PVT Performance Research Articles

Performance validity in the dementia clinic: Specificity of validity tests when used individually and in aggregate across levels of cognitive impairment severity

Objective This study examined the specificity of both individual PVTs and three different PVT batteries in individuals undergoing neuropsychological evaluation for dementia in order to establish both appropriate individual test cutoffs and multiple-PVT failure criterion. Methods Participants were 311 validly performing patients with no cognitive impairment (n = 24), mild cognitive impairment (MCI; n = 115), mild dementia (n = 122), or moderate dementia (n = 50). Cutoffs associated with ≥90% specificity were established for 11 individual PVTs across impairment severity groups. Aggregate false positive rates according to number of PVTs failed were examined for two 4-PVT batteries and one 7-PVT battery. One-way ANOVAs with post-hoc comparisons were conducted for each PVT. Results Performance on 9 of 11 PVTs significantly differed according to impairment severity. PVT cutoffs achieving ≥90% specificity also generally varied by group. For PVTs previously validated in non-dementia samples, slight adjustments from established cutoffs were generally required to maintain adequate specificity in MCI and mild dementia groups, with greater modifications required in the moderate dementia group. A criterion of ≥2 PVT failures resulted in ≥90% specificity in both 4-PVT batteries across groups. In the 7-PVT battery, adequate specificity was achieved with ≥2 failures in MCI and ≥3 failures in the mild dementia group. Conclusions The incorporation and interpretation of several easily assimilated multiple-PVT batteries in dementia evaluations are explored. Additionally, data regarding individual PVT performance according to cognitive impairment severity are provided to aide validity assessment of both patients undergoing dementia evaluation and examinees who are less impaired.

Effects of light transitions on measures of alertness, arousal and comfort

Knowledge on the onset, persistence, and symmetry of effects of lighting transitions on humans is relevant when designing dynamic lighting scenarios and, additionally, can shed light on the dominance of underlying mechanisms. We examined temporal trajectories in measures of alertness, arousal and comfort after abrupt lighting transitions that were created using two strongly contrasting light conditions (warm, dim lighting vs. cool, bright lighting). In this controlled within-subjects experiment, thirtyeight healthy subjects participated in four separate sessions of 90 min. Subjective experiences (alertness, comfort and mood) and objective measures of vigilance (PVT performance), arousal (HR, HRV, SCL), and thermoregulation (skin temperature and DPG) were studied. The comparison of the temporal trajectories following the transition in light for the different variables indicates a complex interplay of underlying physiological and psychological processes driving these effects.

0190 Impact of Menopause-Related Sleep Fragmentation on Daytime Sleepiness and Neurobehavioral Performance: Results of an Experimental Model

Abstract Introduction Cognitive performance may be adversely affected during the menopause transition from hot flash-induced sleep fragmentation even without changes in sleep duration. We examined the effects of experimentally-induced sleep fragmentation without shortened sleep duration on daytime sleepiness and neurobehavioral performance in women in a high and low estradiol (E2) state. Methods Seven pre-menopausal women (29.4 ± 3.8 years) participated in two 6-day inpatient studies repeated in a high-E2 (mid-to-late follicular phase) then low-E2 state (gonadotropin-releasing hormone agonist-induced E2 suppression - similar to levels during menopause) ~6 weeks apart. Sleep was uninterrupted on nights 1–2 [8-h time-in-bed (TIB)] and fragmented on nights 3–5 (9-h TIB) using an auditory stimulus delivered every 15 min that sustained wake for 2 minutes, producing 1-h total wake after sleep onset. Wakefulness was confirmed by event-markers during polysomnographically-recorded sleep episodes. Daytime subjective sleepiness (Karolinska Sleepiness Scale; KSS) and neurobehavioral performance (Psychomotor Vigilance Task; PVT) were assessed every 2–3 hours on study days 2–5. The effects of study day and E2 state on KSS scores and PVT measured reaction time (RT) and attentional failures (RT>500ms) were examined using linear mixed models. Results Participants reported feeling sleepier (+10%), had longer RTs (+22ms), and more attentional failures (+53%) after sleep fragmentation than after uninterrupted sleep (all p<0.001). While there was no main effect of E2 state, there was a differential effect of sleep fragmentation by E2 state on PVT, but not sleepiness, such that the increase in RT and attentional failures in response to sleep fragmentation was only observed in the high-E2 state (p<0.001). Conclusion Eight hours of total sleep time may not be sufficient to maintain subjective sleepiness and PVT performance levels when sleep is not consolidated. These findings have important implications for understanding the role of sleep and E2-modulated cognitive impairment during the menopause transition. Support This work was supported by the NIH: 5R01 AG053838-02 (HJ) and K24-HL105664 (EBK).

