Functional connectivity during working memory maintenance

Neurophysiological experiments with monkeys have demonstrated that working memory (WM) is associated with persistent neural activity in multiple brain regions, such as the prefrontal cortex (PFC), the parietal cortex, and posterior unimodal association areas. WM maintenance is believed to require the coordination of these brain regions, which do not function in isolation but, rather, interact to maintain visual percepts that are no longer present in the environment. However, single-unit physiology studies and traditional univariate analyses of functional brain imaging data cannot evaluate interactions between distant brain regions, and so evidence of regional integration during WM maintenance is largely indirect. In this study, we utilized a recently developed multivariate analysis method that allows us to explore functional connectivity between brain regions during the distinct stages of a delayed face recognition task. To characterize the neural network mediating the on-line maintenance of faces, the fusiform face area (FFA) was defined as a seed and was then used to generate whole-brain correlation maps. A random effects analysis of the correlation data revealed a network of brain regions exhibiting significant correlations with the FFA seed during the WM delay period. This maintenance network included the dorsolateral and ventrolateral PFC, the premotor cortex, the intraparietal sulcus, the caudate nucleus, the thalamus, the hippocampus, and occipitotemporal regions. These findings support the notion that the coordinated functional interaction between nodes of a widely distributed network underlies the active maintenance of a perceptual representation.     

What is spiritual? What is spiritual suffering?

The author offers definitions for "spiritual" and for "spiritual suffering," suggesting that human spiritual needs include Love, Faith, Hope, Virtue, and Beauty. Spiritual suffering is experienced when these needs are unfulfilled. Spiritual care involves assisting in the fulfillment of these needs. He considers the constant movement between spiritual needs and fulfillments, encouraging use of fluid (not static) assessment methods using "spiritual spectra." As a model, this outline of basic spiritual needs may serve as the foundation for many current spiritual assessment tools.     

The relationship between acute stress disorder and posttraumatic stress disorder in severely injured trauma survivors

This prospective longitudinal study was designed to investigate the relationship between acute stress disorder (ASD) and the subsequent development of posttraumatic stress disorder (PTSD) in a population of severely injured hospitalised trauma survivors. Symptoms of ASD were assessed just prior to discharge in 307 consecutive admissions to a Level 1 Trauma Centre, with PTSD assessments completed at 3 and 12 months post-injury. A well-established structured clinical interview was adopted for both assessments. Only 1% of the sample met criteria for an ASD diagnosis (at a mean of 8 days post-injury), while the incidence of PTSD was 9% at 3 months and 10% at 12 months. Although all ASD symptom clusters contributed to the prediction of subsequent PTSD severity, logistic regression indicated that only re-experiencing and arousal predicted a categorical PTSD diagnosis. The dissociative symptoms that form the core of ASD were rarely endorsed and showed high specificity but low sensitivity, resulting in a high proportion of false negative diagnoses. Reducing the number of dissociative symptoms required for a diagnosis ameliorated, but did not resolve, the problem. In this particular population, the low sensitivity of the ASD diagnosis renders it a poor screening test for use in identifying high risk individuals for early intervention and prevention strategies.     

An analysis of initial acquisition and maintenance of sight words following picture matching and copy cover, and compare teaching methods

This study compared the copy, cover, and compare method to a picture-word matching method for teaching sight word recognition. Participants were 5 kindergarten students with less than preprimer sight word vocabularies who were enrolled in a public school in the Pacific Northwest. A multielement design was used to evaluate the effects of the two interventions. Outcomes suggested that sight words taught using the copy, cover, and compare method resulted in better maintenance of word recognition when compared to the picture-matching intervention. Benefits to students and the practicality of employing the word-level teaching methods are discussed.     

Effects of anorectic drugs on food intake under progressive-ratio and free-access conditions in rats

The effects of two anorectic drugs, dexfenfluramine and phentermine, on food intake under different food-access conditions were examined. Experiment 1 compared the effects of these drugs on food intake under a progressive-ratio (PR) schedule and free-access conditions. Dexfenfluramine decreased food intake under both conditions, but the doses required to decrease intake under free-access conditions were higher than those required to reduce intake under the PR condition. Intermediate doses of phentermine sometimes increased breaking points, and higher doses decreased them. Phentermine decreased food intake at the same doses under both access conditions. Thus the potency of dexfenfluramine, but not phentermine, to decrease food-maintained behavior depended upon the food-access condition. Experiment 2 used a novel mixed progressive-ratio schedule of food delivery to study the duration of drug effects. Sessions consisted of five components separated by 3-hr timeouts. The ratio requirement reset at the beginning of each component and a new breaking point was obtained. Both dexfenfluramine and phentermine dose-dependently decreased breaking points early in the session. In some rats, compensatory increases in breaking point were observed. That is, breaking points later in the session increased over control levels, resulting in no change in the total number of food pellets earned for the session compared to control. The present findings suggest that the effects of some anorectic drugs depend upon the access conditions for food; increasing the effort to obtain food may enhance their ability to decrease food-maintained behavior.     

