Highlights
- •Intra-individual variability (IIV) in reaction times from computerized psychomotor tasks may mark early cognitive decline
- •The commercial testing platform Cogstate offers standardized psychomotor task administration and provides measures of IIV
- •We found that Cogstate IIV value is consistent with alternative and experimental approaches to calculating IIV
- •The Cogstate platform provides an IIV value for clinical research and normative comparison for clinical use
Abstract
Objectives
Intra-individual variability (IIV), measured across repeated response times (RT) during
continuous psychomotor tasks, is an early marker of cognitive change in the context
of neurodegeneration. To advance IIV towards broader application in clinical research,
we evaluated IIV from a commercial cognitive testing platform and compared it to the
calculation approaches used in experimental cognitive studies.
Methods
Cognitive assessment was administered in participants with multiple sclerosis (MS)
during the baseline of an unrelated study. Cogstate was used for computer-based measures
providing three timed-trial tasks measuring simple (Detection; DET) and choice (Identification;
IDN) RT and working memory (One-Back; ONB). IIV for each task was automatically output
by the program (calculated as a log10-transformed standard deviation or “LSD”). We calculated IIV from the raw RTs using
coefficient of variation (CoV), regression-based, and ex-Gaussian methods. The IIV
from each calculation was then compared by rank across participants.
Results
A total of n = 120 participants with MS aged 20–72 (Mean ± SD, 48.99 ± 12.09) completed the baseline
cognitive measures. For each task, the interclass correlation coefficient was generated.
Each ICC showed that LSD, CoV, ex-Gaussian, and regression methods clustered strongly
(Average ICC for DET: 0.95 with 95% CI [0.93, 0.96]; Average ICC for IDN: 0.92 with
95% CI [0.88 to 0.93]; Average ICC for ONB: 0.93 with 95% CI [0.90 to 0.94]). Correlational
analyses indicated the strongest correlation between LSD and CoV for all tasks (rs ≥ 0.94).
Conclusion
The LSD was consistent with research-based methods for IIV calculations. These findings
support the use of LSD for the future measurement of IIV for clinical studies.
Keywords
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Article info
Publication history
Published online: February 12, 2023
Accepted:
February 9,
2023
Received in revised form:
December 29,
2022
Received:
October 26,
2022
Identification
Copyright
© 2023 Published by Elsevier B.V.