The impact of sleep loss on sustained and transient attention: an EEG study.

Sleep is one of our most important physiological functions that maintains physical and mental health. Two studies examined whether discrete areas of attention are equally affected by sleep loss. This was achieved using a repeated-measures within-subjects design, with two contrasting conditions: normal sleep and partial sleep restriction of 5-h. Study 1 compared performance on a sustained attention task (Psychomotor Vigilance task; PVT) with performance on a transient attention task (Attentional Blink; AB). PVT performance, but not performance on the AB task, was impaired after sleep restriction. Study 2 sought to determine the neural underpinnings of the phenomenon, using electroencephalogram (EEG) frequency analysis, which measured activity during the brief eyes-closed resting state before the tasks. AB performance was unaffected by sleep restriction, despite clearly observable changes in brain activity. EEG results showed a significant reduction in resting state alpha oscillations that was most prominent centrally in the right hemisphere. Changes in individual alpha and delta power were also found to be related to changes in subjective sleepiness and PVT performance. Results likely reflect different levels of impairment in specific forms of attention following sleep loss.

Test of variables of attention performance among ADHD children with credible vs. non-credible PVT performance

The assessment of effort is a crucial step in the evaluation of children and adolescents who present with symptoms of an Attention-Deficit/Hyperactivity Disorder (ADHD). Studies with adults have found that a large percentage of individuals claiming to have ADHD fail performance validity measures. In children, failure on PVT measures is associated with lower scores on a wide array of neuropsychological measures. The current study examined the performance of 50 children diagnosed with ADHD on the basis of whether they passed (N = 25) versus failed (N = 25) a standalone PVT, on the Test of Variables of Attention (TOVA), the Wisconsin Card Sorting Test - 64 (WCST) and the Tower of London: Drexel (TOL). Subjects who failed one or more PVTs scored significantly below those who passed, on the Omission scores of the TOVA and on several dimensions of the WCST. No significant differences were found on the TOL scores. Specifically, subjects who failed PVTs scored more than two standard deviations below the mean on the first half TOVA Omission errors score, whereas those who passed PVTs scored within the Average range. It is proposed that first half Omission scores on the TOVA may represent an embedded measure of effort.

The effect of caffeine on cognitive performance is influenced by CYP1A2 but not ADORA2A genotype, yet neither genotype affects exercise performance in healthy adults

PurposeTo determine the influence of two commonly occurring genetic polymorphisms on exercise, cognitive performance, and caffeine metabolism, after caffeine ingestion.MethodsEighteen adults received caffeine or placebo (3 mg kg−1) in a randomised crossover study, with measures of endurance exercise (15-min cycling time trial; 70-min post-supplementation) and cognitive performance (psychomotor vigilance test; PVT; pre, 50 and 95-min post-supplementation). Serum caffeine and paraxanthine were measured (pre, 30 and 120-min post-supplementation), and polymorphisms in ADORA2A (rs5751876) and CYP1A2 (rs762551) genes analysed.ResultsCaffeine enhanced exercise performance (P < 0.001), but effects were not different between participants with ADORA2A ‘high’ (n = 11) vs. ‘low’ (n = 7) sensitivity genotype (+ 6.4 ± 5.8 vs. + 8.2 ± 6.8%), or CYP1A2 ‘fast’ (n = 10) vs. ‘slow’ (n = 8) metabolism genotype (+ 7.2 ± 5.9 vs. + 7.0 ± 6.7%, P > 0.05). Caffeine enhanced PVT performance (P < 0.01). The effect of caffeine was greater for CYP1A2 ‘fast’ vs. ‘slow’ metabolisers for reaction time during exercise (− 18 ± 9 vs. − 1.0 ± 11 ms); fastest 10% reaction time at rest (− 18 ± 11 vs. − 3 ± 15 ms) and lapses at rest (− 3.8 ± 2.7 vs. + 0.4 ± 0.9) (P < 0.05). There were no PVT differences between ADORA2A genotypes (P > 0.05). Serum caffeine and paraxanthine responses were not different between genotypes (P > 0.05).ConclusionCaffeine enhanced CYP1A2 ‘fast’ metabolisers’ cognitive performance more than ‘slow’ metabolisers. No other between-genotype differences emerged for the effect of caffeine on exercise or cognitive performance, or metabolism.

