Browsing by Author "Kamimori, Gary H"
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- 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
- ItemThe trait of Introversion-Extraversion predicts vulnerability to sleep deprivation.(2007-11-26) Killgore, William D S; Richards, Jessica M; Killgore, Desiree B; Kamimori, Gary H; Balkin, Thomas JAccording to Eysenck s theory of Introversion Extroversion I E introverts demonstrate higher levels of basal activity within the reticular thalamic cortical loop yielding higher tonic cortical arousal than Extraverts who are described conversely as chronically under aroused and easily bored We hypothesized that higher scores on the trait of Extraversion would be associated with greater declines in psychomotor vigilance performance during prolonged wakefulness We evaluated the relationship between I E and overnight psychomotor vigilance performance during 77 h of continuous sleep deprivation in a sample of 23 healthy adult military personnel 19 men four women ranging in age from 20 to 35 years At baseline volunteers completed the Revised NEO Personality Inventory NEO PI R and completed psychomotor vigilance testing at approximately 10 min intervals from 00 15 to 08 50 hours over three nights of continuous sleep deprivation In addition 12 participants received four repeated administrations of caffeine 200 mg every 2 h each night Analysis of covariance and stepwise multiple regression analyses showed that above and beyond the effects of caffeine higher Extraversion was significantly related to more extensive declines in speed of responding and more frequent attentional lapses but only for the first overnight testing session Sub factors of Extraversion including Gregariousness and higher Activity level were most predictive of these changes following sleep loss These findings are consistent with Eysenck s cortico reticular activation theory of I E and suggest that individual differences in the trait of Extraversion confer some vulnerability resistance to the adverse effects of sleep loss on attention and vigilance