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The Impact of a Sustained Cognitive Engagement Intervention on Cognitive Variability: the Synapse Project

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Interest in maintaining one’s cognitive ability and quality of life through older adulthood has greatly increased in recent years. However, research examining the effectiveness of cognitive engagement interventions on older adults is mixed and the mechanisms behind improving cognition in older age are unknown. It is possible that traditional measures of cognitive outcomes, such as average reaction time, may overlook potential benefits due to a lack of sensitivity in these measures. One alternative metric is intraindividual variability (IIV) in response speed (short-term variations in performance on reaction time tasks), which reflects fluctuations in attention and is a sensitive behavioral measure of neurological integrity that is predictive of future cognitive decline and impairment. The current study aimed to investigate whether IIV was improved in older adults through productive cognitive engagement (i.e., acquisition of new skills) in comparison with receptive engagement (activities that rely upon existing knowledge). Participants were 173 typically aging adults aged 60–90 years who were recruited to the Synapse Project and randomly allocated to a productive engagement activity (learning to quilt and/or conduct digital photography) or receptive engagement activity (socializing, or placebo cognitive tasks such as completing crosswords). Participants completed three flanker tasks at baseline and after completing the 14-week intervention program. IIV was calculated as the trial-to-trial variability in responding to congruent and incongruent trials in each task. Neither traditional intent-to-treat nor complier average causal effect modeling analyses showed any significant improvements in IIV for either intervention group. Further, Bayesian analyses showed that there was moderate evidence in favor of the null hypothesis. An intensive cognitive activity intervention did not result in a reduction in IIV. We suggest that intervention programs may need to specifically engage cognitive domains associated with IIV (i.e., attention, executive control) for improvements to be observed. Additionally, other design factors such as using a longer duration and/or applying the intervention to atypically aging groups, such as those with mild cognitive impairment, may increase the likelihood of significantly reducing IIV via an intervention.

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The authors would like to thank Denise Park for kindly sharing her data for analysis in this study, and for her feedback on a previous version of the manuscript.


Research reported in this publication was financially supported by the National Institute on Aging of the National Institutes of Health under award number R03AG055748 to A. A. M. Bielak. The Synapse Project was funded by the National Institute of the National Institutes of Health 5R01AG026589 and a supplement from the American Recovery and Reinvestment Act 3R01AG026589-03S1, both awarded to D. C. Park.

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CRB: Contributed to the analysis and interpretation of data, and the writing and editing of the manuscript. AAMB: Contributed to the design of the work, acquisition and interpretation of data, and editing of the manuscript. All authors approved the submitted version of the manuscript.

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Correspondence to Christopher R. Brydges.

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As the current study is a secondary analysis on previously published data, our institution’s research ethics committee declared these analyses exempt.

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The authors declare that they have no conflicts of interest.


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Brydges, C.R., Bielak, A.A.M. The Impact of a Sustained Cognitive Engagement Intervention on Cognitive Variability: the Synapse Project. J Cogn Enhanc 3, 365–375 (2019).

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