Slow-frequency electroencephalography activity during wake and sleep in obesity hypoventilation syndrome.

Neurophysiological activity during wake and sleep states in obesity hypoventilation (OHS) and its relationship with neurocognitive function is not well understood. This study compared OHS with equally obese obstructive sleep apnea (OSA) patients, with similar apnea-hypopnea indices. Resting wake and overnight sleep electroencephalography (EEG) recordings, neurocognitive tests, and sleepiness, depression and anxiety scores were assessed before and after 3 months of positive airway pressure (PAP) therapy in 15 OHS and 36 OSA patients. Pretreatment, greater slow frequency EEG activity during wake and sleep states (increased delta-alpha ratio during sleep, and theta power during awake) was observed in the OHS group compared to the OSA group. EEG slowing was correlated with poorer performance on the psychomotor vigilance task (slowest 10% of reciprocal reaction times, psychomotor vigilance test [PVT SRRT], primary outcome), and worse sleep-related hypoxemia measures in OHS. There was no between-group significant difference in PVT performance at pre or post-treatment. Similarly, despite both groups demonstrating improved sleepiness, anxiety and depression scores with PAP therapy, there were no differences in treatment response between the OSA and OHS groups. Patients with OHS have greater slow frequency EEG activity during sleep and wake than equally obese patients with OSA. Greater EEG slowing was associated with worse vigilance and lower oxygenation during sleep. This trial was registered with the Australian and New Zealand Clinical Trials Registry (ACTRN12615000122550).

Numerical and experimental investigation of the effect of operating conditions on performance of PVT and PVT-PCM

Irradiations incident on the photovoltaic module are converted only 15–20% into electrical energy and remaining are transformed into heat and drop electrical efficiency. Therefore, to harness both the thermal and electrical energy, hybrid photovoltaic thermal system is an optimum option. Moreover, phase change materials add more advantages of PV cell cooling and heat storage. A novel thermal collector has been designed as PVT and PVT-PCM systems to improve the heat transfer and performance. The 3D numerical analysis is done with COMSOL Multiphysics® software, and is validated at different volume flow rates of 0.5LPM to 3LPM, by experimental investigation at conditions of keeping the inlet water and ambient temperature at 27 °C and solar irradiation at 1000 W/m2. The experiment is carried out in indoor weather under controlled operating parameters and conditions with passive cooling of the module. Maximum 12.4% and 12.28% electrical efficiency of PVT is achieved numerically and experimentally respectively. Similarly, 12.75 and 12.59% electrical efficiency for PVT-PCM is obtained for experimental and numerical cases respectively. For PVT system, 10.13 and 9.2% electrical performance is improved. For PVT-PCM the electrical performance improvement is obtained as 12.91 & 12.75% numerically and experimentally respectively.

