伏隔核和中脑腹侧被盖区内食欲素在吗啡奖赏中的作用

实验采用条件性位置偏爱（CPP）模型考察中脑腹侧被盖区（VTA）和伏隔核壳区（NAcSh）内食欲素（orexin）在吗啡奖赏中的作用。Wistar大鼠分为盐水训练组和吗啡训练组。3轮吗啡（或盐水）匹配训练前,双侧VTA或NAcSh内给予OXR1拮抗剂SB334867（VTA: 0, 1, 5μg;NAcSh: 0, 1, 3μg）;或2轮吗啡（或盐水）匹配训练前NAcSh内给予orexin A（0, 2, 4, 6μg）,观察其对吗啡CPP建立的影响。结果表明,VTA内给予SB334867抑制吗啡CPP建立,并存在剂量效应关系;NAcSh内给予SB334867或orexin A均未影响吗啡CPP建立,而orexin A可增加吗啡处理大鼠的运动性。以上结果表明,VTA和NAcSh内的orexin在吗啡奖赏中扮演的角色不同,可能调控成瘾行为的不同成分     

Neural mechanisms of social influence

The present investigation explores the neural mechanisms underlying the impact of social influence on preferences. We socially tagged symbols as valued or not – by exposing participants to the preferences of their peers – and assessed subsequent brain activity during an incidental processing task in which participants viewed popular, unpopular, and novel symbols. The medial prefrontal cortex (mPFC) differentiated between symbols that were and were not socially tagged – a possible index of normative influence – while aspects of the striatum (the caudate) differentiated between popular and unpopular symbols – a possible index of informational influence. These results suggest that integrating activity in these two brain regions may differentiate objects that have become valued as a result of social influence from those valued for non-social reasons.     

The susceptibility of mental accounting principles to evaluation mode effects

The present research shows that the predictions and outcomes of mental‐accounting tests depend on whether preferences are measured separately (one at a time) or jointly (comparatively). Across five studies, we show that joint evaluation weakens some decision biases (the theater ticket problem, the calculator and jacket problem), but exacerbates others (the basketball game problem). Joint evaluations serve as a check on whether people think the answers they give in separate evaluations make sense or require adjustment. We discuss how the findings impact (1) tests of mental accounting predictions (between vs. within subjects designs), and (2) the normative status of mental accounting. Copyright © 2008 John Wiley & Sons, Ltd.     

Construct validity of the medical specialty preference inventory: A critical analysis

The Medical Specialty Preference Inventory (MSPI; Zimny, G.H. (1979). Manual for the Medical Specialty Preference Inventory. St. Louis, MO: St. Louis University School of Medicine), a measure of medical students’ interests, was substantively and empirically examined to identify an underlying factor structure. A factor model for the original MSPI based on 38 factors in five general areas was evaluated on a national sample of 1014 medical students and yielded poor fit to the data. Exploratory factor analyses at the item level utilizing the full pool of MSPI items produced an 11 factor solution with 88 items. Sub-scales were identified within this model and an 11-18 higher-order model and an 18 sub-scale model also were proposed. The relative fits of the three models were evaluated by confirmatory factor analysis with the 18 sub-scale model shown to be superior. This model was cross-validated on a separate sample of 1016 medical students and fit the data well. All sub-scales exhibited adequate internal consistency across samples. These findings support the need for a revised MSPI based on 18 scales. Implications of these findings for MSPI scoring practices are discussed along with future directions.     

Predictive validity of the medical specialty preference inventory

Medical schools can assist students by providing them with quality career counseling to help them choose a medical specialty. Many schools use interest inventories to help identify students’ specialty interests. This study examined the predictive validity of one such inventory, the Medical Specialty Preference Inventory (MSPI). In a longitudinal design, we used discriminant function analysis to examine how well students’ scores on the MSPI fit their chosen medical specialty one year later. The MSPI correctly predicted students’ future medical specialty choice 58.1% of the time. These results can help career advisors interpret MSPI scores, and identify students’ most likely medical specialty choice, as well as their second most likely choice.     

Super-latent inhibition of conditioned taste preference with a long retention interval

A long delay inserted between conditioning and test phases of a 3-stage Latent Inhibition (LI) procedure produces differential effects on LI depending on the delay context. Thus, enhanced LI has been obtained when the delay is spent in a context that is different from the remaining experimental contexts, but not when it is the same. The present paper examined the effect of delayed testing using a conditioned taste preference procedure. In Experiment 1, three groups received preexposure to either water, or almond, or citrus solutions. Subsequently, the animals were conditioned by pairing the almond and the citrus solutions with sucrose. In a two-bottle preference test conducted 1 day after conditioning, the preexposed flavored solutions were consumed less than the non-preexposed flavors (LI). Experiments 2 and 3 used the same basic procedure, but varied the retention interval duration (1 and 21 days) and the delay context, similar (Experiment 2) and different (Experiment 3) from that of the other stages of the experiments. LI was greater after the long than the short-retention interval when the context was different, thereby demonstrating super-LI. The results were explained by a time-induced context differentiation process.     

