Three predictions of the economic concept of unit price in a choice context

Economic theory makes three predictions about consumption and response output in a choice situation: (a) When plotted on logarithmic coordinates, total consumption (i.e., summed across concurrent sources of reinforcement) should be a positively decelerating function, and total response output should be a bitonic function of unit price increases; (b) total consumption and response output should be determined by the value of the unit price ratio, independent of its cost and benefit components; and (c) when a reinforcer is available at the same unit price across all sources of reinforcement, consumption should be equal between these sources. These predictions were assessed in human cigarette smokers who earned cigarette puffs in a two-choice situation at a range of unit prices. In some sessions, smokers chose between different amounts of puffs, both available at identical unit prices. Individual subjects' data supported the first two predictions but failed to support the third. Instead, at low unit prices, the relatively larger reinforcer (and larger response requirement) was preferred, whereas at high unit prices, the smaller reinforcer (and smaller response requirement) was preferred. An expansion of unit price is proposed in which handling costs and the discounted value of reinforcers available according to ratio schedules are incorporated.     

Effects of compounding drug-related stimuli: escalation of heroin self-administration

Previous experiments have demonstrated that presenting independently established discriminative stimuli in compound can substantially increase operant responding maintained by food reinforcement or shock avoidance. Recently, this phenomenon was also shown to occur with cocaine self-administration. The present study further assessed the generality of these stimulus-compounding effects by systematically replicating them with heroin self-administration. Rats' nose-poke responses produced intravenous heroin (0.025 mg/kg per infusion) on a variable-ratio schedule when either a tone or a light was present. In the absence of these stimuli, responding was not reinforced. Once discriminative control by the tone and light had been established, the stimuli were presented in compound under extinction (with heroin discontinued) or maintenance conditions (with heroin available during test-stimulus presentations). In extinction, the tone-light compound increased responding approximately threefold compared to tone or light alone. Under maintenance conditions, compounding increased heroin intake approximately twofold. These effects closely matched those obtained earlier with cocaine. This consistency across pharmacological classes and across drug and nondrug reinforcers further confirms that (a) self-administered drugs support conditioning and learning in a manner similar to that supported by other reinforcers; and (b) multiple drug-related cues interact in lawful and predictable ways to affect drug seeking and consumption.     

Super Pill is Less Effective than an Ordinary Mint in Altering Subjective Psychological Feeling States within a Few Minutes

Expectations shape human behavior. Initial drug use might be associated with information-based expectations. In this study, we presumed that changes in affect and perceived physical wellbeing will be stronger after receiving an active placebo (Tic Tac mint; n = 40), than a pure placebo (inert pill; n = 40) given as a mood-enhancing “super pill.” After baseline measures, participants completed a treatment-expectancy scale, ingested the mint/super pill, and attended to the effects over 3-minutes. Subsequently, they completed again the psychological tests. Expectancy scores were positive and did not differ between the groups. The pure placebo group increased in physical wellbeing but less than the active placebo group, which also showed an increase in positive affect. Negative affect decreased in both groups. The Tic Tac produced greater affective changes than the pure placebo. Since these are new findings on the ultra-short placebo effects on affect, the results might have relevance for drug-use studies.     

Illicit Drug Use,Cognitive Distortions,and Suicidal Ideation Among Homeless Youth: Results From a Randomized Controlled Trial

Illicit drug use and cognitive distortions confer significant risks to youth suicidal thoughts and behaviors. However, there has been limited evidence regarding the efficacy of suicide prevention interventions with homeless youth, especially studies testing whether such interventions can reduce the risk for suicidal ideation associated with illicit drug use. Suicidal homeless youth (N = 150) between the ages of 18 to 24 years were recruited from a drop-in center. Youth were randomly assigned to Cognitive Therapy for Suicide Prevention (CTSP) + Treatment as Usual (TAU) or TAU alone. Youth reported their illicit drug use, cognitive distortions, and suicidal ideation 4 times over 9 months. A multiple-group multilevel structural equation model showed that higher illicit drug use at baseline predicted a slower reduction in cognitive distortions and suicidal ideation in the TAU group. These associations were not found in the CTSP + TAU group, suggesting an interruption of such risk from illicit drug use. Findings suggest that CTSP can reduce the risk of illicit drug use as a treatment barrier towards cognitive distortions and suicidal ideation among homeless youth, with implications to improve treatment efforts and to reduce premature mortality in a vulnerable population.     

