Deafness and visual enumeration: Not all aspects of attention are modified by deafness

Previous studies have demonstrated that early deafness causes enhancements in peripheral visual attention. Here, we ask if this cross-modal plasticity of visual attention is accompanied by an increase in the number of objects that can be grasped at once. In a first experiment using an enumeration task, Deaf adult native signers and hearing nonsigners performed comparably, suggesting that deafness does not enhance the number of objects one can attend to simultaneously. In a second experiment using the Multiple Object Tracking task, Deaf adult native signers and hearing non-signers also performed comparably when required to monitor several, distinct, moving targets among moving distractors. The results of these experiments suggest that deafness does not significantly alter the ability to allocate attention to several objects at once. Thus, early deafness does not enhance all facets of visual attention, but rather its effects are quite specific. Introduction The loss of a sensory system early in development causes profound neural reorganization, and in particular an enhancement of the remaining modalities, a phenomenon also termed cross-modal plasticity One aspect of vision that has been reliably documented to be enhanced following auditory deprivation is peripheral visual processing, in particular during attentionally demanding tasks using moving stimuli. For example, deaf individuals exhibit a larger field of view than hearing controls when aske

Clusters of microRNAs emerge by new hairpins in existing transcripts

Genetic linkage may result in the expression of multiple products from a polycistronic transcript, under the control of a single promoter. In animals, protein-coding polycistronic transcripts are rare. However, microRNAs are frequently clustered in the genomes of animals, and these clusters are often transcribed as a single unit. The evolution of microRNA clusters has been the subject of much speculation, and a selective advantage of clusters of functionally related microRNAs is often proposed. However, the origin of microRNA clusters has not been so far explored. Here, we study the evolution of microRNA clusters in Drosophila melanogaster. We observed that the majority of microRNA clusters arose by the de novo formation of new microRNA-like hairpins in existing microRNA transcripts. Some clusters also emerged by tandem duplication of a single microRNA. Comparative genomics show that these clusters are unlikely to split or undergo rearrangements. We did not find any instances of clusters appearing by rearrangement of pre-existing microRNA genes. We propose a model for microRNA cluster evolution in which selection over one of the microRNAs in the cluster interferes with the evolution of the other linked microRNAs. Our analysis suggests that the study of microRNAs and small RNAs must consider linkage associations

Explicit Processing Demands Reveal Language Modality-Specific Organization of Working Memory

The working memory model for Ease of Language Understanding (ELU) predicts that processing differences between language modalities emerge when cognitive demands are explicit. This prediction was tested in three working memory experiments with participants who were Deaf Signers (DS), Hearing Signers (HS), or Hearing Nonsigners (HN). Easily nameable pictures were used as stimuli to avoid confounds relating to sensory modality. Performance was largely similar for DS, HS, and HN, suggesting that previously identified intermodal differences may be due to differences in retention of sensory information. When explicit processing demands were high, differences emerged between DS and HN, suggesting that although working memory storage in both groups is sensitive to temporal organization, retrieval is not sensitive to temporal organization in DS. A general effect of semantic similarity was also found. These findings are discussed in relation to the ELU model

Deaf children's non-verbal working memory is impacted by their language experience

Several recent studies have suggested that deaf children perform more poorly on working memory tasks compared to hearing children, but these studies have not been able to determine whether this poorer performance arises directly from deafness itself or from deaf children's reduced language exposure. The issue remains unresolved because findings come mostly from (1) tasks that are verbal as opposed to non-verbal, and (2) involve deaf children who use spoken communication and therefore may have experienced impoverished input and delayed language acquisition. This is in contrast to deaf children who have been exposed to a sign language since birth from Deaf parents (and who therefore have native language-learning opportunities within a normal developmental timeframe for language acquisition). A more direct, and therefore stronger, test of the hypothesis that the type and quality of language exposure impact working memory is to use measures of non-verbal working memory (NVWM) and to compare hearing children with two groups of deaf signing children: those who have had native exposure to a sign language, and those who have experienced delayed acquisition and reduced quality of language input compared to their native-signing peers. In this study we investigated the relationship between NVWM and language in three groups aged 6–11 years: hearing children (n = 28), deaf children who were native users of British Sign Language (BSL; n = 8), and deaf children who used BSL but who were not native signers (n = 19). We administered a battery of non-verbal reasoning, NVWM, and language tasks. We examined whether the groups differed on NVWM scores, and whether scores on language tasks predicted scores on NVWM tasks. For the two executive-loaded NVWM tasks included in our battery, the non-native signers performed less accurately than the native signer and hearing groups (who did not differ from one another). Multiple regression analysis revealed that scores on the vocabulary measure predicted scores on those two executive-loaded NVWM tasks (with age and non-verbal reasoning partialled out). Our results suggest that whatever the language modality—spoken or signed—rich language experience from birth, and the good language skills that result from this early age of acquisition, play a critical role in the development of NVWM and in performance on NVWM tasks

Prediction of novel microRNA genes in cancer-associated genomic regions—a combined computational and experimental approach

The majority of existing computational tools rely on sequence homology and/or structural similarity to identify novel microRNA (miRNA) genes. Recently supervised algorithms are utilized to address this problem, taking into account sequence, structure and comparative genomics information. In most of these studies miRNA gene predictions are rarely supported by experimental evidence and prediction accuracy remains uncertain. In this work we present a new computational tool (SSCprofiler) utilizing a probabilistic method based on Profile Hidden Markov Models to predict novel miRNA precursors. Via the simultaneous integration of biological features such as sequence, structure and conservation, SSCprofiler achieves a performance accuracy of 88.95% sensitivity and 84.16% specificity on a large set of human miRNA genes. The trained classifier is used to identify novel miRNA gene candidates located within cancer-associated genomic regions and rank the resulting predictions using expression information from a full genome tiling array. Finally, four of the top scoring predictions are verified experimentally using northern blot analysis. Our work combines both analytical and experimental techniques to show that SSCprofiler is a highly accurate tool which can be used to identify novel miRNA gene candidates in the human genome. SSCprofiler is freely available as a web service at http://www.imbb.forth.gr/SSCprofiler.html

MicroRNA: an Emerging Therapeutic Target and Intervention Tool

MicroRNAs (miRNAs) are a class of short non-coding RNAs with posttranscriptional regulatory functions. To date, more than 600 human miRNAs have been experimentally identified, and estimated to regulate more than one third of cellular messenger RNAs. Accumulating evidence has linked the dysregulated expression patterns of miRNAs to a variety of diseases, such as cancer, neurodegenerative diseases, cardiovascular diseases and viral infections. MiRNAs provide its particular layer of network for gene regulation, thus possessing the great potential both as a novel class of therapeutic targets and as a powerful intervention tool. In this regard, synthetic RNAs that contain the binding sites of miRNA have been shown to work as a “decoy” or “miRNA sponge” to inhibit the function of specific miRNAs. On the other hand, miRNA expression vectors have been used to restore or overexpress specific miRNAs to achieve a long-term effect. Further, double-stranded miRNA mimetics for transient replacement have been experimentally validated. Endogenous precursor miRNAs have also been used as scaffolds for the induction of RNA interference. This article reviews the recent progress on this emerging technology as a powerful tool for gene regulation studies and particularly as a rationale strategy for design of therapeutics