The effects of task complexity and practice on dual-task interference in visuospatial working memory

Although the n-back task has been widely applied to neuroimagery investigations of working memory (WM), the role of practice effects on behavioural performance of this task has not yet been investigated. The current study aimed to investigate the effects of task complexity and familiarity on the n-back task. Seventy-seven participants (39 male, 38 female) completed a visuospatial n-back task four times, twice in two testing sessions separated by a week. Participants were required to remember either the first, second or third (n-back) most recent letter positions in a continuous sequence and to indicate whether the current item matched or did not match the remembered position. A control task, with no working memory requirements required participants to match to a predetermined stimulus position. In both testing sessions, reaction time (RT) and error rate increased with increasing WM load. An exponential slope for RTs in the first session indicated dual-task interference at the 3-back level. However, a linear slope in the second session indicated a reduction of dual-task interference. Attenuation of interference in the second session suggested a reduction in executive demands of the task with practice. This suggested that practice effects occur within the n-back ask and need to be controlled for in future neuroimagery research using the task.

The complexity of drinking: Interactions between the cognitive and behavioural determinants of alcohol consumption

This study expanded the earlier work conducted by this laboratory ( Hasking, P.A. and Oei, T.P.S. (2002a) . The differential role of alcohol expectancies, drinking refusal self-efficacy and coping resources in predicting alcohol consumption in community and clinical samples. Addiction Research and Theory , 10 , 465-494), by examining the independent and interactive effects of avoidant coping strategies, positive and negative expectancies and self-efficacy, in predicting volume and frequency of alcohol consumption in a sample of community drinkers. Differential relationships were found between the variables when predicting the two consumption measures. Specifically, while self-efficacy, seeking social support for emotional reasons and using drugs or alcohol to cope were independently related to both volume and frequency of drinking, complex interactions with positive and negative alcohol expectancies were also found. These interactions are discussed in terms of the cognitive and behavioural mechanisms thought to underlie drinking behaviour.

Comorbidity: Cannabis and complexity

Cannabis is one of the most commonly used illicit drugs, and its effects have traditionally been seen as less harmful than outcomes associated with the highly prevalent use of alcohol and other illicit substances (e.g., cocaine and amphetamines), and injecting drugs. Consequently, less attention has been focused on developing and evaluating interventions in this area. However, current research supports the idea that cannabis does pose a number of acute and chronic health risks to the individual and to society. The authors review findings concerning the physiological and neurological effects of cannabis, prevalence of use, and studies concerning its possible role as a "gateway" drug. Diagnostic criteria for cannabis dependence and abuse are discussed, with a focus on whether a cannabis withdrawal syndrome exists and if so how it can be diagnosed. There is strong support for a link between cannabis and the development and exacerbation of psychosis and other mental health conditions (e.g., anxiety, depression). Further research is needed to determine the underlying neurochemical processes and their possible contribution to etiology, as well as the social factors that contribute to the increasing use of cannabis by young people. In addition there is a need for systematic evaluation using randomized controlled trials to determine effective prevention and treatment strategies. A number of public health programs that address cannabis use are reviewed along with available evidence for their effectiveness.

Syntactic complexity measures and their relation to oral proficiency in Japanese as a foreign language

The study reported in this article is a part of a large-scale study investigating syntactic complexity in second language (L2) oral data in commonly taught foreign languages (English, German, Japanese, and Spanish; Ortega, Iwashita, Rabie, & Norris, in preparation). In this article, preliminary findings of the analysis of the Japanese data are reported. Syntactic complexity, which is referred to as syntactic maturity or the use of a range of forms with degrees of sophistication (Ortega, 2003), has long been of interest to researchers in L2 writing. In L2 speaking, researchers have examined syntactic complexity in learner speech in the context of pedagogic intervention (e.g., task type, planning time) and the validation of rating scales. In these studies complexity is examined using measures commonly employed in L2 writing studies. It is assumed that these measures are valid and reliable, but few studies explain what syntactic complexity measures actually examine. The language studied is predominantly English, and little is known about whether the findings of such studies can be applied to languages that are typologically different from English. This study examines how syntactic complexity measures relate to oral proficiency in Japanese as a foreign language. An in-depth analysis of speech samples from 33 learners of Japanese is presented. The results of the analysis are compared across proficiency levels and cross-referenced with 3 other proficiency measures used in the study. As in past studies, the length of T-units and the number of clauses per T-unit is found to be the best way to predict learner proficiency; the measure also had a significant linear relation with independent oral proficiency measures. These results are discussed in light of the notion of syntactic complexity and the interfaces between second language acquisition and language testing. Adapted from the source document

