The Role of Semantic Representations in Verbal Working Memory

Two main mechanisms, articulatory rehearsal and attentional refreshing, are argued to be involved in the maintenance of verbal information in working memory (WM). While converging research has suggested that rehearsal promotes the phonological representations of memoranda in working memory, little is known about the representations that refreshing may promote. Not only would examining this question address this gap in the literature, but the investigation has profound implications for different theoretical proposals of how refreshing functions and on the relationships between WM and long-term memory (LTM). Accordingly, we tested predictions from five models regarding how refreshing may moderate the semantic representation of memoranda in verbal WM. This series of four experiments presented a cue word that was either semantically or phonologically related to a target during the recall phase of a complex span task. Experiment 1 established the benefit of semantic over phonological retrieval cues, and Experiment 2 established that this semantic benefit was specific to a refreshing- rather than a rehearsal-based maintenance strategy. Finally, we showed that this semantic benefit did not vary with the cognitive load of the concurrent task (Experiments 3 and 4) or the intention to learn the memoranda (Experiment 4). These results indicate that cue-based retrieval from episodic LTM may strongly contribute to semantic processing effects in WM recall, but this influence of episodic LTM is independent of the function of refreshing to reactivate memory traces. Accordingly, these results have strong implications for the functioning of refreshing and the links between WM and LTM

Magnetic characterization of Fe, Ni, Co nanoparticles dispersed in phyllosilicate type silicon oxide

International audienceWe present the magnetic properties of silica-supported metal (Fe,catalyst) nanoparticles synthesized by precipitation of metal nitrate in ammonia-based medium. Our goal is the study of possible metal-support interactions in the nanoporous catalyst. The temperature dependence of the magnetization for all samples display spin-glass like behavior below c.a. 11-12 K, with clear Curie-Weiss dependence in the high-temperature regime. Spin-glass-like behavior was inferred from dynamic AC susceptibility data after analyzing the frequency-dependence of the in-phase component χ'(f) by the expression W = ΔTf/[Tf Δlog(f)] = 3.0 × 10−3. We found that the magnetic behavior of the catalyst is drastically affected by the existence of interactions between the metal and the support

Utilizing optical transition edge sensors and superconducting nanowire single photon detectors in quantum optics

We present the current state-of-the art of single-photon detection in quantum optics using high-efficiency superconducting single photon detectors, the implementation of highefficiency sources and the measurement of large photon number squeezing in waveguides

Are latent working memory items retrieved from long-term memory?

Switching one’s focus of attention between to-be-remembered items in working memory (WM) is critical for cognition, but the mechanisms by which this is accomplished are unclear. A long-term memory (LTM) account suggests that switching attention away from an item, and passively retaining and reactivating such “latent” items back into the focus of attention involves episodic LTM retrieval processes, even for delays of only a few seconds. We tested this hypothesis using a two-item, double-retrocue WM task that requires participants to switch attention away from and reactivate items followed by subsequent LTM tests for reactivated items from the initial WM task (vs. continuously retained or untested control items). We compared performance on these tests between older adults (a population with LTM deficits) and young adults with either full (Experiment 1) or divided (Experiment 2) attention during the WM delay periods. The effects of reactivating latent items, as well as ageing and divided attention, had significant effects on WM performance, but did not interact with or systematically affect subsequent LTM for reactivated versus control items on item-, location-, or associative-recognition memory judgements made with either high or low confidence. Experiment 3 confirmed that these effects did not depend on whether or not young participants were warned about the subsequent LTM tests before performing the WM task. These dissociations between WM and LTM are inconsistent with the LTM account of latent WM; they are more consistent with the dynamic processing model of WM (Current Directions in Psychological Science)

Software en tiempo real para el analisis de sistemas sonoros

The two-way sound systems require time alignment procedures between different speakers using audio processors. Framed in this object of study, this article describes the implementation of a software tool for the analysis of sound systems. This tool was developed in the visual programming environment Matlab ®, Simulink ®, and is useful for evaluating the performance of a sound in an enclosure through the analysis of the frequency response of the same, which is affected by the acoustics of the room. Tests show that the software is reliable, presenting relative errors less than 4% in the different modes of operation.Los sistemas sonoros a dos vías requieren procedimientos de alineación de tiempo entre las diferentes cajas acústicas, usando procesadores de audio. Enmarcado en este objeto de estudio, el presente artículo describe la implementación de una herramienta software para el análisis de sistemas sonoros. Esta herramienta fue desarrollada en el entorno de programación visual de Matlab®, Simulink®, y es de gran utilidad para evaluar el desempeño de un equipo de sonido en un recinto mediante el análisis de su respuesta en frecuencia, la cual es afectada por la acústica del local. Las pruebas demuestran que el software es confiable y que presenta errores relativos inferiores al 4% en los diferentes modos de operación

Exact solutions in a scalar-tensor model of dark energy

We consider a model of scalar field with non minimal kinetic and Gauss Bonnet couplings as a source of dark energy. Based on asymptotic limits of the generalized Friedmann equation, we impose restrictions on the kinetic an Gauss-Bonnet couplings. This restrictions considerable simplify the equations, allowing for exact solutions unifying early time matter dominance with transitions to late time quintessence and phantom phases. The stability of the solutions in absence of matter has been studied.Comment: 30 pages, 2 figures, to appear in JCA

Single-cell profiling of human megakaryocyte-erythroid progenitors identifies distinct megakaryocyte and erythroid differentiation pathways

Background Recent advances in single-cell techniques have provided the opportunity to finely dissect cellular heterogeneity within populations previously defined by “bulk” assays and to uncover rare cell types. In human hematopoiesis, megakaryocytes and erythroid cells differentiate from a shared precursor, the megakaryocyte-erythroid progenitor (MEP), which remains poorly defined. Results To clarify the cellular pathway in erythro-megakaryocyte differentiation, we correlate the surface immunophenotype, transcriptional profile, and differentiation potential of individual MEP cells. Highly purified, single MEP cells were analyzed using index fluorescence-activated cell sorting and parallel targeted transcriptional profiling of the same cells was performed using a specifically designed panel of genes. Differentiation potential was tested in novel, single-cell differentiation assays. Our results demonstrate that immunophenotypic MEP comprise three distinct subpopulations: “Pre-MEP,” enriched for erythroid/megakaryocyte progenitors but with residual myeloid differentiation capacity; “E-MEP,” strongly biased towards erythroid differentiation; and “MK-MEP,” a previously undescribed, rare population of cells that are bipotent but primarily generate megakaryocytic progeny. Therefore, conventionally defined MEP are a mixed population, as a minority give rise to mixed-lineage colonies while the majority of cells are transcriptionally primed to generate exclusively single-lineage output. Conclusions Our study clarifies the cellular hierarchy in human megakaryocyte/erythroid lineage commitment and highlights the importance of using a combination of single-cell approaches to dissect cellular heterogeneity and identify rare cell types within a population. We present a novel immunophenotyping strategy that enables the prospective identification of specific intermediate progenitor populations in erythro-megakaryopoiesis, allowing for in-depth study of disorders including inherited cytopenias, myeloproliferative disorders, and erythromegakaryocytic leukemias