0170 Trial-to-Trial inconsistency in Reaction Time on the Psychomotor Vigilance Test Alters Self-Reported Sleepiness

Daytime sleepiness is associated with impaired attention processes, including slower and more variable reaction time. Although results are mixed, recent research has started to show the positive association between insomnia severity, greater daytime sleepiness and impaired simple attention processes. In this study, we aimed to determine whether performance on an attention task influences self-reported sleepiness of individuals across the sleep disturbance spectrum. Participants (N=50) included individuals across the insomnia spectrum from good sleepers to patients with insomnia disorder. Insomnia severity was assessed using the Insomnia Severity Index. Simple attention was assessed using a computerized Psychomotor Vigilance Test (PC-PVT) administered in the morning. Participants’ rated their sleepiness on a scale from 1 (not sleepy) to 10 (extremely sleepy) before and after they completed the PVT. Spearman’s correlation coefficient was used to assess associations between insomnia severity, sleepiness, and PVT performance. Multiple regression was used to determine whether mean or trial-to-trial variability in reaction time predicted post-PVT sleepiness, adjusting for pre-PVT sleepiness and Insomnia Severity Index score. Greater trial-to-trial variability in PVT reaction time predicted greater post-PVT sleepiness after adjusting for pre-PVT sleepiness and insomnia severity, t=2.9, p=0.005. Insomnia symptom severity was associated with greater sleepiness at pre- and post-PVT, rs (50)=0.41, p=0.003 for both. After adjusting for pre-PVT sleepiness, insomnia severity was not a significant predictor of post-PVT sleepiness. Average PVT reaction time was not associated with sleepiness. Participants with greater inconsistency in simple attention performance reported greater sleepiness than they had reported 10 minutes previously. Trial-to-trial variability in reaction time performance may have raised participants’ awareness of their sleepiness. Alternatively, participants with inconsistent performance may have altered their self-report to match their performance. Although insomnia symptom severity was associated with sleepiness it did not make participants more prone to biased sleepiness reports based on performance on the PVT. N/A

0433 Healthy and Depressed Individuals Do Not Differ in Baseline PVT Performance

0433 Healthy and Depressed Individuals Do Not Differ in Baseline PVT Performance

Performance of a demonstration solar PVT assisted heat pump system with cold buffer storage and domestic hot water storage tanks

The design and demonstration of a solar PVT assisted - heat pump system with a cold buffer storage tank on the source side of the heat pump and a hot storage tank for domestic hot water preparation is presented. The system was subject to real weather conditions and hot water draw offs. Measurements over nine months are presented and analyzed. The focus was on the thermal dynamic of the system and the interplay between the heat pump, the storage tanks and the thermal absorber of the uninsulated PVT panel. The hot water demand was almost completely covered by the thermal part of the PVT collector in sunny summer periods. In less sunny periods, the brine-water heat pump recharged the hot water tank after draw offs and discharged the buffer storage tank. The uninsulated PVT collector worked as an energy absorber and was able to extract heat form the ambient air and recharge the buffer storage tank to the ambient air temperature when no solar irradiance was available. In the less sunny and colder periods, the PVT added a significant amount of energy to the cold storage tank.

A Detailed Optimisation of Solar Photovoltaic/Thermal Systems and its Application.

Abstract There have been various studies and experimental results analysing the operational behaviour of PVT, most of which has been done at steady state or quasi-state. Variable factors can be controlled to optimise the PVT output such as mass flow rate, irradiation falling on the PVT through tracking or incidence angles in a day and fixed factors that depend on the design of the chosen PVT system as well as location parameters such as ambient temperature, wind speed, Transport Fluid used, Difference in Structure, Packing Density, Nominal operating temperature, stagnation temperatures, Fill Factor, Thickness of each layer, Location and Latitude and Heat removal factor (harp or serpentine design). The aim of this research is to validate and predict the dynamic behaviour of PVT systems while accurately describing the factor responsible for the loss of efficiency at any point in time under various weather constraints. A commercial system was considered (Solar Angel PVT system) here and is simulated for an entire year. The system was modelled in MATLAB and solved in implicit RK-4 method. The research question finds out to establish the basis for a standard testing protocol for assessing PV-T performance throughout various differences. It also analyses the long-term dynamic performance of PV/T technology by providing evidential data analysis (solar irradiance, heat and electricity, ambient temperature, operational temperatures, flow rates and thermal storage capacity) while completing an assessment of PVT behaviour with respect to an equivalent PV under different weather conditions. The flow rates, heat removal factor and the location affect the thermal behaviour of the PV/T to a greater extent than nominal temperatures and stagnation temperatures.

