Browsing by Author "Wesensten, Nancy J"
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- ItemCan a mathematical model predict an individual's trait-like response to both total and partial sleep loss?(2015-01-12) Ramakrishnan, Sridhar; Lu, Wei; Laxminarayan, Srinivas; Wesensten, Nancy J; Rupp, Tracy L; Balkin, Thomas J; Reifman, JaquesHumans display a trait like response to sleep loss However it is not known whether this trait like response can be captured by a mathematical model from only one sleep loss condition to facilitate neurobehavioural performance prediction of the same individual during a different sleep loss condition In this paper we investigated the extent to which the recently developed unified mathematical model of performance UMP captured such trait like features for different sleep loss conditions We used the UMP to develop two sets of individual specific models for 15 healthy adults who underwent two different sleep loss challenges order counterbalanced separated by 2 4 weeks i 64 h of total sleep deprivation TSD and ii chronic sleep restriction CSR of 7 days of 3 h nightly time in bed We then quantified the extent to which models developed using psychomotor vigilance task data under TSD predicted performance data under CSR and vice versa The results showed that the models customized to an individual under one sleep loss condition accurately predicted performance of the same individual under the other condition yielding on average up to 50 improvement over non individualized group average model predictions This finding supports the notion that the UMP captures an individual s trait like response to different sleep loss conditions
- ItemDose-dependent model of caffeine effects on human vigilance during total sleep deprivation.(2014-08-05) Ramakrishnan, Sridhar; Laxminarayan, Srinivas; Wesensten, Nancy J; Kamimori, Gary H; Balkin, Thomas J; Reifman, JaquesCaffeine is the most widely consumed stimulant to counter sleep loss effects While the pharmacokinetics of caffeine in the body is well understood its alertness restoring effects are still not well characterized In fact mathematical models capable of predicting the effects of varying doses of caffeine on objective measures of vigilance are not available In this paper we describe a phenomenological model of the dose dependent effects of caffeine on psychomotor vigilance task PVT performance of sleep deprived subjects We used the two process model of sleep regulation to quantify performance during sleep loss in the absence of caffeine and a dose dependent multiplier factor derived from the Hill equation to model the effects of single and repeated caffeine doses We developed and validated the model fits and predictions on PVT lapse number of reaction times exceeding 500 ms data from two separate laboratory studies At the population average level the model captured the effects of a range of caffeine doses 50 300 mg yielding up to a 90 improvement over the two process model Individual specific caffeine models on average predicted the effects up to 23 better than population average caffeine models The proposed model serves as a useful tool for predicting the dose dependent effects of caffeine on the PVT performance of sleep deprived subjects and therefore can be used for determining caffeine doses that optimize the timing and duration of peak performance
- ItemIndividualized performance prediction of sleep-deprived individuals with the two-process model.(2008-02-11) Rajaraman, Srinivasan; Gribok, Andrei V; Wesensten, Nancy J; Balkin, Thomas J; Reifman, JaquesWe present a new method for developing individualized biomathematical models that predict performance impairment for individuals restricted to total sleep loss The underlying formulation is based on the two process model of sleep regulation which has been extensively used to develop group average models However in the proposed method the parameters of the two process model are systematically adjusted to account for an individual s uncertain initial state and unknown trait characteristics resulting in individual specific performance prediction models The method establishes the initial estimates of the model parameters using a set of past performance observations after which the parameters are adjusted as each new observation becomes available Moreover by transforming the nonlinear optimization problem of finding the best estimates of the two process model parameters into a set of linear optimization problems the proposed method yields unique parameter estimates Two distinct data sets are used to evaluate the proposed method Results of simulated data with superimposed noise show that the model parameters asymptotically converge to their true values and the model prediction accuracy improves as the number of performance observations increases and the amount of noise in the data decreases Results of a laboratory study 82 h of total sleep loss for three sleep loss phenotypes suggest that individualized models are consistently more accurate than group average models yielding as much as a threefold reduction in prediction errors In addition we show that the two process model of sleep regulation is capable of representing performance data only when the proposed individualized model is used
- ItemRandomized, double-blind, placebo-controlled, crossover study of the effects of repeated-dose caffeine on neurobehavioral performance during 48 h of total sleep deprivation.(0000-00-00) Hansen, Devon A; Ramakrishnan, Sridhar; Satterfield, Brieann C; Wesensten, Nancy J; Layton, Matthew E; Reifman, Jaques; Van Dongen, Hans P ARATIONALE Caffeine is widely used as a countermeasure against neurobehavioral impairment during sleep deprivation However little is known about the pharmacodynamic profile of caffeine administered repeatedly during total sleep deprivation OBJECTIVES To investigate the effects of repeated caffeine dosing on neurobehavioral performance during sleep deprivation we conducted a laboratory based randomized double blind placebo controlled crossover multi dose study of repeated caffeine administration during 48 h of sleep deprivation Twelve healthy adults mean age 27 4 years six women completed an 18 consecutive day in laboratory study consisting of three 48 h total sleep deprivation periods separated by 3 day recovery periods During each sleep deprivation period subjects were awakened at 07 00 and administered caffeine gum 0 200 or 300 mg at 6 18 30 and 42 h of wakefulness The Psychomotor Vigilance Test and Karolinska Sleepiness Scale were administered every 2 h RESULTS The 200 and 300 mg doses of caffeine mitigated neurobehavioral impairment across the sleep deprivation period approaching two fold performance improvements relative to placebo immediately after the nighttime gum administrations No substantive differences were noted between the 200 mg and 300 mg caffeine doses and adverse effects were minimal CONCLUSIONS The neurobehavioral effects of repeated caffeine dosing during sleep deprivation were most evident during the circadian alertness trough i e at night The difference between the 200 mg and 300 mg doses in terms of the mitigation of performance impairment was small Neither caffeine dose fully restored performance to well rested levels These findings inform the development of biomathematical models that more accurately account for the time of day and sleep pressure dependent effects of caffeine on neurobehavioral performance during sleep loss