute. Finally the participants were asked to recall as many of the six numbers as possible from the original list.

Results

I conducted a two-way independent t-test on the variable of words that begin with the letter ÒAÓ. The mean for group one (MS group) was 12, and for group two (control) was 16. Results were t (6) = -2.09, p =.082, which was a non-significant trend in the expected direction.

Next I conducted a two-way independent t-test on the variable of mammals. The mean for group one was 13.75, and for group two was 15.25. Results were t (6) = -.38, p & GT .05, which was not significant.

I then conducted a two-way independent t-test on the variable of memory. The mean for group one was 4.5, and for group two was 5.25. Results were t (6) =-1.34, p & GT .05, which was again not significant.

Finally, I conducted a two-way independent t-test on the variable of words that begin with the letter ÒSÓ. The mean for group one was 14.5, and for group two was 18.75. Results were t (6) =-1.59, p & GT .05, which was not significant as well.

Discussion

MS is a highly diverse disease, which spans a wide scale of disability. One disability that is not visible is the problems that a great number of MS people experience in the speed of information processing. Numerous tests have been conducted in this area of MS and speed of information processing. The majority of this research indicates that MS is often accompanied with a slower speed of information processing. It was the intention of this study to conduct an experiment which would also show that a significant difference exists between normal controls and those with MS. While the results failed to show a significant difference, it is my belief that this is due to the limited sample size. While there were indicators that did point to MS people having slower information processing, the statistics were not significant, because of an inability to acquire enough participants for the MS group. Further research would benefit from the use of a larger sample size.

References

Beatty, W.W., & Scott, J.G., 1993. Issues and developments in the neuropsychological assessment of patients with multiple sclerosis. Journal of Neurologic Rehabilitation, 7, 87-97.

Beatty, W.W., Blanco,C.R.., Wilbanks, Sl., Paul, R.H., & Hames, K.A.1995. Demographic , clinical, and cognitive characteristics of multiple sclerosis patients who continue to work. Journal of Neurologic Rehabilitation. 9, 167-173.

Beatty,W.W., Wilbanks, S. L. Blanco, C.R., Hames, K.A., Tivis, R.., & Paul, R. H., 1996. Memory disturbance in multiple sclerosis: Reconsideration of patterns of performance on the selective reminding test. Journal Of Clinical and Experimental Neuropsychology, 18, 56-62.

DÕEsposito, M., Onishi, K., Thompson, H., Robinson, K., Armstrong, A., & Grossman, M., 1996. Working memory impairments in multiple sclerosis: Evidence from dual-task paradigm. Neuropsychology, 10, 51-56.

Foley, F.W., Dince. W.M.., Bedell, J. R., LaRocca, N. G., Kalb. R. Caruso, L.S. Smith, C.R., & Shnek, Z.M., 1994. Psychoremediation of communication skills for cognitively impaired persons with multiple sclerosis. Journal Neurological Rehabilitation, 8, 165-176.

Grossman, M. Armstrong, & Kolson, D. 1994. Neuropsychiatry, Neuropsychology, and Behavioral Neurology, 7, 194-210.

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