Sleep disturbance and deficits of sustained attention following stroke

Objective: To simultaneously investigate the prevalence of and impact that the poststroke complications of daytime sleepiness, poor sleep quality, depression, and fatigue may be having upon deficits of sustained attention, as assessed using the Psychomotor Vigilance Task (PVT). Method: Twenty-two patients with stroke (mean age: 68.23 ± 12.17 years) and 20 healthy control participants (mean age: 68.1 ± 9.5 years) completed subjective measures of daytime sleepiness, sleep quality, fatigue, and depression and an objective measure of sustained attention as assessed using the PVT. Results: Patients with stroke compared to controls showed heightened levels of fatigue (p = .001, η² = .29) and depression (p = .002, η² = .23), plus greater deficits of sustained attention as reflected by poorer performance across all PVT outcome measures including: slower mean reaction times (p = .002, η² = .22); increased number of lapses (p = .002, η² = .24); and greater variability in reaction time (RT) responses (p = .016, η² = .15). Reaction time distribution analysis suggested that daytime sleepiness and sleep quality had little influence across PVT performance; however, depressive symptomology was associated with longer RT responses, indicative of inattention, and fatigue impacted upon the entire distribution of PVT responses. Conclusions: PVT performance illustrated significant deficits across the domain of sustained attention for patients with stroke in comparison to healthy controls, in terms of inattention as well as slower sensory–motor speed. The common poststroke complications of depressive symptomology and fatigue appear to be associated with these deficits in sustained attention, warranting further investigation.     

Parkinson’s disease and the Stroop color word test: processing speed and interference algorithms

Objective: Processing speed alters the traditional Stroop calculations of interference. Consequently, alternative algorithms for calculating Stroop interference have been introduced to control for processing speed, and have done so in a multiple sclerosis sample. This study examined how these processing speed correction algorithms change interference scores for individuals with idiopathic Parkinson’s disease (PD, n = 58) and non-PD peers (n = 68). Method: Linear regressions controlling for demographics predicted group (PD vs. non-PD) differences for Jensen’s, Golden’s, relative, ratio, and residualized interference scores. To examine convergent and divergent validity, interference scores were correlated with standardized measures of processing speed and executive function. Results: PD–non-PD differences were found for Jensen’s interference score, but not Golden’s score, or the relative, ratio, and residualized interference scores. Jensen’s score correlated significantly with standardized processing speed but not executive function measures. Relative, ratio, and residualized scores correlated with executive function but not processing speed measures. Golden’s score did not correlate with any other standardized measures. Conclusions: The relative, ratio, and residualized scores were comparable for measuring Stroop interference in processing speed-impaired populations. Overall, the ratio interference score may be the most useful calculation method to control for processing speed in this population.     

How strong is the relationship between glaucoma,the retinal nerve fibre layer,and neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis?

Glaucoma is a neurodegenerative disorder with established relationships with ocular structures such as the retinal nerve fibre layer (RNFL) and the ganglion cell layer (GCL). Ocular imaging techniques such as optical coherence tomography (OCT) allow for quantitative measurement of these structures. OCT has been used in the monitoring of glaucoma, as well as investigating other neurodegenerative conditions such as Alzheimer''s disease (AD) and multiple sclerosis (MS). In this review, we highlight the association between these disorders and ocular structures (RNFL and GCL), examining their usefulness as biomarkers of neurodegeneration. The average RNFL thickness loss in patients with AD is 11 μm, and 7 μm in MS patients. Most of the studies investigating these changes are cross-sectional. Further longitudinal studies are required to assess sensitivity and specificity of these potential ocular biomarkers to neurodegenerative disease progression.     

In vivo quantification of hyperoxic arterial blood water T1

Normocapnic hyperoxic and hypercapnic hyperoxic gas challenges are increasingly being used in cerebrovascular reactivity (CVR) and calibrated functional MRI experiments. The longitudinal arterial blood water relaxation time (T_1a) change with hyperoxia will influence signal quantification through mechanisms relating to elevated partial pressure of plasma‐dissolved O₂ (pO₂) and increased oxygen bound to hemoglobin in arteries (Y_a) and veins (Y_v). The dependence of T_1a on Y_a and Y_v has been elegantly characterized ex vivo; however, the combined influence of pO₂, Y_a and Y_v on T_1a in vivo under normal ventilation has not been reported. Here, T_1a is calculated during hyperoxia in vivo by a heuristic approach that evaluates T₁‐dependent arterial spin labeling (ASL) signal changes to varying gas stimuli. Healthy volunteers (n = 14; age, 31.5 ± 7.2 years) were scanned using pseudo‐continuous ASL in combination with room air (RA; 21% O₂/79% N₂), hypercapnic normoxic (HN; 5% CO₂/21% O₂/74% N₂) and hypercapnic hyperoxic (HH; 5% CO₂/95% O₂) gas administration. HH T_1a was calculated by requiring that the HN and HH cerebral blood flow (CBF) change be identical. The HH protocol was then repeated in patients (n = 10; age, 61.4 ± 13.3 years) with intracranial stenosis to assess whether an HH T_1a decrease prohibited ASL from being performed in subjects with known delayed blood arrival times. Arterial blood T_1a decreased from 1.65 s at baseline to 1.49 ± 0.07 s during HH. In patients, CBF values in the affected flow territory for the HH condition were increased relative to baseline CBF values and were within the physiological range (RA CBF = 36.6 ± 8.2 mL/100 g/min; HH CBF = 45.2 ± 13.9 mL/100 g/min). It can be concluded that hyperoxic (95% O₂) 3‐T arterial blood T_1aHH = 1.49 ± 0.07 s relative to a normoxic T_1a of 1.65 s. Copyright © 2015 John Wiley & Sons, Ltd.