Memory Set Research Articles

Dignity Therapy and Life Review for Palliative Care Patients: A Qualitative Study

ContextDignity therapy (DT) is a psychotherapeutic intervention whose aim was to bolster the sense of purpose, meaning, and sense of dignity in patients with terminal disease. ObjectivesThe aim of this study was to explore, compare, and better understand the content of standard DT, waitlist DT (WDT), and Life Review (LR) that used the DT interview protocol but omitted the creation of legacy documents. MethodsEfficacy of these interventions was previously documented in a sample of 56 participants. In this study, DT and WDT legacy documents and LR session transcripts were qualitatively analyzed using the Framework approach, both deductively and inductively. ResultsAll participants expressed a diverse set of beliefs, values, memories, and important relationships with the majority also indicating at least some sense of meaning and acceptance despite disappointments, regrets, and the impacts of illness. Sense of legacy, fighting spirit, and hope were particularly prevalent in legacy documents (DT and WDT groups), whereas relationship regrets, self-blame, unfinished business, and aftermath concerns were more likely to be expressed during the LR process. Themes of spirituality, illness impacts, and unfinished business were relatively less common in WDT participants. ConclusionThis study provides further insight into what palliative care patients consider to be most important and meaningful to them when taking part in DT and LR. Creating legacy documents is likely to result in session content that is different in several key areas compared with LR, even when controlling for interview questions, therapist influences, and session length. Consideration of the above is essential in optimizing psychotherapeutic outcomes near end of life.

Hierarchical Bayesian measurement models for continuous reproduction of visual features from working memory.

The article presents Bayesian hierarchical modeling frameworks for two measurement models for visual working memory. The models can be applied to the distributions of responses on a circular feature dimension, as obtained with the continuous reproduction (a.k.a. delayed estimation) task. The first measurement model is a mixture model that describes the response distributions as a mixture of one (Zhang & Luck, 2008) or several (Bays, Catalao, & Husain, 2009) von-Mises distribution(s) and a uniform distribution. The second model is a novel, interference-based measurement model. We present parameter recovery simulations for both models, demonstrating that the hierarchical framework enables precise parameter estimates when a small number of trials are compensated by a large number of subjects. Simulations with the mixture model show that the Bayesian hierarchical framework minimizes the previously observed estimation bias for memory precision in conditions of low performance. Unbiased and reasonably precise parameter estimates can also be obtained from the interference measurement model, though some parameters of this model demand a relatively large amount of data for precise measurement. Both models are applied to two experimental data sets. Experiment 1 measures the effect of memory set size on the model parameters. Experiment 2 provides evidence for the assumption in the interference model that the target feature tends to be confused with features of those nontargets that are close to the target on the dimension used as retrieval cue.

Dispositivos de informação: arquivos, memórias e informação

Resumo O artigo aborda as dinâmicas do fenômeno informação como instrumento de desenvolvimento das lógicas e dos valores presentes nos quadros da memória, construídos e geridos no interior dos espaços arquivísticos. Para tanto, este estudo privilegia a noção de “dispositivo” tal como elaborada na obra de Michel Foucault e uma de suas derivações como os “dispositivos de informação”, além ainda das concepções filosóficas e sociológicas sobre a memória social e o arquivo. Os conceitos e as noções empregadas são desenvolvidos em uma perspectiva privilegiada da inter-relação entre Ciência da Informação, Filosofia e Ciências Sociais, permitindo perceber que o movimento entre a informação, os arquivos e as memórias, quando ativado no interior desses “dispositivos”, delineia tipos específicos de saber, poder e sujeitos submetidos a contextos sociais, políticos e econômicos específicos. Conclui-se ao fim que a memória coletiva constitui-se como um “dispositivo” composto de discursos de verdade, apresentado na condição de arquivo, isto é, como conjunto de regras que facultam o emergir, em uma determinada época, de um tipo de discurso capaz de agir sobre os homens, tornando-os sujeitos de certo conjunto de memórias.

Introduction to the Special Issue on Practical Aspects of High-Level Parallel Programming