DYNAMICS OF CHOICE: RELATIVE RATE AND AMOUNT AFFECT LOCAL PREFERENCE AT THREE DIFFERENT TIME SCALES

To examine extended control over local choice, the present study investigated preference in transition as food‐rate ratio provided by two levers changed across seven components within daily sessions, and food‐amount ratio changed across phases. Phase 1 arranged a food‐amount ratio of 4:1 (i.e., the left lever delivered four pellets and the right lever one pellet); Phase 2 reversed the food‐amount ratio to 1:4, and in Phase 3 the food‐amount ratio was 3:2. At a relatively extended time scale, preference was described well by a linear relation between log response ratio and log rate ratio (the generalized matching law). A small amount of carryover occurred from one rate ratio to the next but disappeared after four food deliveries. Estimates of sensitivity to food‐amount ratio were around 1.0 and were independent of rate ratio. Analysis across food deliveries within rate‐ratio components showed that the effect of a small amount was diminished by the presence of a large amount—that is, when a larger amount was present in the situation (three or four pellets), the value of a small amount (one or two pellets) became paltry. More local analysis of visits to the levers between food deliveries showed that postfood visits following a large amount were disproportionately longer than following a small amount. Continuing food deliveries from the same source tended to make visits less dependent on relative amount, but a discontinuation (i.e., food from the other lever) reinstated dependence on relative amount. Analysis at a still smaller time scale revealed preference pulses following food deliveries that confirmed the tendency toward dependence on absolute amount with continuing deliveries, and toward dependence on relative amount following discontinuations. A mathematical model based on a linear‐operator equation accounts for many of the results. The larger and longer preference following a switch to a larger amount is consistent with the idea that local preference depends on relatively extended variables even on short time scales.     

CONSUMPTION AND RESPONSE OUTPUT AS A FUNCTION OF UNIT PRICE: MANIPULATION OF COST AND BENEFIT COMPONENTS

We conducted preference assessments with 4 typically developing children to identify potential reinforcers and assessed the reinforcing efficacy of those stimuli. Next, we tested two predictions of economic theory: that overall consumption (reinforcers obtained) would decrease as the unit price (response requirement per reinforcer) increased and that the cost and benefit components that defined unit price would not influence overall consumption considerably when unit price values were equal. We tested these predictions by arranging unit price such that the denominator was one (e.g., two responses produced one reinforcer) or two (e.g., four responses produced two reinforcers). Results showed that consumption decreased as unit price increased and that unit price values with different components produced similar consumption.     

Pulling yourself together: Meditation promotes congruence between implicit and explicit self-esteem

Self-reported or explicit self-esteem frequently conflicts with indirectly assessed, implicit self-esteem. The present research investigated whether meditation may reduce such inner conflicts by promoting congruence between implicit and explicit self-esteem. Relative to control conditions, meditation led to greater congruence between explicit self-esteem, assessed via self-report, and implicit self-esteem, indicated by name-letter preference (Studies 1 and 2). Low implicit self-esteem was further associated with a slow-down of explicit self-evaluation (Study 2), an effect that mediated the greater congruence between implicit and explicit self-esteem in the meditation condition. These results suggest that meditation encourages people to rely more on intuitive feelings of self-worth.     

The role of familiarity in dietary development

The rise in inadequate and unhealthily diets in children has led investigations to examine the development of food preferences. This review outlines the ways in which children choose between foods made available to them and the subsequent shaping of their own habitual diet. Children are liable to form preferences to certain hedonic foods, and to exhibit neophobic reactions to the unfamiliar. Unfamiliar foods can elicit anxiety and suspicion. Trust and liking of a once novel food can be gained through exposure, increasing familiarity towards that food. This review examines: visual familiarity (awareness of foods within their environment); taste familiarity (knowledge and experience of the taste of foods); contextual familiarity (knowledge of how foods should be presented); and categorical familiarity (which family foods belong to). The influence of familiarity is also explained with regards to both positive and negative associative learning. These associations are influenced by the specific presentation and the social environment of a novel food. The potential benefits of understanding the nature of children’s learning and preference development for the promotion of healthy nutrition to both parent and child are discussed.