Contributions
Abstract: P1113
Type: Poster
Abstract Category: Pathology and pathogenesis of MS - Neuropsychology
Background: Information processing speed is a hallmark cognitive deficit in multiple sclerosis (MS). The Symbol Digit Modalities Test (SDMT) is considered the most sensitive indicator of processing speed.
Objective: To modify the SDMT by reducing the working memory component and focusing primarily on processing speed.
Methods: Two computerized versions of the SDMT (c-SDMT) were developed. In the fixed version the symbol-digit key is kept constant throughout the 8 trials of the test, whereas in the variable version a different key is presented for each trial. Each trial consisted of 9 symbols and digits. A total sample of 78 MS and 68 healthy control (HC) subjects, matched in age, gender, years of education and premorbid IQ, were recruited. Forty MS and 33 HC subjects were administered the fixed c-SDMT, and 38 MS and 35 HC subjects the variable version.
Results: MS subjects performed significantly slower than HC subjects on both the fixed (mean [SD]: 15.19 [5.61] vs. 12.14 [1.73] seconds, t=-2.997, p=0.004) and variable (15.11 [3.48] vs. 13.08 [2.26] seconds, t=-2.967, p=0.004) c-SDMT respectively. There were no differences in mean time between the fixed and variable tests for MS and HC subjects (t=0.078, p=0.938 and t=-1.907, p=0.061 respectively). While the HC group demonstrated changes over time in performance speed on both the fixed (repeated measures ANOVA, F=12.281, p< 0.001) and variable (F=4.161, p=0.001) c-SDMT, the MS group did so only on the former (F=13.812, p< 0.001).
Conclusions: MS subjects no longer show an improvement in serial performance on the SDMT when the working memory component is substantially reduced. This suggests that purer measures of processing speed may be relatively resistant to practice effects in people with MS.
Disclosure: This study was funded by the Multiple Sclerosis Society of Canada
Viral Patel: nothing to disclose
Lisa Walker: nothing to disclose
Anthony Feinstein: Dr. Anthony Feinstein has received speaker honoraria from Merck Serono, Teva Pharmaceuticals Industries Ltd., Novartis, and Biogen Idec; serves on the editorial boards of Multiple Sclerosis Journal; receives publishing royalties for The Clinical Neuropsychiatry of Multiple Sclerosis (Cambridge University Press, 2007); chairs the Medical Advisory Committee for the Multiple Sclerosis Society of Canada; conducts neuropsychiatric evaluation, cognitive testing, and brain imaging in neuropsychiatry in his clinical practice; and receives research support from the Canadian Institute of Health Research and the Multiple Sclerosis Society of Canada.
Abstract: P1113
Type: Poster
Abstract Category: Pathology and pathogenesis of MS - Neuropsychology
Background: Information processing speed is a hallmark cognitive deficit in multiple sclerosis (MS). The Symbol Digit Modalities Test (SDMT) is considered the most sensitive indicator of processing speed.
Objective: To modify the SDMT by reducing the working memory component and focusing primarily on processing speed.
Methods: Two computerized versions of the SDMT (c-SDMT) were developed. In the fixed version the symbol-digit key is kept constant throughout the 8 trials of the test, whereas in the variable version a different key is presented for each trial. Each trial consisted of 9 symbols and digits. A total sample of 78 MS and 68 healthy control (HC) subjects, matched in age, gender, years of education and premorbid IQ, were recruited. Forty MS and 33 HC subjects were administered the fixed c-SDMT, and 38 MS and 35 HC subjects the variable version.
Results: MS subjects performed significantly slower than HC subjects on both the fixed (mean [SD]: 15.19 [5.61] vs. 12.14 [1.73] seconds, t=-2.997, p=0.004) and variable (15.11 [3.48] vs. 13.08 [2.26] seconds, t=-2.967, p=0.004) c-SDMT respectively. There were no differences in mean time between the fixed and variable tests for MS and HC subjects (t=0.078, p=0.938 and t=-1.907, p=0.061 respectively). While the HC group demonstrated changes over time in performance speed on both the fixed (repeated measures ANOVA, F=12.281, p< 0.001) and variable (F=4.161, p=0.001) c-SDMT, the MS group did so only on the former (F=13.812, p< 0.001).
Conclusions: MS subjects no longer show an improvement in serial performance on the SDMT when the working memory component is substantially reduced. This suggests that purer measures of processing speed may be relatively resistant to practice effects in people with MS.
Disclosure: This study was funded by the Multiple Sclerosis Society of Canada
Viral Patel: nothing to disclose
Lisa Walker: nothing to disclose
Anthony Feinstein: Dr. Anthony Feinstein has received speaker honoraria from Merck Serono, Teva Pharmaceuticals Industries Ltd., Novartis, and Biogen Idec; serves on the editorial boards of Multiple Sclerosis Journal; receives publishing royalties for The Clinical Neuropsychiatry of Multiple Sclerosis (Cambridge University Press, 2007); chairs the Medical Advisory Committee for the Multiple Sclerosis Society of Canada; conducts neuropsychiatric evaluation, cognitive testing, and brain imaging in neuropsychiatry in his clinical practice; and receives research support from the Canadian Institute of Health Research and the Multiple Sclerosis Society of Canada.