An ERP index of task relevance evaluation of visual stimuli

Recently several event-related potential attention studies have described a prefrontal positivity at about the same latency as the posterior N2 (approximately 200-300 ms), variously termed the frontal selection positivity (FSP), the anterior P2 (P2a), or the frontal P3 (P3f). These components have a similar spatio-temporal distribution and similar eliciting properties, suggesting that they represent the same component. However, these components have been differentially interpreted as arising from neural systems of feature selection, stimulus evaluation, or response production. The present study employed a visual target detection (oddball) design with different response conditions: passive (no response), overt (keypress), and covert (silent count), to examine the impact of task relevance and response production on the frontal P2a. The results showed that the P2a was present to task-relevant stimuli but had the same scalp topography and estimated source-dipole locations in both overt and covert responding, indicative of an index of stimulus evaluation, rather than response production.     

A formal model for structuring local perceptions of environmental space

The problem of constructing computational models of space that mimic those found in human spatial reasoning is addressed. This paper extends a formal model that addressed point objects in a 2D world to include the presence of line objects and barriers. The problem consists of determining an appropriate global model for the spatial configuration given a sequence of local views or observations. A formal model is proposed based on constraint network theory. The model leads to the identification of stable regions within which perceptual information about the environment changes slowly, and zones of transition within which the perceptual information changes more quickly. A special case of transition zones is a gateway, which may be viewed as a kind of discontinuity or singularity in the model. It is expected that the model obtained will be used to mimic human mental representations of navigable outdoor environments.     

Perceptual learning in flavor aversion: evidence for learned changes in stimulus effectiveness

Rats were exposed to the compound flavors AX and BX, presented in alternation, and to CX on a separate block of trials. Generalization to BX after aversion conditioning with AX was less than to CX. An equivalent effect was found when the nature of the common element was changed after preexposure but not when the common element was omitted during preexposure, during conditioning and test, or both. Rats conditioned with X alone again showed less aversion to BX than to CX; similarly, rats conditioned with a novel flavor (Y) showed less aversion to BY than to CY. These effects support the proposal that intermixed preexposure to AX and BX enhances the perceptual effectiveness of their unique features, A and B.     

Dissociations among attention, perception, and awareness during object-substitution masking

When a visual target object is surrounded by four dots that onset at the same time as the target but remain visible after the target terminates, the four dots dramatically impair target discrimination performance. This phenomenon is called object-substitution masking , reflecting the hypothesis that both the target and the four dots are identified, but the representation of the four dots replaces the representation of the target object before the target can be reported. The present study used the event-related potential technique to demonstrate that a target masked in this manner is identified by the visual system and triggers a shift of attention. However, by the time attention is shifted to the target, only the mask remains visible, leading to impaired behavioral detection performance. These findings support the object-substitution hypothesis and provide new evidence that perception, attention, and awareness can be dissociated.     

Lesions of orbitofrontal cortex and basolateral amygdala complex disrupt acquisition of odor-guided discriminations and reversals

Recent work indicates that both orbitofrontal cortex (OFC) and the basolateral complex of the amygdala (ABL) are involved in processes by which cues are associated with predicted outcomes. To examine the respective roles of these structures in discrimination learning, rats with bilateral sham or neurotoxic lesions of either OFC or ABL were trained on a series of four 2-odor discrimination problems in a thirst-motivated go, no-go task. After acquisition of the series of odor problems, the rats were trained on serial reversals of the final odor problem. Performance on each problem was assessed by monitoring accuracy of choice behavior, and also by measuring latency to respond for fluid outcomes after odor sampling. During discrimination learning, rats in both lesioned groups had similar deficits, failing to show normal changes in response latency during learning, while at the same time exhibiting normal choice behavior relative to controls. Choice behavior was affected only during the reversal phase of training, in which OFC and ABL lesions produced distinctive deficits. Rats with ABL lesions were impaired on the first reversal (S1−/S2+), but were unimpaired at acquiring a reversal back to the original odor-outcome contigencies (S1+/S2−), whereas rats with OFC lesions were impaired on both types of reversals. These findings suggest that OFC and ABL serve partially overlapping roles in the use of incentive information that supports normal discrimination performance.     