Similar consumption and responding across single and multiple sources of drug

Two experiments were conducted to assess whether total response output and total consumption would be similar when drugs are available from single and multiple sources of reinforcement, as predicted by behavioral economics. In Experiment 1, cigarette-deprived smokers were exposed to a concurrent-chains schedule in which equal fixed-ratio schedules served as the initial links, and different reinforcer magnitudes (i.e., number of cigarette puffs) were arranged across alternatives. After the session, obtained unit price was calculated and imposed in the next session when a different number of puffs was available according to a single fixed-ratio schedule. Thus, the unit price at which cigarette puffs could be earned was yoked within subjects across the single and concurrent-chains schedules. When plotted as a function of unit price, similar consumption and response rates were usually obtained across these schedules. Experiment 2 addressed a weakness of Experiment 1, namely, that responding was allocated exclusively to the larger reinforcer magnitude in concurrent-chains conditions, and therefore this schedule may have functioned as a single schedule. In Experiment 2, subjects were instructed to alternate responding between the two alternative schedules. Instructions produced approximately equal response allocation between the two alternatives. Again, similar consumption and response rates were observed across the single and instructed concurrent-chains schedules. These findings are discussed in the context of direct effects and behavioral economics perspectives of drug self-administration.     

铜绿假单胞菌I类整合子及耐药基因分析

铜绿假单胞菌是临床上重要的院内感染菌,对多种抗生素耐药。整合子是能捕获并整合外源耐药基因盒,并使之表达的DNA元件。通过整合子水平转移的方式极大地加速了耐药基因在同种及不同种属之间的传播,造成细菌的耐药以至多重耐药问题日益严重。     

Drug discrimination: stimulus control during repeated testing in extinction

Rats were trained, under a two-lever drug-discrimination procedure, to respond differentially depending upon whether lorazepam (1.0 mg/kg) or no injection had been administered before the session. Responses on the appropriate lever produced a food pellet under a modified fixed-ratio (FR) 10 schedule, in which the 10 responses had to be emitted consecutively. In reinforcement tests, completing an FR 10 on either lever produced a pellet. In extinction tests, stimulus changes paired with reinforcement occurred but no pellet was delivered. Training sessions were conducted between test sessions. Each of four extinction phases consisted of six tests preceded by one stimulus (e.g., lorazepam). Repeated exposures to extinction reduced response rates for all rats, but stimulus control, as inferred from either percentage of total responses or percentage of total FR 10s on the drug-appropriate lever, remained high. The percentage of total FR 10s measure was less subject to skewing under low-rate conditions than was the percentage of total responses measure and provided an evaluation of stimulus control in terms of meeting the consecutive response contingency. These results demonstrate a level of independence between response rate and stimulus control in drug discrimination, which has positive implications for the validity of interpreting discriminative effects of novel test conditions in well-trained animals, even when overall response rates are low.     

THE ACCELERATED INTAKE: A METHOD FOR INCREASING INITIAL ATTENDANCE TO OUTPATIENT COCAINE TREATMENT

We examined whether offering an accelerated (same-day) versus a standard (1- to 7-day delay) intake appointment increased initial attendance at an outpatient cocaine treatment program. Significantly more of the subjects who were offered an accelerated intake (59%) attended than those who were given a standard intake (33%), χ² (2, N = 78) = 4.198, p < .05. The accelerated intake procedure appears to be useful for enhancing enrollment in outpatient addiction treatment.     

药物成瘾行为的脑机制及其研究进展

药物成瘾是脑内相关核团和细胞在药物反复作用下发生适应性变化的时间依赖过程。成瘾的适应性学说从ｃＡＭＰ水平调节、阿片和多巴胺受体与Ｇ蛋白家族耦联等方面,为成瘾形成机制提供了最基本的生物学范畴的理论解释。实验证据在一定程度上揭示了从给药到耐受、敏感、依赖,再到撤药症状的生物变化过程。然而,阐明从急性给药到特殊脑区持续性的适应机制仍然是当前成瘾研究最具挑战性的目标之一。     

临床药师参与临床决策的有限理性分析

为了提高临床药师工作质量,在有限理性视阈下探析临床药师工作的特点。临床药师参与临床查房、疑难病例讨论、药品不良反应分析与处置、药物重整、患者用药教育等临床决策具有一定的理性特性,但是这种理性属于有限理性。医疗机构决策者应该重视培养临床药师的思维活动过程,重视临床药师投入的沉淀成本;同时,临床药师自身要提高临床决策的满意标准和重视临床决策目的的层级结构关系。通过以上的做法对临床药师队伍发展有积极的促进作用。