Within-session delay-of-reinforcement gradients

Within-session delay-of-reinforcement gradients were generated with pigeons by progressively increasing delays to reinforcement within each session. In Experiment 1, the effects of imposing progressive delays on variable-interval and fixed-interval schedules were investigated while controlling for simultaneous decreases in reinforcer rate across the session via a within-subject yoked-control procedure. Rate of key pecking decreased as a negatively decelerated function of delay of reinforcement within a session. These rate decreases were greater than those during a yoked-interval session in which the rate of immediate reinforcement decreased at the same rate as it did under the progressive-delay procedure. In Experiment 2, delay-of-reinforcement gradients were shallower when the progressive delay intervals were signaled by a blackout than when they were unsignaled. The delay gradients obtained in each experiment were similar to those generated under conditions in which different delays of reinforcement are imposed across blocks of sessions. The present procedure offers a technique for rapidly generating delay-of-reinforcement gradients that might serve as baselines for assessing the effects of other behavioral and pharmacological variables.     

Assessing the distinguishability of models and the informativeness of data

A difficulty in the development and testing of psychological models is that they are typically evaluated solely on their ability to fit experimental data, with little consideration given to their ability to fit other possible data patterns. By examining how well model A fits data generated by model B, and vice versa (a technique that we call landscaping), much safer inferences can be made about the meaning of a model's fit to data. We demonstrate the landscaping technique using four models of retention and 77 historical data sets, and show how the method can be used to: (1) evaluate the distinguishability of models, (2) evaluate the informativeness of data in distinguishing between models, and (3) suggest new ways to distinguish between models. The generality of the method is demonstrated in two other research areas (information integration and categorization), and its relationship to the important notion of model complexity is discussed.     

The role of conceptual recoding in reducing children's retroactive interference

Reductions in children's retroactive interference were examined with conceptual recoding. Children learned two 10-item lists of toys; items on the 2nd list could also be classified as vehicles. Some children were not told about this 2nd category, whereas others were told either at the end of acquisition or just prior to the retention test 24 hr later. The results showed that (a) children benefited from the recoding instruction, (b) younger but not older children failed to benefit from the recoding manipulation when it occurred just prior to the retention test, and (c) recoding reduced retroactive interference primarily through affecting storage processes. These results provide new evidence concerning the importance of making information distinctive in storage in children's retention.     

Emotional-processing in posttraumatic stress disorder II: startle reflex modulation during picture processing

This study examined the impact of a trauma-related stressor on subsequent emotional behavior in veterans with (n = 35) and without (n = 24) posttraumatic stress disorder (PTSD). Self-report and physiological responses, including acoustic startle, were recorded during viewing of emotionally evocative photographs at baseline and following exposure to trauma-related and non-trauma-related stressors. The 2 groups exhibited equivalent patterns of emotional response across self-report and physiological measures at baseline. In contrast, following the trauma challenge, participants with PTSD showed a pattern of startle modulation suggestive of greater defensive reactivity and reduced visual perceptual engagement. These findings, along with augmented corrugator EMG reactivity during the same interval, suggest that trauma-related reexperiencing primes subsequent negative emotional responding in individuals with PTSD.     

Houses built on sand: effects of exemplar stability on susceptibility to attitude change

Attitude representation theory (C. G. Lord & M. R. Lepper, 1999) explains both attitude-behavior consistency and attitude change with the same principles. When individuals respond evaluatively to an attitude object, they activate and combine assumptions about the attitude object with perceptions of the immediate situation. The assumptions activated can vary across time, even without additional information. Previous research has shown that individuals activate exemplars when answering attitude questions, attitude reports vary with the valence of the assumptions activated, and activating differently liked exemplars reduces attitude-behavior consistency. The present research completed study of the theoretical implications of exemplar stability by showing that individuals with temporally unstable exemplars, whether spontaneous (Experiment 1) or manipulated (Experiments 2 and 3), are more susceptible to subsequent attitude change than are individuals with stable exemplars.