Perceptual organization influences visual working memory

Previous studies have demonstrated that top-down factors can bias the storage of information in visual working memory. However, relatively little is known about the role that bottom-up stimulus characteristics play in visual working memory storage. In the present study, subjects performed a change detection task in which the to-be-remembered objects were organized in accordance with Gestalt grouping principles. When an attention-capturing cue was presented at the location of one object, other objects that were perceptually grouped with the cued object were more likely to be stored in working memory than were objects that were not grouped with the cued object. Thus, objects that are grouped together tend to be stored together, indicating that bottom-up perceptual organization influences the storage of information in visual working memory.     

Multisystemic therapy for young offenders: families' experiences of therapeutic processes and outcomes

Multisystemic Therapy (MST) has been found to be effective in reducing youth antisocial behavior, but little is known about the process and impact of MST from the perspective of families themselves. This qualitative study explored parents' and young people's experiences of MST, focusing on aspects of the intervention that promoted or limited change. Thirty-seven semistructured interviews were conducted with a consecutive sample of 21 families (21 parent interviews, 16 young people) who had participated in a randomized controlled trial of MST for young offenders in the United Kingdom. Thematic analysis yielded 10 themes, organized into two domains: (a) engagement in MST and initial processes of change captures the central importance of the therapeutic relationship and the MST engagement model in families' positive experiences of MST; and (b) outcomes are complex reflects the range of positive outcomes reported (notably increased parental confidence and skills, improved family relationships, a return to education, and greater reflection and aspiration on the part of the young person) and mixed behavior outcomes. Even when the young person had reoffended, respondents indicated a range of other benefits for the family. The findings support the MST theory of change as well as point to some outcomes not usually measured in MST outcome studies. They also suggest some adaptations that may increase the impact of the intervention, including more attention to the influence of deviant peers, and ongoing support for families struggling to maintain strategies beyond the prescribed treatment period.     

Diversity is what you want it to be: how social-dominance motives affect construals of diversity

We propose that diversity is a malleable concept capable of being used either to attenuate or to enhance racial inequality. The research reported here suggests that when people are exposed to ambiguous information concerning an organization's diversity, they construe diversity in a manner consistent with their social-dominance motives. Specifically, anti-egalitarian individuals broaden their construal of diversity to include nonracial (i.e., occupational) heterogeneity when an organization's racial heterogeneity is low. By contrast, egalitarian individuals broaden their construal of diversity to include nonracial heterogeneity when an organization's racial heterogeneity is high. The inclusion of occupational heterogeneity in perceptions of diversity allows people across the spectrum of social-dominance orientation to justify their support for or opposition to hierarchy-attenuating affirmative-action policies. Our findings suggest that diversity may not have a fixed meaning and that, without a specific delineation of what the concept means in particular contexts, people may construe diversity in a manner consistent with their social motivations.     

Impulse Control Disorders in Parkinson’s Disease: A Psychosocial Perspective

Parkinson's disease (PD) is a progressive neurodegenerative disease primarily characterised by motor symptoms. However, another feature of PD which is receiving increasing attention is the phenomenon of impulse control disorders (ICDs), such as pathological gambling. To date, research into ICDs in PD has centred on a biomedical model of cause, related to the effects of dopamine replacement therapy. However, there are several areas of discrepancy in the current biomedical account of ICDs in PD. In addition, we argue that social and psychological factors also need to be considered to achieve a more complete understanding of the phenomenon. We present a novel conceptual model which combines biomedical and psychosocial factors in the genesis of ICDs in PD and use the model to identify a number of potential treatment intervention points and to highlight important outstanding questions concerning the inter-relationship between psychosocial and biomedical factors in the genesis of ICDs in PD.