RESUMO
Background: Fifty-one percent of individuals with multiple sclerosis (MS) develop cognitive impairment (CI) in information processing speed (IPS). Although IPS scores are associated with health and well-being, neural changes that underlie IPS impairments in MS are not understood. Resting state fMRI can provide insight into brain function changes underlying impairment in persons with MS. Objectives: We aimed to assess functional connectivity (FC) differences in (i) persons with MS compared to healthy controls (HC), (ii) persons with both MS and CI (MS-CI) compared to HC, (iii) persons with MS that are cognitively preserved (MS-CP) compared to HC, (iv) MS-CI compared to MS-CP, and (v) in relation to cognition within the MS group. Methods: We included 107 participants with MS (age 49.5 ± 12.9, 82% women), and 94 controls (age 37.9 ± 15.4, 66% women). Each participant was administered the Symbol Digit Modalities Test (SDMT) and underwent a resting state fMRI scan. The MS-CI group was created by applying a z-score cut-off of ≤-1.5 to locally normalized SDMT scores. The MS-CP group was created by applying a z-score of ≥0. Control groups (HCMS-CI and HCMS-CP) were based on the nearest age-matched HC participants. A whole-brain ROI-to-ROI analysis was performed followed by specific contrasts and a regression analysis. Results: Individuals with MS showed FC differences compared to HC that involved the cerebellum, visual and language-associated brain regions, and the thalamus, hippocampus, and basal ganglia. The MS-CI showed FC differences compared to HCMS-CI that involved the cerebellum, visual and language-associated areas, thalamus, and caudate. SDMT scores were correlated with FC between the cerebellum and lateral occipital cortex in MS. No differences were observed between the MS-CP and HCMS-CP or MS-CI and MS-CP groups. Conclusion: Our findings emphasize FC changes of cerebellar, visual, and language-associated areas in persons with MS. These differences were apparent for (i) all MS participants compared to HC, (ii) MS-CI subgroup and their matched controls, and (iii) the association between FC and SDMT scores within the MS group. Our findings strongly suggest that future work that examines the associations between FC and IPS impairments in MS should focus on the involvement of these regions.
RESUMO
The anaerobic lactate threshold (LTan) is used to prescribe training intensity and measure endurance capacity. The LTan identifies a critical point where small increases in workload result in large increases in blood lactate concentration. LTan is usually predicted through visual inspection of a blood lactate (bLa) vs workload plot. Numerous other methods for predicting LTan exist, and the literature lacks a consensus regarding validity of prediction methods. The purpose of this study was to assess the agreement among visual inspection (VI), maximum distance (Dmax) and modified maximum distance (Dmod) from the lactate curve, Baldari & Guidetti (BG), Dickhuth & Heck (DH) and Keul (K) methods for predicting the LTan. Blood lactate data was gathered from 8 male elite cross country skiers across two treadmill running incremental exercise tests. The above methods were used to predict LTan. Bland-Altman limits of agreement and Lin's Concordance Correlation Coefficient analyses were used to compare methods. Agreement was defined as 95% limits of agreement falling within a maximum allowed difference of ± 0.5 mM bLa between methods. No agreement was found among any of the prediction methods. Mean LTan calculated with the Dmax method was significantly different (p < 0.05) from mean LTan calculated using each other method. We conclude that the six methods for predicting LTan used in this study are not in agreement and should not be considered equivalent for exercise testing purposes. Future studies should compare agreement between LTan methods and the maximal lactate steady state to determine the most valid LTan prediction method.