Deficits in Planning Time but not Performance in Patients with Multiple Sclerosis

Abstract

Studies of planning ability typically involve some version of the Tower of Hanoi or Tower of London (TOL). When these tests are administered to patients with multiple sclerosis (MS), the findings pertaining to planning "performance" have been conflicting. Possible reasons for failures to find deficits in planning performance among MS patients are: (a) the patients typically have relapsing-remitting MS (RRMS) of mild severity and short duration and thus little cognitive impairment relative to those with more advanced disease; (b) the problems composing the tests are too simple and differences between patients and controls are therefore obscured by ceiling effects; and (c) the scoring system typically used permits participants to earn points for successful solutions on later trials after failing the initial attempt on each problem, thereby further diluting the difference between patients and controls. The present study compared the performance of patients with both relapsing-remitting and secondary progressive disease with that of healthy controls on a more challenging version of the TOL. Patients exhibited lengthier planning times on the test, greater disparity in their average planning times from those of controls as the difficulty level increased, and greater individual variability in their planning times across the full set of problems. However, no differences in planning performance were found between patients and controls or between RRMS and secondary progressive MS patients. Performance differences in other studies may be attributable in part to the imposition of time limits for solving each problem and the disproportionately adverse effect such time limits have on patients' performance.

Difficulties in Planning Among Patients with Multiple Sclerosis: A Relative Consequence of Deficits in Information Processing Speed

“…As in previous studies, however, patients exhibited slower planning times than controls, with the disparity again increasing with problem difficulty (Denney et al, 2012).…”

“…Lower point scores for MS patients have been reported by several investigators (Arnett et al, 1997; Correspondence and reprint requests to: Douglas R. Denney, Department of Psychology, 1415 Jayhawk Blvd., Lawrence, KS 66045-7556. E-mail: denney@ku.edu Foong et al, 1997Foong et al, , 1999Lazeron, Rombouts, Scheltens, Polman, & Barkhof, 2004), but all of our studies (Denney et al, 2004(Denney et al, , 2005(Denney et al, , 2008(Denney et al, , 2012 have failed to show a difference in the point scores of MS patients and controls. Furthermore, Drew et al (2008) found that the mean point score for a large sample of MS patients on the Tower Test of the Delis-Kaplan Executive Function System (Delis, Kaplan, & Kramer, 2001) was equal to that of the sample on which the test was normed.…”

“…The untimed condition conformed to the usual way in which the TOL has been administered in all of our prior studies (Denney et al, 2004(Denney et al, , 2005(Denney et al, , 2008(Denney et al, , 2012. No restriction was placed on the amount of time the participant was allowed to solve each problem.…”

“…These limits were based on an analysis of the solution times from a previous study of MS patients involving the same ''untimed,'' 16-item version of the TOL (Denney et al, 2012). At the beginning of the task, participants in the timed condition were told, ''The time limits are based on an average solution time from a previous study; working within the time limit should be challenging, but not impossible.…”

“…Throughout the MS literature, there is good agreement with respect to planning time. All studies that have included this measure report slower planning times for MS patients than controls (Arnett et al, 1997;Denney, Gallagher, & Lynch, 2011;Denney, Hughes, Owens, & Lynch, 2012;Denney, Lynch, & Parmenter, 2008;Denney, Lynch, Parmenter, & Horne, 2004;Denney, Sworowki, & Lynch, 2005;Foong et al, 1997), and in some of these studies (Denney et al, 2004(Denney et al, , 2012, the disparity in planning times for patients and controls tends to become greater as the problems increase in difficulty.…”