A simple cell model with dominating opponent inhibition for robust contrast detection

Ein Modell kortikaler Einfachzellen mit dominanter opponenter Inhibition zur robusten Kontrastdetektion Zusammenfassung. Im primären visuellen Pfad wird Information in zwei getrennten, komplementären Domänen repräsentiert, den on- und off-Zellen. In dieser Arbeit untersuchen wir die Interaktion von on- und off-Zellen zur Generierung der Eingabe für eine kortikale Einfachzelle. Basierend auf physiologischen Studien schlagen wir einen Mechanismus vor, bei dem eine kortikale Einfachzelle aus beiden Domänen eine Eingabe erhält, wobei die Eingabe aus dem opponenten Pfad stärker gewichtet wird. Mit diesem Mechanismus der dominanten opponenten Inhibition können Antworten von kortikalen Einfachzellen auf Hell-Dunkel-Balken simuliert werden, die im primären visuellen Kortex der Katze gemessen wurden. Bei der Verarbeitung synthetischer und natürlicher Bilder können mit dem neuen Modell schärfere Antworten und bessere Rauschunterdrückung erreicht werden. Wir geben eine stochastische Analyse der Rauschunterdrückungscharakteristika des vorgeschlagenen Mechanismus und präsentieren detaillierte numerische Simulationen mit systematischen Parametervariationen. Die Resultate zeigen, dass das Modell kortikaler Einfachzellen mit dominanter opponenter Inhibition robuster gegenüber verrauschten Eingaben wird, weitgehend unabhängig von der Stärke des Rauschens. Diese Eigenschaft ist möglicherweise der Grund für die physiologisch gemessene dominante Inhibition und für die Repräsentation von Kontrastinformation in zwei komplementären Domänen. Basierend auf diesen Ergebnissen stellen wir die Hypothese auf, dass dominante opponente Inhibition im visuellen System verwendet wird, um in verrauschten Umgebungen Kontraste robust extrahieren zu können. Summary. In the primary visual pathway, information is represented in two distinct, complementary domains, namely "on" and "off" cells. In this work we examine how on and off cells may interact to form the input to simple cell subfields. On the basis of physiological evidence, we propose a mechanism of dominating opponent inhibition, where a simple cell subfield is driven by both on and off domains, receiving more heavily weighted input from the opponent pathway. We demonstrate that the model can account for physiological data on luminance gradient reversal recorded from simple cells in cat striate cortex. Next, we use the model for the processing of synthetic and natural images, showing that sharpness of response and robustness to noise can be increased by dominating opponent inhibition. Finally, we present a stochastic analysis of the noise-suppression characteristics of the proposed mechanism accompanied by detailed simulations with systematic parameter variations. Results show that dominating opponent inhibition makes the simple cell responses more robust to noise, largely independently of the amount of noise added. This property may give a rationale for the strong inhibition measured physiologically and for the representation of contrast information in two complementary domains. On the basis of these findings, we hypothesize that the visual system uses dominating opponent inhibition in order to robustly extract features in noisy environments.     

Incremental validity principles in test construction

The authors articulate 5 basic principles for enhancing incremental validity, both among elements within a test and between tests, during test construction: (a) careful, precise articulation of each element or facet within the content domain; (b) reliable measurement of each facet through use of multiple, alternate-form items; (c) examination of incremental validity at the facet level rather than the broad construct level; (d) use of items that represent single facets rather than combinations of facets; and (e) empirical examination of whether there is a broad construct or a combination of separate constructs. Using these principles, the authors offer specific suggestions for modifications in 3 classic test construction approaches; (a) criterion keying, (b) inductive test construction, and (c) deductive test construction. Implementation of these suggestions is likely to provide theoretical clarification and improved prediction.     

Violent children: bridging development,intervention, and public policy

Childhood violence is a major public health and social policy concern in the United States. Scientists and policymakers alike have increasingly turned their attention to the causes of childhood violence and the extent to which its course can be modified through well-planned preventive interventions. However, it is not apparent that policymakers draw upon basic research findings in formulating their priorities and policies, nor is it apparent that developmental scientists incorporate policy considerations and prevention findings into their research frameworks and designs. The goal of this special issue on violent children is to begin to bridge the gaps among basic developmental science, prevention science, and public policy.     

Developing a new quantitative account of backward masking

A new general explanation for u-shaped backward masking is analyzed and found to predict shifts in the interstimulus interval (ISI) that produces strongest masking. This predicted shift is then compared to six sets of masking data. The resulting comparisons force the general explanation to make certain assumptions to account for the data. In this way, the experimental data promote the development of a new theory of backward masking. The new theory suggests interpretations of the data that are sometimes novel, often more precise, and sometimes contrary to interpretations that are prevalent in the literature.     

The vulnerability of values to attack: inoculation of values and value-relevant attitudes

Based on the values-as-truisms hypothesis and inoculation theory, two experiments tested whether providing cognitive defenses for the value of equality induces resistance against a message attacking this value. Experiment 1 found that participants who generated cognitive support in an active-supportive or an active-refutational defense were less persuaded by a subsequent message attacking equality than were participants who engaged in no prior defense. Experiment 2 examined the effects of an active-refutational defense and a passive-refutational defense, which simply asked participants to read reasons supporting or opposing equality. Results indicated additive effects of the active and passive defenses, such that participants were most resistant to the anti-equality message when they were given both defenses. Mediational analysis across both experiments revealed that the defenses increased counterargumentation of the anti-equality message, which led to increased post-attack importance of equality and predicted more favorable equality-relevant attitudes and values.     

Adaptive self-regulation of unattainable goals: goal disengagement, goal reengagement, and subjective well-being

Three studies examined associations between goal disengagement, goal reengagement, and subjective well-being. In Study 1, 115 undergraduates reported on the extent to which they were able to abandon unattainable goals and reengage their efforts in alternative goals. Study 2 examined the importance of goal disengagement and goal reengagement in groups of young adults and older adults (N = 120). In Study 3, a sample of parents of children with cancer and parents of medically healthy children was examined (N = 45). The findings confirmed that goal disengagement and goal reengagement can be associated with ratings of high subjective well-being. In addition, the results showed that goal disengagement and goal reengagement can have interactive effects on subjective well-being. The importance of the findings for effective self-regulation and successful development are discussed.     

Paying attention to emotion: an fMRI investigation of cognitive and emotional stroop tasks

In this research, we investigated the degree to which brain systems involved in ignoring emotionally salient information differ from those involved in ignoring nonemotional information. The design allowed examination of regional brain activity, using fMRI during color-word and emotional Stroop tasks. Twelve participants indicated the color of words while ignoring word meaning in conditions in which neutral words were contrasted to emotionally negative, emotionally positive, and incongruent color words. Dorsolateral frontal lobe activity was increased by both negative and incongruent color words, indicating a common system for maintaining an attentional set in the presence of salient distractors. In posterior regions of the brain, activity depended on the nature of the information to be ignored. Ignoring color-incongruent words increased left parietal activity and decreased parahippocampal gyrus activity, whereas ignoring negative emotional words increased bilateral occipito-temporal activity and decreased amygdala activity. The results indicate that emotion and attention are intimately related via a network of regions that monitor for salient information, maintain attention on the task, suppress irrelevant information, and select appropriate responses.