Numerical and outdoor real time experimental investigation of performance of PCM based PVT system

Photovoltaic power generation is a suitable option to counter depleting and environmentally hazardous fossil fuels. However, increased cell temperature of the photovoltaic module reduces the electrical performance. Therefore, for enhancing the electrical performance as well as to obtain the useful thermal, a combined photovoltaic thermal system is suitable technology. Furthermore, the addition of phase change materials into photovoltaic thermal systems adds more dual benefits in terms of cooling of PV cell as well as heat storage. Hence, there are still issues to transfer heat from the system efficiently, which cause lower performance of PVT and PVT-PCM systems. In this paper, the aluminium material of thermal collector is used by introducing a novel design to enhance heat transfer performance, which is assembled in PVT and PVT-PCM systems. Experimental validation is carried out for the 3D FEM-based numerical analysis with COMSOL Multiphysics® at 200 W/m2 to 1000 W/m2 varying irradiation levels while keeping mass flow rate fixed at 0.5LPM and inlet water temperature at 32 °C. The experiment is carried out at outdoor free weather conditions with passive cooling of the module by an overhead water tank scheme. A good agreement in numerical and experimental results is achieved through experimental validation. Cell temperature reduction of 12.6 °C and 10.3 °C is achieved from the PV module in case of the PVT-PCM system. The highest value of the electrical efficiency achieved is 13.72 13.56% for PV and 13.85 and 13.74% for PVT numerically and experimentally respectively. Similarly, for PVT-PCM, electrical efficiency is achieved as 13.98 and 13.87% numerically and experimentally respectively. In the case of the PVT system, electrical performance is improved as 6.2 and 4.8% and for PVT-PCM, it is improved as 7.2 and 7.6% for numerically and experimentally respectively.

Numerical Performance Investigation of Hybrid PV/Thermal System

Promoting reduction of PV temperature plays crucial role in increasing electrical performance. The present work deal with different types of absorber shape for analysing heat transfer phenomena. Serpentine and spiral absorber are using to verify this purpose with different boundary conditions of inlet mass flow rate and inlet temperatures.The recent study was conducted to evaluate the effect of some operating and designing parameters such as solar radiation levels, flow rates, absorber shape and cooling water temperature on the performance of PVT system numerically. Performance of PVT system determined by thermal efficiency, electrical efficiency and the summation of both known as total or PVT efficiency. Solar radiation ranging from 500 W/m2 to1000 W/m2 was introduced and at each, flow rates of water ranging from 0.016 kg/s to 0.05 kg/s. The results show that the performance of PVT increases with a flow rate at all radiation levels. Also the spiral flow absorber gives a higher performance than serpentine absorber where the value of of spiral absorber is increased by about 5.2% compared to the value of serpentine absorber, on the other hand, the rate of heat loss ( decreased by about 10%.Increasing initial cooling water temperature degrades electrical efficiency of PVT system.

Differential and interacting effects of age and sleep restriction on daytime sleepiness and vigilance in adolescence: a longitudinal study.

There is contradictory evidence on whether sleep need decreases across adolescence. We investigated this question longitudinally with a dose-response design to test the effects of varied sleep durations on daytime sleepiness and on vigilance and to test whether these relations change with age across early and mid-adolescence. Data from 76 participants who completed at least 2 years of the 3-year study are included in this report. Annually, participants ranging in age from 9.8 to 16.2 years completed three different time in bed (TIB) schedules each consisting of four consecutive nights of 7, 8.5, or 10 hours. Daytime sleepiness (multiple sleep latency test [MSLT]) and vigilance (psychomotor vigilance test [PVT]) were measured on the day following the fourth night of each TIB schedule. Electroencephalogram (EEG)-measured sleep durations changed linearly with TIB. MSLT-measured daytime sleepiness decreased with longer TIB and increased with age. The TIB and age effects interacted such that the TIB effect decreased with age. PVT performance improved with longer TIB and improved with age, but the benefit that increased TIB conferred on PVT performance did not change with age. These results seem paradoxical because daytime sleepiness increased but vigilance improved with age. The significant age effect on the relation between TIB and sleepiness compared to the lack of an age effect on the relation between TIB and vigilance performance suggests different rates of maturation in underlying brain systems. We interpret these findings in relation to our model of adolescent brain development driven by synaptic elimination.

The wake maintenance zone shows task dependent changes in cognitive function following one night without sleep.