An analysis of relational complexity in an air traffic control conflict detection task

Theoretical analyses of air traffic complexity were carried out using the Method for the Analysis of Relational Complexity. Twenty-two air traffic controllers examined static air traffic displays and were required to detect and resolve conflicts. Objective measures of performance included conflict detection time and accuracy. Subjective perceptions of mental workload were assessed by a complexity-sorting task and subjective ratings of the difficulty of different aspects of the task. A metric quantifying the complexity of pair-wise relations among aircraft was able to account for a substantial portion of the variance in the perceived complexity and difficulty of conflict detection problems, as well as reaction time. Other variables that influenced performance included the mean minimum separation between aircraft pairs and the amount of time that aircraft spent in conflict.

Cyclic MrIA: A stable and potent cyclic conotoxin with a novel topological fold that targets the norepinephrine transporter

Conotoxins, disulfide-rich peptides from the venom of cone snails, have created much excitement over recent years due to their potency and specificity for ion channels and their therapeutic potential. One recently identified conotoxin, MrIA, a 13-residue member of the chi-conotoxin family, inhibits the human norepinephrine transporter (NET) and has potential applications in the treatment of pain. In the current study, we show that the, beta-hairpin structure of native MrIA is retained in a synthetic cyclic version, as is biological activity at the NET. Furthermore, the cyclic version has increased resistance to trypsin digestion relative to the native peptide, an intriguing result because the cleavage site for the trypsin is not close to the cyclization site. The use of peptides as drugs is generally hampered by susceptibility to proteolysis, and so, the increase in enzymatic stability against trypsin observed in the current study may be useful in improving the therapeutic potential of MrIA. Furthermore, the structure reported here for cyclic MrIA represents a new topology among a growing number of circular disulfide-rich peptides.

Phosphoinositide regulation of neuroexocytosis: adding to the complexity

Exocytosis of neurotransmitter containing vesicles supports neuronal communication. The importance of molecular interactions involving specific lipids has become progressively more evident and the lipid composition of both the synaptic vesicle and the pre-synaptic plasma membrane at the active zone has significant functional consequences for neurotransmitter release. Several classes of lipids have been implicated in exocytosis including polyunsaturated fatty acids and phosphoinositides. This minireview will focus on recent developments regarding the role of phosphoinositides in neurosecretion.

Summarizing level-two topological relations in large spatial datasets

Summarizing topological relations is fundamental to many spatial applications including spatial query optimization. In this article, we present several novel techniques to effectively construct cell density based spatial histograms for range (window) summarizations restricted to the four most important level-two topological relations: contains, contained, overlap, and disjoint. We first present a novel framework to construct a multiscale Euler histogram in 2D space with the guarantee of the exact summarization results for aligned windows in constant time. To minimize the storage space in such a multiscale Euler histogram, an approximate algorithm with the approximate ratio 19/12 is presented, while the problem is shown NP-hard generally. To conform to a limited storage space where a multiscale histogram may be allowed to have only k Euler histograms, an effective algorithm is presented to construct multiscale histograms to achieve high accuracy in approximately summarizing aligned windows. Then, we present a new approximate algorithm to query an Euler histogram that cannot guarantee the exact answers; it runs in constant time. We also investigate the problem of nonaligned windows and the problem of effectively partitioning the data space to support nonaligned window queries. Finally, we extend our techniques to 3D space. Our extensive experiments against both synthetic and real world datasets demonstrate that the approximate multiscale histogram techniques may improve the accuracy of the existing techniques by several orders of magnitude while retaining the cost efficiency, and the exact multiscale histogram technique requires only a storage space linearly proportional to the number of cells for many popular real datasets.

The complexity of p53 stabilization and activation

A number of proteins are activated by stress stimuli but none so spectacularly or with the degree of complexity as the tumour suppressor p53 (human p53 gene or protein). Once stabilized, p53 is responsible for the transcriptional activation of a series of proteins involved in cell cycle control, apoptosis and senescence. This protein is present at low levels in resting cells but after exposure to DNA-damaging agents and other stress stimuli it is stabilized and activated by a series of post-translational modifications that free it from MDM2 (mouse double minute 2 but used interchangeably to denote human also), a ubiquination ligase that ubiquitinates it prior to proteasome degradation. The stability of p53 is also influenced by a series of other interacting proteins. In this review, we discuss the post-translational modifications to p53 in response to different stresses and the consequences of these changes.