The reentry hypothesis: the putative interaction of the frontal eye field, ventrolateral prefrontal cortex, and areas V4, IT for attention and eye movement

Attention is known to play a key role in perception, including action selection, object recognition and memory. Despite findings revealing competitive interactions among cell populations, attention remains difficult to explain. The central purpose of this paper is to link up a large number of findings in a single computational approach. Our simulation results suggest that attention can be well explained on a network level involving many areas of the brain. We argue that attention is an emergent phenomenon that arises from reentry and competitive interactions. We hypothesize that guided visual search requires the usage of an object-specific template in prefrontal cortex to sensitize V4 and IT cells whose preferred stimuli match the target template. This induces a feature-specific bias and provides guidance for eye movements. Prior to an eye movement, a spatially organized reentry from occulomotor centers, specifically the movement cells of the frontal eye field, occurs and modulates the gain of V4 and IT cells. The processes involved are elucidated by quantitatively comparing the time course of simulated neural activity with experimental data. Using visual search tasks as an example, we provide clear and empirically testable predictions for the participation of IT, V4 and the frontal eye field in attention. Finally, we explain a possible physiological mechanism that can lead to non-flat search slopes as the result of a slow, parallel discrimination process.     

Written and verbal information versus verbal information only for patients being discharged from acute hospital settings to home: systematic review

This article presents the results of a Cochrane review which was conducted to determine the effectiveness of providing written and verbal health information compared with verbal information only to patients being discharged from acute hospital settings to home. Only two trials met the review inclusion criteria. In both trials the participants were parents of children being discharged from hospital to home. The two outcomes measured in both trials were knowledge and satisfaction. The review confirms that providing written and verbal health information is more effective in improving knowledge and satisfaction than providing verbal information only for parents of children being discharged from hospital to home. There is no evidence of the effectiveness of the intervention in adults who provide their own care after discharge from hospital. Further research is required which involves adult patients being discharged from hospital to home, and research which measures a range of outcomes which include readmission rates, recovery times, patient/carer knowledge, complication rates, service utilization and costs (community, outpatient and inpatient), confidence in one's own care management, stress and anxiety levels, satisfaction with services provided prior to discharge, and adherence to recommended care.     

Insights into the control of attentional set in ADHD using the attentional blink paradigm

BACKGROUND: Previous work on visual selective attention in Attention Deficit Hyperactivity Disorder (ADHD) has utilised spatial search paradigms. This study compared ADHD to control children on a temporal search task using Rapid Serial Visual Presentation (RSVP). In addition, the effects of irrelevant singleton distractors on search performance were examined. METHOD: In each condition, subjects reported the identity of a red letter 'probe' in a sequence of white letters which appeared one after the other at a central fixation point. The temporal position of the probe varied from an initial target, which was distinguished by surrounding asterisks. The target was reported in addition to the probe in condition 2, but not in the baseline condition 1. In a third condition, the initial target was not reported, but one of the asterisks appeared as a colour singleton on some trials. RESULTS: All children displayed an 'attentional blink' with probe detection reduced when it appeared at close temporal relations relative to the target. This 'blink' reduced over time, and there were no group differences in the recovery of performance, although ADHD children made more errors overall. The ADHD group were also more vulnerable than controls to distraction from irrelevant singletons in condition 3. CONCLUSION: Although the basic mechanisms of selective attention were not impaired in children with ADHD, these children appeared to require more resources to execute the task and were more vulnerable to distraction by irrelevant singletons, indicating deficits in the maintenance of attentional control.     

Prioritizing new over old: an fMRI study of the preview search task

In visual search, observers can successfully ignore temporally separated distractors that are presented as a preview before onset of the search display. Previous behavioral studies have demonstrated the involvement of top-down selection mechanisms in preview search, biasing attention against the old set in favor of the more relevant new set. Using functional magnetic resonance imaging, we replicate and extend findings showing the involvement of superior and inferior parietal areas in the preview task when compared to both a relatively easy single-set search task and a more effortful full-set search task. In contrast, the effortful full-set search showed activation in the dorsolateral prefrontal cortex when compared to the single-set search, suggesting that this area is involved in rejecting additional distractors that could not be separated in time.     

