Introduction to the special section on empirical underpinnings of the ethics of alcohol administration in research settings.

This article introduces the special section of Psychology of Addictive Behaviors that focuses on the ethics of administering alcohol to human research participants, particularly those with a history of alcohol abuse or dependence. It is argued that many assumptions underlying ethical decision making can be put to an empirical test. These assumptions involve the degree to which participants can understand and give informed consent as well as the types and magnitude of possible risks associated with consuming alcohol in a research setting. The research literature relevant to these assumptions is reviewed in this series. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-editing deficits in schizophrenia: A word-association analogue.

Made contrasting predictions to differentiate a 1- from a 2-stage model of word-association performance in schizophrenia. 24 schizophrenics and 24 normals provided word associations in response to (a) "free" vs. "idiosyncratic" instructions, and (b) stimulus words that typically elicit either a strong dominant or several weak associations. Results confirm the 2-stage model: under idiosyncratic instructions, schizophrenics produced more common associations than normals. Findings were consistent with 2 assumptions pertinent to the 2-stage model: schizophrenics (a) sample from an underlying repertoire of nondeviant associations; and (b) are deficient in the ability to edit out sampled but situationally inappropriate associations, whether common or unusual. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further validation of a cigarette purchase task for assessing the relative reinforcing efficacy of nicotine in college smokers.

The authors sought to further validate a cigarette purchase task (CPT), a self-report analogue of a progressive-ratio operant schedule, for the assessment of the relative reinforcing efficacy (RRE) of nicotine in smokers. The measure was assessed in terms of its correspondence to typically observed operant behavior, convergent validity, and divergent validity. Participants were 33 individuals (58% male, age M = 19.30 years) who smoked at least weekly (M = 5.31 cigarettes/day) and underwent a single assessment session. Data from the CPT exhibited the predicted inverse relationship between consumption and price, the predicted relationship between consumption and expenditure, and a heterogeneous pattern of interrelationships among the indices of reinforcement. In addition, 2 indices from the measure, intensity of demand and maximum expenditure for cigarettes, exhibited robust convergent and divergent validity. Although this is an incipient research area and the current study used a relatively small sample, these findings support the validity of a CPT as a time- and cost-efficient method for assessing nicotine reinforcement. Theoretical implications of the findings, limitations, and future directions are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of crystallization of PLA on the thermal and mechanical properties of microfibrillated cellulose-reinforced PLA composites

This paper describes the thermal and mechanical properties of nanocomposites based on polylactic acid (PLA) and microfibrillated cellulose (MFC). The primary objective of this study was to improve the storage modulus of PLA at a high temperature. MFC and PLA were mixed in an organic solvent with various fiber contents up to 20 wt%, followed by drying, kneading and hot pressing into sheets. The nanocomposites were prepared in two different states, fully amorphous and crystallized. Differential scanning calorimetry (DSC) measurements revealed that the presence of MFC accelerates the crystallization of PLA. The tensile modulus and strength of neat PLA were improved with an increase of MFC content in both amorphous and crystallized states. The addition of 20 wt% of MFC in PLA improved the storage modulus of crystallized PLA at a high temperature (120 °C) from 293 MPa to 1034 MPa.     

Analysis of stimulus control treatment of sleep-onset insomnia.

Examined the components responsible for the efficacy of the stimulus control treatment of sleep-onset insomnia. 47 college students with sleep-onset insomnia were assigned to 1 of 5 treatment conditions (stimulus control, noncontingent control, countercontrol, temporal control, and waiting list). Ss were instructed not to expect improvement until after the 4th treatment session. Only stimulus control and a treatment violating the associative aspects of stimulus control produced significantly greater improvement in reported latency to sleep onset than the waiting-list condition. Results are discussed in terms of several possible explanations for improvement due to so-called stimulus control treatment for insomnia. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information encoding and computation with spikes and bursts

