The Symbol Digit Modalities Test (SDMT) is sensitive but non-specific in MS: Lexical access speed, memory, and information processing speed independently contribute to SDMT performance

Sandry, Joshua; Simonet, Daniel; Brandstadter, Rachel; Krieger, Stephen; Sand, Ilana Katz; Graney, Robin; Buchanan, Alexandra V.; Lall, Sophia; Sumowski, James F.

doi:10.1016/j.msard.2021.102950

Cited by 41 publications

(27 citation statements)

References 14 publications

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“…Inasmuch as the drift rate parameter is a measure of processing speed, this leaves a considerable amount of variance unaccounted for. The weak to moderate relationship corroborates other research demonstrating processing speed inferences based exclusively on digit-symbol tests are largely invalid (Jaeger, 2018 ; Joy et al, 2003 ; Mui et al, 2022 ; Sandry et al, 2021 ; Treviño et al, 2021 ) and may more likely reflect multimodal integration (Sandry & Dobryakova, 2021 ). Low specificity does not undermine the value associated with a highly sensitive and quick screener afforded by digit-symbol assessments.…”

Section: Discussionsupporting

confidence: 84%

“…Low specificity does not undermine the value associated with a highly sensitive and quick screener afforded by digit-symbol assessments. This does underscore the importance of follow-up assessment with precision instruments (Sandry et al, 2021 ), of which, response time models may be one viable approach (Mui et al, 2022 ). What will be even more informative is widespread application of computational modelling approaches, including the DDM, to quantify disease-related cognitive changes (Evans & Wagenmakers, 2019 ; Forstmann et al, 2016 ; Ratcliff et al, 2016 ; White et al, 2010 ; Wiecki et al, 2015 ).…”

Section: Discussionmentioning

confidence: 99%

“…However, the psychometric validity of this conclusion is somewhat tenuous. Often, processing speed inferences are based on murky cognitive assessments that tap into much more than “speed” alone (Sandry et al, 2021 ). For example, commonly used digit-symbol coding tests require participants to match symbols in a grid with corresponding digit-symbol pairings in a key in a 90 s time period.…”

Section: Clinical Potential and Limitations Of The Ddmmentioning

confidence: 99%

“…The problem is that, along with a speeded component, these assessments also tap into a wide range of other cognitive processes including learning and memory, language, visual search/attention, etc. (Jaeger, 2018 ; Joy et al, 2003 ; Sandry et al, 2021 ; Treviño et al, 2021 ). In this context, low test scores could reflect changes in cognitive speed, or they may reflect changes in some other cognitive, perceptual or sensorial process.…”

Section: Clinical Potential and Limitations Of The Ddmmentioning

confidence: 99%

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Motor speed does not impact the drift rate: a computational HDDM approach to differentiate cognitive and motor speed

Sandry

Ricker

2022

Cogn. Research

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The drift diffusion model (DDM) is a widely applied computational model of decision making that allows differentiation between latent cognitive and residual processes. One main assumption of the DDM that has undergone little empirical testing is the level of independence between cognitive and motor responses. If true, widespread incorporation of DDM estimation into applied and clinical settings could ease assessment of whether response disruption occurs due to cognitive or motor slowing. Across two experiments, we manipulated response force (motor speed) and set size to evaluate whether drift rates are independent of motor slowing or if motor slowing impacts the drift rate parameter. The hierarchical Bayesian drift diffusion model was used to quantify parameter estimates of drift rate, boundary separation, and non-decision time. Model comparison revealed changes in set size impacted the drift rate while changes in response force did not impact the drift rate, validating independence between drift rates and motor speed. Convergent validity between parameter estimates and traditional assessments of processing speed and motor function were weak or absent. Widespread application, including neurocognitive assessment where confounded changes in cognitive and motor slowing are pervasive, may provide a more process-pure measurement of information processing speed, leading to advanced disease-symptom management.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Clinical Potential and Limitations Of The Ddmmentioning

confidence: 99%

Section: Clinical Potential and Limitations Of The Ddmmentioning

confidence: 99%

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Motor speed does not impact the drift rate: a computational HDDM approach to differentiate cognitive and motor speed

Sandry

Ricker

2022

Cogn. Research

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“… 56–59 In Fabry disease such modular organization is enhanced, and, of note, in our sample was associated with worse working memory. This is not surprising, as we assessed working memory via a digit symbol coding task, that requires the involvement of different neuronal circuits responsible for distinct but partly overlapping cognitive processes (lexical access speed, memory and information processing speed), 60 and would thus likely be affected by the enhanced modular reorganization observed in Fabry disease. In agreement with this interpretation, previous studies have also highlighted a correlation between information processing speed, as measured via digit symbol coding, and WM integrity in Fabry disease, 13 sporadic cerebral small vessel disease, 61–64 and in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).…”