The interaction between homeostatic sleep pressure and circadian timing modulates the impact of sleep deprivation on cognition. We aimed to investigate how this interaction affects different cognitive functions. Twenty-three healthy volunteers (18 males; mean age = 25.4 ± 5.7 years) underwent 40 hours of sleep deprivation under constant routine conditions. Performance on the Psychomotor Vigilance Test and a cognitive battery assessing vigilant attention, complex attention, recognition memory, and working memory was assessed in the morning (27 hours awake) and evening (37 hours awake) during sleep deprivation and compared to well-rested performance 24 hours earlier. Circadian phase assessments confirmed evening tests occurred in the wake maintenance zone (WMZ). Increased time awake significantly impacted performance on all measures except recognition memory. Post hoc analyses found performance on all measures was significantly impaired in the morning following 27 hours of sleep deprivation compared to well-rested performance 24 hours earlier. In contrast, complex attention and working memory were preserved in the WMZ after 37 hours awake compared to 24 hours earlier, while vigilant attention and PVT performance were significantly impaired. During sleep deprivation, composite scores of speed and accuracy were both impaired in the morning, while only speed was impaired during the WMZ. We observed task- and time-dependent effects of sleep deprivation, such that vigilant attention was significantly impaired after both 27 hours and 37 hours awake (compared to when well-rested at the same circadian clock time). In contrast, complex attention and working memory were impaired at 27 hours awake, but preserved in the WMZ despite increased homeostatic sleep pressure (37 hours awake).

PVT collector technologies in solar thermal systems: A systematic assessment of electrical and thermal yields with the novel characteristic temperature approach

Abstract Photovoltaic-thermal PVT collectors generate solar electricity and heat in a single component. The annual electrical and thermal yields depend in particular on the efficiency of the PVT collector technology, climate, and the type of solar thermal system. This paper provides a systematic comparison of the performance of unglazed, glazed, and PVT collectors with low-emissivity coatings. The yields of these PVT technologies are assessed in four types of solar thermal systems including domestic hot water systems and combi systems in single and multi-family homes at four European locations. For this purpose, an empirical PVT performance model is presented, validated and implemented into TRNSYS. Analyzing the simulation results, the assessed PVT collector technologies reach either high electrical or high thermal yields. This compromise originates from the technological trade-off between a good optical efficiency versus a high level of insulation. Thermally optimized glazed PVT collectors with low-emissivity coatings achieve the highest overall yields and the best energetic utilization of the collector area. These collectors achieve up to three times the electrical output compared to a side-by-side installation of flat plate collectors and PV modules with equal thermal output. The variations between the investigated systems can be attributed to the governing operating temperatures of the PVT collector which are found to be of central relevance. A novel approach puts these temperatures into the focus and introduces the characteristic temperature Tchar as new indicator with a strong correlation to both electrical and thermal yields. This approach can be used to assess electrical and thermal yields of PVT systems and select a suitable collector technology for a given application.

Examination of the Modified Somatic Perception Questionnaire (MSPQ) in a large sample of credible and noncredible patients referred for neuropsychological testing

Objective: The current study evaluated MSPQ sensitivity to noncredible PVT performance in the context of external incentive, and examined MSPQ false positive rates in noncompensation-seeking neuropsychology patients; and investigated effects of ethnicity/culture, gender, and somatoform diagnosis on MSPQ scores, and relationships with PVT and MMPI-2-RF data. Method: MSPQ scores were compared in credible (n = 110) and noncredible (n = 153) neuropsychology referrals. Results: Noncredible patients scored higher than credible patients. When the credible group was divided into those with somatoform orientation (n = 39) versus those without (n = 71), the credible nonsomatoform group scored lower than the other two groups, who did not differ from each other. MSPQ elevations were found in ethnic minorities, and in individuals who learned English as a second language or concurrently with another language. MSPQ elevations were also associated with chronic systemic diseases, neurologic illness, and substance abuse. Women scored higher than men, but men and women were equally represented among those patients scoring beyond cut-offs. MSPQ scores were minimally related to PVT data but were more strongly correlated with MMPI-2-RF scales, particularly over-report validity scales, RC1, and Somatic/Cognitive scales, with more widespread relationships observed in noncredible patients. Conclusions: A cut-off of 18 resulted in few false positives in credible nonsomatoform patients, and appears appropriate for identifying physical symptom over-report (due to malingering or somatoform orientations), with associated sensitivity of 29%. However, clinicians are cautioned regarding using the MSPQ in patients with systemic, neurologic, and substance abuse conditions, and in ethnic minorities and non-monolingual English-speakers.