Neurons compute and communicate by transforming synaptic input patterns into output spike trains. The nature of this transformation depends crucially on the properties of voltage-gated conductances in neuronal membranes. These intrinsic membrane conductances can enable neurons to generate different spike patterns including brief, high-frequency bursts that are commonly observed in a variety of brain regions. Here we examine how the membrane conductances that generate bursts affect neural computation and encoding. We simulated a bursting neuron model driven by random current input signal and superposed noise. We consider two issues: the timing reliability of different spike patterns and the computation performed by the neuron. Statistical analysis of the simulated spike trains shows that the timing of bursts is much more precise than the timing of single spikes. Furthermore, the number of spikes per burst is highly robust to noise. Next we considered the computation performed by the neuron: how different features of the input current are mapped into specific output spike patterns. Dimensional reduction and statistical classification techniques were used to determine the stimulus features triggering different firing patterns. Our main result is that spikes, and bursts of different durations, code for different stimulus features, which can be quantified without a priori assumptions about those features. These findings lead us to propose that the biophysical mechanisms of spike generation enables individual neurons to encode different stimulus features into distinct spike patterns.     

Reactivity to Alcohol Cues: Isolating the Role of Perceived Availability.

Perceived availability of a substance has been proposed to play a role in cue reactivity by both traditional classical conditioning models and S. T. Tiffany's (1990) cognitive processing model (CPM) of substance use. This study investigated the role of availability information on alcohol cue reactivity. Subjects were 134 heavy drinkers in a 2 × 2 between-subjects design, crossing cues (alcohol vs. neutral) and availability information (availability vs. unavailability). The results indicated significant main effects for cue type, with alcohol cues eliciting greater reactivity on multiple measures, and an interaction effect on the Alcohol Urge Questionnaire (M. J. Bohn, D. D. Krahn, & B. B. Staehler, 1995), such that exposure to alcohol cues in conjunction with unavailability information elicited a greater urge. This was largely a result of changes in self-reported craving and was interpreted as consistent with the CPM. Alternative methodologies and limitations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of removing extracellular Ca2+ on excitation and adaptation in Limulus ventral photoreceptors

In Limulus ventral photoreceptors, removing extracellular calcium (Ca2+o) increases the median latency of light-evoked discrete waves. Removal greatly lengthens the time-to-peak of responses in the dark-adapted cell, but not in the light-adapted cell. Removal does not block light-adaptation or the light-induced rise in intracellular calcium (Ca2+i). These results are interpreted in terms of the hypothesis that both sensitivity and the kinetics of excitation are dependent on Ca2+i, and that Ca2+i is dependent on Ca2+o in the dark-adapted cell, but in the light is dependent largely on Ca2+ released from intracellular compartments.     

Effects of a context shift and multiple context extinction on reactivity to alcohol cues.

Cue exposure treatment (CET) attempts to reduce the influence of conditioned substance cues on addictive behavior via extinction, but has received only modest empirical support in clinical trials. This may be because extinction learning appears to be context dependent and a change in context may result in a return of conditioned responding (i.e., renewal), although this has received only limited empirical examination. The current study used a 4-session laboratory analogue of CET to examine whether a change in context following 3 sessions of alcohol cue exposure with response prevention would result in renewal of conditioned responding. In addition, this study examined whether conducting extinction in multiple contexts would attenuate renewal of conditioned responding. In one-way between-subjects design, 73 heavy drinkers (71% men) were randomized to 3 conditions: (a) single context extinction (extinction to alcohol cues in the same context for 3 sessions followed by a context shift at the fourth session), (b) multiple context extinction (extinction to alcohol cues in different contexts each day for all 4 sessions), and (c) pseudoextinction control condition (exposure to neutral cues in the same context for 3 sessions followed by exposure to alcohol cues at the fourth session). The results revealed the predicted cue reactivity and extinction effects, but the hypotheses that a context shift would generate renewed cue reactivity and that multiple contexts would enhance extinction were not supported. Methodological aspects of the study and the need for parametric data on the context dependency of extinction to alcohol cues are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)