Multiple Sclerosis Fatigue: A Longitudinal Structural MRI and Diffusion Tensor Imaging Study.

BACKGROUND AND PURPOSE: Previous cross-sectional studies have reported the involvement of thalamus, pallidum, superior cerebellar peduncle, temporal cortex, and fronto-parietal white matter in multiple sclerosis (MS)-related fatigue. However, the longitudinal imaging correlates of fatigue severity variation in MS remain unclear. METHODS: Structural and diffusion tensor imaging (DTI) data were collected from 43 relapsing remitting MS (RRMS) patients with fatigue (Fatigue Severity Scale [FSS] range: 1-7). Subcortical nuclei volume using FreeSurfer and cortical diffusion indices using a cross-modality technique were measured at baseline and year 1. RESULTS: The pallidal volume had significantly decreased (P = .002) by year 1, although the fatigue score variation was not significant. At year 1, the pallidal volume (P = .023) and fractional anisotropy (FA, P = .013) of right temporal cortex (RTC) correlated significantly with FSS. CONCLUSIONS: The pallidal volume and the FA-RTC may be used to evaluate longitudinal fatigue severity variation. Our study proposes new biomarkers to monitor fatigue severity in MS patients.

Lipid accumulation product and metabolic syndrome: a population-based study in northern Iran, Amol.

PURPOSE: Lipid accumulation product (LAP) demonstrated a strong predictive accuracy for metabolic syndrome (MetS) in previous studies. This study was conducted to determine the predictive performance of LAP compared to obesity indexes. Moreover, the optimal cutoff point of LAP based on the study population waist circumference threshold was estimated in both men and women. METHODS: 5797 subjects with an average age of 44.77 ± 16.77 years for men and 43.78 ± 15.43 years for women were included in the present study. The ROC analysis was performed to assess the predictive accuracy of LAP in the diagnosis of MetS. The optimal cutoff point of LAP was determined according to maximal Youden index in both men and women. RESULTS: The optimal cutoff points determined for LAP were 49.71 (sensitivity = 85.2 %, specificity = 82.3 %) for women and 39.89 (sensitivity = 86 %, specificity = 79.6 %) for men. Based on the assigned cutoff points, the prevalence of high LAP was obtained 44.1 % in men and 45.1 % in women. LAP also showed a significantly higher predictive performance for MetS compared to obesity measures and also TG. CONCLUSION: LAP has a strong and reliable diagnostic accuracy for MetS in Iranian population in the north of Iran. LAP showed a better predictability than other obesity indexes assessed in the present study.

Mental workload in heat: toward a framework for analyses of stress states.

BACKGROUND: Effects of stress on performance are often interpreted by recourse to the arousal theory, which accounts for performance effects only in relation to the level of nervous system activity. This omits voluntary control that may be exerted in moderating stress effects. The present work elaborates on two control processes (viz., strategies and effort exertion) from the standpoint of the theory of mental workload, which was assessed in two experiments as a function of task demand and heat stress. Task demand was varied by increasing the complexity of decision rules and by presenting feedback indicating efficiency of task-strategies. HYPOTHESES: As decision rules are made more complex, task demand increases, causing longer reaction time (RT) and higher workload. Feedback improves performance by affecting strategies and effort exertion. Heat's effect on performance is related to the generated thermophysiological state and degree of effort exerted to maintain efficiency. METHOD: Performance and workload were measured in a decision-making task as a function of complexity of decision rules and feedback in 22 degrees C and 40 degrees C temperature conditions. Workload was measured by secondary task RT (STRT), subjective rating of effort (SRE), and heart rate (HR). Core temperature (Tc) was monitored continuously. RESULTS: Primary task RT (PTRT), STRT, SRE, and HR increased as complexity of decision rules increased. Feedback decreased PTRT, and increased STRT, SRE, and HR. In heat, a higher Tc was associated with a shorter PTRT and a longer STRT. CONCLUSIONS: A substantial part of variation in adaptation to demand was accounted for by control processes that involved higher cognitive functions.

Sustained attention and serial responding in heat: mental effort in the control of performance.

The effects of heat (40 degrees C) on sustained attention and serial responding were studied in a simple reaction time task and a serial four choice reaction time task, respectively. Core temperature (Tc), heart rate variability (HV) and subjective reactions were monitored during the 80 min of exposure time. Simple reaction time performance and accuracy in the serial choice reaction time task deteriorated significantly in heat. In the serial choice reaction time task, the effects of heat on response times and on HV were correlated. Performance and level of Tc were not correlated, but a relationship was found between performance and rate of Tc change. Results are discussed in relation to the thermophysiological status of the subjects and the compensatory mechanism of effort allocation. It is proposed that task characteristics regulate the degree of activity of this compensatory mechanism.