Biomedical subjects

Steven R Hursh

Publications and source records attributed to Steven R Hursh.

6 recordsLinked to original sources

PubMed2006

Behavioral economic analysis of opioid consumption in heroin-dependent individuals: effects of unit price and pre-session drug supply.

Behavioral economic analysis has been used to investigate factors underlying drug consumption in laboratory animals and, increasingly, in human drug abusers. However, there are few studies in heroin abusers, especially those who are not in treatment; such studies may be valuable for understanding the mechanisms of persistent drug use. This study investigated effects of unit price (UP) and pre-session supply of hydromorphone (HYD) on choice and consumption of HYD. Heroin-dependent research volunteers (n=13) stabilized on buprenorphine 8 mg/day completed this eight-session inpatient study. In sessions 1-2, participants sampled two total HYD doses (12 and 24 mg IM) that could be earned in later sessions. In each of the final six sessions, volunteers were given access to a 12-trial choice progressive ratio schedule lasting 3h. On each trial, volunteers could earn a HYD unit dose (1 or 2 mg, for a maximum of 12 or 24 mg, respectively) or money (US dollars 2, for a maximum of US dollars 24). Fixed ratio requirements increased exponentially, generating 24 unit prices for behavioral economic analysis. Before some choice sessions, volunteers could choose (FR 1) to receive extra HYD (12 or 24 mg; at 0915), whereas on other days no supplement was available. HYD choice and peak responding (breakpoint, O(max)) measures increased with unit dose, decreased with pre-session supplements, and were greater among volunteers who used cocaine prior to the experiment. Taking pre-session supplements decreased P(max) and made group-percent HYD consumption more demand-elastic. Consumption was functionally equivalent at differing FR/unit dose combinations. Thus, opioid demand in heroin-dependent individuals not in treatment is a function of drug supply, unit price, and cocaine use.

Adolescent↗

PubMed2006

Assessing unit-price related remifentanil choice in rhesus monkeys.

Given a commodity available at different prices, a unit-price account of choice predicts preference for the cheaper alternative. This experiment determined if rhesus monkeys preferred remifentanil (an ultra-short-acting micro-opioid agonist) delivered at a lower unit price over a higher-priced remifentanil alternative (Phases 1 and 3). Choice between equal-priced alternatives also was assessed (Phase 2). A discrete-trials procedure was arranged in which three monkeys chose between two remifentanil alternatives by responding on one of two levers. Different prices were arranged by manipulating drug dose (0.3 and 0.1 microg/kg/injection) and/or the ratio requirement. Monkeys usually chose the larger-dose alternative even when it was more expensive. Only when unit prices were relatively high (e.g., large response requirements) did monkeys choose the cheaper (or equally priced) smaller-dose alternative. Employing larger doses (0.9 and 0.3 microg/kg/injection) attenuated the larger-dose preference. The results demonstrate that choice was not determined simply by unit price. An alternative model that employs demand-function analysis to generate choice predictions is proposed.

Analgesics, Opioid↗

PubMed2005

The economics of drug abuse: a quantitative assessment of drug demand.

Behavioral economic concepts have proven useful for an overall understanding of the regulation of behavior by environmental commodities and complements a pharmacological perspective on drug abuse in several ways. First, a quantitative assessment of drug demand, equated in terms of drug potency, allows meaningful comparisons to be made among drug reinforcers within and across pharmacological classes. Second, behavioral economics provides a conceptual framework for understanding key factors, both pharmacological and environmental, that contribute to reductions in consumption of illicit drugs. Finally, behavioral economics provides a basis for generalization from laboratory and clinical studies to the development of novel behavioral and pharmacological therapies.

Animals↗

PubMed2004

Distributed interactive communication in simulated space-dwelling groups.

This report describes the development and preliminary application of an experimental test bed for modeling human behavior in the context of a computer generated environment to analyze the effects of variations in communication modalities, incentives and stressful conditions. In addition to detailing the methodological development of a simulated task environment that provides for electronic monitoring and recording of individual and group behavior, the initial substantive findings from an experimental analysis of distributed interactive communication in simulated space dwelling groups are described. Crews of three members each (male and female) participated in simulated "planetary missions" based upon a synthetic scenario task that required identification, collection, and analysis of geologic specimens with a range of grade values. The results of these preliminary studies showed clearly that cooperative and productive interactions were maintained between individually isolated and distributed individuals communicating and problem-solving effectively in a computer-generated "planetary" environment over extended time intervals without benefit of one another's physical presence. Studies on communication channel constraints confirmed the functional interchangeability between available modalities with the highest degree of interchangeability occurring between Audio and Text modes of communication. The effects of task-related incentives were determined by the conditions under which they were available with Positive Incentives effectively attenuating decrements in performance under stressful time pressure.

Adaptation, Psychological↗

PubMed2004

Fatigue models for applied research in warfighting.

The U.S. Department of Defense (DOD) has long pursued applied research concerning fatigue in sustained and continuous military operations. In 1996, Hursh developed a simple homeostatic fatigue model and programmed the model into an actigraph to give a continuous indication of performance. Based on this initial work, the Army conducted a study of 1 wk of restricted sleep in 66 subjects with multiple measures of performance, termed the Sleep Dose-Response Study (SDR). This study provided numerical estimation of parameters for the Walter Reed Army Institute of Research Sleep Performance Model (SPM) and elucidated the relationships among several sleep-related performance measures. Concurrently, Hursh extended the original actigraph modeling structure and software expressions for use in other practical applications. The model became known as the Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) Model, and Hursh has applied it in the construction of a Fatigue Avoidance Scheduling Tool. This software is designed to help optimize the operational management of aviation ground and flight crews, but is not limited to that application. This paper describes the working fatigue model as it is being developed by the DOD laboratories, using the conceptual framework, vernacular, and notation of the SAFTE Model. At specific points where the SPM may differ from SAFTE, this is discussed. Extensions of the SAFTE Model to incorporate dynamic phase adjustment for both transmeridian relocation and shift work are described. The unexpected persistence of performance effects following chronic sleep restriction found in the SDR study necessitated some revisions of the SAFTE Model that are also described. The paper concludes with a discussion of several important modeling issues that remain to be addressed.

Aviation↗

PubMed2004

Modulating the homeostatic process to predict performance during chronic sleep restriction.

BACKGROUND: In most current sleep/performance models, the homeostatic process is generally conceived as a simple reservoir in which performance capacity increases exponentially during sleep and decays either linearly or exponentially during wakefulness. Models that include this notional homeostatic process have been successful for describing sleep-performance data under conditions of irregular sleep schedules, jet lag, and short periods of total sleep loss. However, recently described data from sleep restriction studies indicate that recovery following chronically restricted sleep is considerably slower than would be predicted by these models. These findings suggest that chronic sleep restriction induces relatively long-term, slow-recovering changes in brain physiology that affect alertness and performance. METHODS: This paper describes, both conceptually and mathematically, a generic modification to sleep/performance models that facilitates the ability to predict the rate at which alertness and performance restoration occurs during recovery sleep following chronic sleep restriction. Weighted nonlinear least-squares methods were used to compare the proposed modulated homeostatic model with recent sleep/performance observations during chronic sleep restriction and recovery. RESULTS: When compared with the classical Walter Reed homeostatic model, this proposed model was found to provide a better description of sleep restriction and recovery observations. The proposed model was also found to be consistent with the data from a recent University of Pennsylvania study. CONCLUSIONS: These two models make significantly different predictions of performance during both the recovery phase and the chronic sleep restriction phase.

Data Interpretation, Statistical↗