0208 CIRCADIAN MISALIGNMENT IMPACTS ON HUMAN COGNITIVE PERFORMANCE

Shift work increases the risk for disorders of sleep and human error. Overnight operations pose a challenge because our circadian biology promotes nocturnal sleep and daytime vigilance and performance, which may underlie cognitive vulnerability at night. Here we investigated if daily circadian misalignment, typical for night shift work, adversely impacts cognition across diverse cognitive domains. Thirteen healthy young individuals (27.8 ± 9.5 y; 7 men) underwent two 8-day protocols including either 4 days of circadian alignment (day shifts) or misalignment (night shifts; 12-h inverted behavioral/environmental cycles). Cognitive testing included tasks of sustained attention (Psychomotor Vigilance Task; PVT), cognitive throughput (Addition Task; ADD), information processing (Digit Symbol Substitution Task; DSST) visual-spatial performance (Unstable Tracking-Task; TKT) and declarative memory (Probed Recall Memory; PRM), all of which are sensitive to increased sleep pressure and circadian phase. Circadian misalignment over successive days increased cognitive vulnerability by ~10–20% on sustained attention, cognitive throughput, information processing and visual-motor performance, as compared circadian alignment. Attention, as indexed by PVT performance, was acutely impaired during the first 2 days of misalignment with subsequent improvement after 3 days (interaction of “circadian alignment/misalignment”, “day” and “time since awakening”, p=0.006). Conversely, learning, as indexed by changes in ADD, DSST and TKT performance, significantly improved across multiple days of circadian alignment, while no improvement occurred under misalignment (interaction of “circadian alignment/misalignment” and “day”, p<0.05). Lastly, we investigated if the effects of circadian misalignment on performance were also mediated by prior sleep-wake history. Accordingly, lower sleep efficiency in the sleep episode before cognitive testing significantly impaired performance (interaction of “sleep efficiency”, “circadian alignment/misalignment” and “night”; p<0.05). Our data indicate that daily circadian misalignment may explain cognitive vulnerabilities experienced by night workers, and provide a biological framework for the development of countermeasures against adverse cognitive effects in this vulnerable population. National Heart, Lung, and Blood Institute (NHLBI) Grant R01 HL094806, Clinical Translational Science Award UL1RR025758, and Brigham and Women’s Hospital from the National Center for Research Resources.

Evaluation of the effects of two doses of alpha glycerylphosphorylcholine on physical and psychomotor performance

BackgroundRecent studies have suggested that alpha glycerylphosphorylcholine (A-GPC) may be an effective ergogenic aid. The present study was designed to assess the efficacy of two doses of A-GPC in comparison to placebo and caffeine for increasing countermovement jump performance, isometric strength, and psychomotor function.MethodsForty-eight healthy, college aged males volunteered for the present study and underwent baseline assessment of countermovement jump (CMJ), isometric mid thigh pull (IMTP), upper body isometric strength test (UBIST), and psychomotor vigilance (PVT). Following this assessment participants were randomly assigned to groups consisting of 500 mg A-GPC, 250 mg A-GPC, 200 mg Caffeine or Placebo taken daily. Blood samples were collected 1 h and 2 h post initial dose to quantify serum free choline and thyroid stimulating hormone then subjects returned after 7 days of supplementation to repeat CMJ, IMTP, UBIST and PVT.ResultsNo differences were noted between groups for IMTP, UBIST or PVT performance. Serum free choline was found to be elevated in the two A-GPC groups as compared to placebo (132% and 59% respectively). Serum TSH was found to be significantly depressed in the 500 mg A-GPC group compared to other treatments (p < 0.04). Group differences were noted for maximum velocity and maximum mechanical power on the CMJ (p < 0.05) with the 250 mg A-GPC group demonstrating the greatest improvements in result.ConclusionsBased upon this evidence, and previous evidence regarding A-GPC, it should be considered as an emerging ergogenic supplement.