Long-Term Efficacy of Atenolol for Atrioventricular Reciprocating Tachycardia in Children Less Than 5 Years Old

Atrioventricular reciprocating tachycardia (AVRT) using an accessory pathway is the most common supraventricular tachycardia observed in infancy and childhood. There is a general agreement to treat children older than 5 years who are on a potentially long-term antiarrhythmic agent with radiofrequency catheter ablation. Atenolol, a relatively long-acting and cardioselective -adrenoceptor blocker, has been used to control the various types of supraventricular tachycardia in children and adults. There are few reports on the use of atenolol in children <5 years old with AVRT. This retrospective study reports our experience in 22 children <5 years old (median age, 20 months) who received atenolol monotherapy between 1995 and 2001 for treatment of AVRT. AVRT was confirmed in 17 patients by transvenous or transesophageal electrophysiologic study and in 5 patients by documented preexcitation on electrocardiograms. In nine patients atenolol was the first antiarrhythmic drug given. In 15 of the 22 patients (68%) therapy with atenolol was considered successful. The average effective dose of atenolol in these 15 patients was 1.2 ± 0.3 mg/kg/day. During a median follow-up of 41 months (8–74 months), atenolol had been discontinued in 10 patients and no further attacks of tachycardia occurred except in 1 patient. In no case did the drug have to be withdrawn for adverse effects. In conclusion, this retrospective study shows that atenolol as a monotherapy is efficient and relatively safe in the long-term treatment of AVRT in young children. Atenolol can be recommended as a first-line treatment option for the management of AVRT in infants and young children.     

Scientific production and impact of nuclear medicine in Europe: how do we publish?

We performed a bibliometric search covering a 1-year period to evaluate the number and the scientific weight of nuclear medicine papers published from European as compared with other countries. The scientific impact of our discipline was evaluated according to the impact factor of each publication, and we also aimed to identify those countries and topics that are making the principal contributions to the development of our discipline. To this end, a search on MEDLINE (PubMed) was run to find all peer-reviewed articles published between April 2002 and May 2003, using isotope definitions as search terms. A total of 3,292 publications were identified. Of these, 650 were of no nuclear medicine interest, 229 were reviews and 82 had no country specified. In absolute numbers, Europe leads research in nuclear medicine (939 papers, 38.9%) followed by the USA (608 papers, 25.2%). Among European countries, Germany is the nation that is currently making the greatest contribution to the scientific production of nuclear medicine in Europe. Articles concerning the use of nuclear medicine in oncology account for more than one-quarter of all published nuclear medicine papers.     

搜索引擎的渐增式爬行和备份式更新模式

介绍了搜索引擎的总体结构,分析了搜索引擎中爬行器的爬行策略和网页库的更新模式。介绍了其中一种较为合理的爬行和更新模式及其实现技术,实现了渐增式地爬行高质量网页和提高网页库新鲜度的目的。     

The effects of saliency and task difficulty on visual search performance in ageing and Alzheimer's disease

We asked whether the poor performance on visual search tasks typical of patients with Alzheimer's disease (AD) is the result of a selective deficit in the ability to shift attention from item to item, or the consequence of an inefficient processing of each item within the search set. We attempted to manipulate the ease of attention shifting and item processing in a visual search task by manipulating target salience and task difficulty, respectively. Significant effects of both target saliency and task difficulty for both AD patients and age-matched controls were obtained, with the AD group displaying greater effects of both of these manipulations than the controls. This interaction remained even when the reaction time data were log-transformed to account for the overall slower reaction times of the AD group. We conclude that inefficiency in visual search tasks in AD probably represents the product of both attention shifting and target processing factors.     

Multiple visual memory phenomena in a memory search task

This paper reports evidence of the existence of multiple and distinct visual memory processes in a memory search task in which a divided field stimulus presentation was used at study (Experiments 1-3) and either a foveal (Experiments 1 and 2) or a lateralized (Experiment 3) stimulus presentation was used at test. These memory processes can be distinguished on the basis of (1) whether or not they are hemispherically organized; and (2) the locus of their underlying brain activity, as evidenced by the scalp distribution of the event-related brain potentials and by the localization of the event-related optical signal that accompany them. These memory effects are discussed in the context of visual form memory.     

Searching for nodules: what features attract attention and influence detection?

RATIONALE AND OBJECTIVES: The goal of the study was to determine whether there are certain physical features of pulmonary nodules that attract visual attention and contribute to increased recognition and detection by observers. MATERIALS AND METHODS: A series of posteroanterior chest images with solitary pulmonary nodules were searched by six radiologists as their eye-position was recorded. The signal-to-noise ratio, size, conspicuity, location, and calcification status were measured for each nodule. Dwell parameters were correlated with nodule features and related to detection rates. RESULTS: Only nodule size (F = 5.08, P = .0254) and conspicuity (F = 4.625, P = .0329) influenced total dwell time on nodules, with larger, more conspicuous nodules receiving less visual attention than smaller, less conspicuous nodules. All nodule features examined influenced overall detection performance (P < .05) even though most did not influence visual search and attention. CONCLUSION: Individual nodule features do not attract attention as measured by "first hit" fixation data, but certain features do tend to hold attention once the nodule has been fixated. The combination of all features influences whether or not it is detected.