Section: Discussionmentioning

confidence: 99%

Structural disconnection and functional reorganization in Fabry disease: a multimodal MRI study

Gabusi

Pontillo

Petracca

et al. 2022

Brain Communications

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Central Nervous System involvement in Fabry Disease, a rare systemic X-linked lysosomal storage disorder, is characterized by the presence of heterogeneous but consistent functional and microstructural changes. Nevertheless, knowledge about the degree and extension of macro-scale brain connectivity modifications is to date missing. In this work, we performed connectomic analyses of diffusion and resting-state functional MRI to investigate changes of both structural and functional brain organization in Fabry disease, as well as to explore the relationship between the two and their clinical correlates. In this retrospective cross-sectional study, 46 Fabry disease patients (28F, 42.2 ± 13.2years) and 49 healthy controls (21F, 42.3 ± 16.3years) were included. All subjects underwent an MRI examination including anatomical, diffusion and resting-state functional sequences. Images were processed to obtain quantitative structural and functional connectomes, where the connections between regions of interest were weighted by the total intra-axonal signal contribution of the corresponding bundle and by the correlation between blood-oxygen-level dependent timeseries, respectively. We explored between-group differences in terms of both global network properties, expressed with graph measures, and specific connected subnetworks, identified using a network-based statistics approach. As exploratory analyses, we also investigated the possible association between cognitive performance and structural and functional connectome modifications at both global and subnetwork level in a subgroup of patients (n = 11). Compared to healthy controls, Fabry disease patients showed a significantly reduced global efficiency (p = 0.005) and mean strength (p < 0.001) in structural connectomes, together with an increased modularity (p = 0.005) in functional networks. As for the network-based statistics analysis, a subnetwork with decreased structural connectivity in Fabry disease patients compared to healthy controls emerged, with 8 nodes mainly located at the level of frontal or deep grey matter areas. When probing the relation between altered global network metrics and neuropsychological tests, correlations emerged between the structural and functional disruption with results at verbal and working memory tests, respectively. Furthermore, structural disruption at subnetwork level was associated with worse executive functioning, with a significant moderation effect of functional changes suggesting a compensation mechanism. Taken together, these results further expand the current knowledge about brain involvement in Fabry disease, showing widespread structural disconnection and functional reorganization, primarily sustained by loss in axonal integrity and correlating with cognitive performance.

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Impact of Acute Dopamine Replacement on Cognitive Function in Parkinson's Disease

Seemiller,

Morrow,

Hinkle

et al. 2024

Movement Disord Clin Pract

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BackgroundPD causes striatal dopaminergic denervation in a posterior/dorsal to anterior/ventral gradient, leaving motor and associative cortico‐striato‐pallido‐thalamic loops differentially susceptible to hyperdopaminergic effects with treatment. As the choice and titration of symptomatic PD medications are guided primarily by motor symptoms, it is important to understand their cognitive implications.ObjectiveTo investigate the effects of acute dopaminergic medication administration on executive function in Parkinson's disease (PD).MethodsParticipants with idiopathic PD were administered the oral Symbol Digit Modalities Test (SDMT; n = 181) and the Stroop test (n = 172) in the off‐medication and “best on” medication states. ANCOVA was used to test for differences between off‐medication and on‐medication scores corrected for age and years of education.ResultsAfter administration of symptomatic medications, scores worsened on the SDMT (F = 11.70, P < 0.001, d = −0.13), improved on the Stroop color (F = 26.89, P < 0.001, d = 0.184), word (F = 6.25, P = 0.013, d = 0.09), and color‐word (F = 13.22, P < 0.001, d = 0.16) test components, and the Stroop difference and ratio‐based interference scores did not significantly change. Longer disease duration correlated with lower scores on the SDMT, Stroop color, word, and color‐word scores; however, longer disease duration and higher levodopa‐equivalents correlated with higher Stroop difference‐based interference scores.ConclusionsSymptomatic medication differentially affects performance on two cognitive tests in PD. After acute treatment, core Stroop measures improved, Stroop interference was unchanged, and SDMT performance worsened, likely reflecting complex changes in processing speed and executive function related to acute treatment. When considering motor symptom therapies in PD, an individual's cognitive demands and expectations, especially regarding executive function, should be considered.

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The Symbol Digit Modalities Test (SDMT) is sensitive but non-specific in MS: Lexical access speed, memory, and information processing speed independently contribute to SDMT performance

Cited by 41 publications

References 14 publications

Motor speed does not impact the drift rate: a computational HDDM approach to differentiate cognitive and motor speed

Motor speed does not impact the drift rate: a computational HDDM approach to differentiate cognitive and motor speed

Structural disconnection and functional reorganization in Fabry disease: a multimodal MRI study

Impact of Acute Dopamine Replacement on Cognitive Function in Parkinson's Disease

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