From smartphones to supercomputers, parallel architectures are nowadays pervasive. However parallel programming is still reserved to experienced and trained programmers. The trend is towards the increase of cores in processors and the number of processors in multiprocessor machines: The need for scalable computing is everywhere. But parallel and distributed programming is still dominated by low-level techniques such as send/receive message passing and POSIX threads. Thus high-level approaches should play a key role in the shift to scalable computing in every computer and device. Algorithmic skeletons (Google MapReduce being the most well-known skeletal parallelism approach), parallel extensions of functional languages such as Haskell and ML, parallel logic and constraint programming, parallel execution of declarative programs such as SQL queries, meta-programming in object-oriented languages, etc. have produced methods and tools that improve the price/performance ratio of parallel software, and broaden the range of target applications. Also, high level languages offer a high degree of abstraction which ease the development of complex systems. Moreover, being based on formal semantics, it is possible to certify the correctness of critical parts of the applications. The aim of all these languages and tools is to improve and ease the development of applications. The paper presented in this special issue are extended versions of papers presented at the Practical Aspects of High-Level Parallel Programming (PAPP) workshop that was affiliated to the International Conference on Computational Science (ICCS) from 2004 to 2012, and the Practical Aspects of High-Level Parallel Programming (PAPP) track of the ACM Symposium on Applied Computing (SAC). It also features a paper written specifically for this special issue. While a lot of work in high-level approaches focus on regular data structures such as arrays and multi-dimensional arrays, the papers of this issue consider more irregular data structures, in particular trees and graphs. Kaheki, Matsuzaki and Emoto present a new approach for parallel reduction on trees in a distributed memory setting. Their algorithm is based on a suitable serialization of trees and its efficiency is shown for the Bulk Synchronous Parallel (BSP) model. Matzusaki proposes a set of efficient skeletons on distributed trees: their efficient implementation relies on the segmentation of trees based on the idea of m-bridges that ensures high locality, and allows to represent local segments as serialized arrays for high sequential performance. Dazzi, Carlini, Lulli and Ricci propose Telos, a high-level approach for large graphs processing based on overlay networks, and an implementation on top of Apache Spark. Hajibaba, Gorgin, and Sharifi present a sequence similarity parallelization technique in the context of another Apache project: Storm a stream processing framework. I wish to thank Anne Benoit and Frederic Gava, co-chairs of some the previous PAPP workshops and the program committee members of the PAPP workshops and the PAPP ACM SAC track who reviewed the initial papers and the revised versions of this special issue.

Simplified SEE Sensitivity Screening for COTS Components in Space

We introduce an approach aimed at prescreening COTS components according to their single-event effect (SEE) sensitivity for space missions in which a complete characterization of their individual response to protons and heavy ions is not feasible due to cost and time constraints. The method is applied to a set of SRAM memories for single-event upset (SEU) and single-event latchup (SEL) and the resulting expected SEE rates are compared with traditional approaches and in-flight data for a low-earth orbit polar and a geostationary orbit. Despite the limitations related to components with high-LET threshold and thick sensitive volumes, we conclude that the proposed method can be an efficient means of rejecting highly sensitive components or lots and performing the complete characterization only on passing devices.

The Influence of Working Memory Load on Expectancy-Based Strategic Processes in the Stroop-Priming Task.

The present study investigated whether a differential availability of cognitive control resources as a result of varying working memory (WM) load could affect the capacity for expectancy-based strategic actions. Participants performed a Stroop-priming task in which a prime word (GREEN or RED) was followed by a colored target (red vs. green) that participants had to identify. The prime was incongruent or congruent with the target color on 80 and 20% of the trials, respectively, and participants were informed about the differential proportion of congruent vs. incongruent trials. This task was interleaved with a WM task, such that the prime word was preceded by a sequence of either a same digit repeated five times (low load) or five different random digits (high load), which should be retained by participants. After two, three, or four Stroop trials, they had to decide whether or not a probe digit was a part of the memory set. The key finding was a significant interaction between prime-target congruency and WM load: Whereas a strategy-dependent (reversed Stroop) effect was found under low WM load, a standard Stroop interference effect was observed under high WM load. These findings demonstrate that the availability of WM is crucial for implementing expectancy-based strategic actions.

Transistency Models: Memory Ordering at the Hardware-OS Interface

This article introduces the transistency model, a set of memory ordering rules at the intersection of virtual-to-physical address translation and memory consistency models. Using their COATCheck tool, the authors show how to rigorously model, analyze, and verify the correctness of a given system's microarchitecture and software stack with respect to its transistency model specification.

Transistency Models: Memory Ordering at the Hardware-OS Interface

This article introduces the transistency model, a set of memory ordering rules at the intersection of virtual-to-physical address translation and memory consistency models. Using their COATCheck tool, the authors show how to rigorously model, analyze, and verify the correctness of a given system's microarchitecture and software stack with respect to its transistency model specification.

Preventing Neurodegenerative Memory Loss in Hopfield Neuronal Networks Using Cerebral Organoids or External Microelectronics.

Developing technologies have made significant progress towards linking the brain with brain-machine interfaces (BMIs) which have the potential to aid damaged brains to perform their original motor and cognitive functions. We consider the viability of such devices for mitigating the deleterious effects of memory loss that is induced by neurodegenerative diseases and/or traumatic brain injury (TBI). Our computational study considers the widely used Hopfield network, an autoassociative memory model in which neurons converge to a stable state pattern after receiving an input resembling the given memory. In this study, we connect an auxiliary network of neurons, which models the BMI device, to the original Hopfield network and train it to converge to its own auxiliary memory patterns. Injuries to the original Hopfield memory network, induced through neurodegeneration, for instance, can then be analyzed with the goal of evaluating the ability of the BMI to aid in memory retrieval tasks. Dense connectivity between the auxiliary and Hopfield networks is shown to promote robustness of memory retrieval tasks for both optimal and nonoptimal memory sets. Our computations estimate damage levels and parameter ranges for which full or partial memory recovery is achievable, providing a starting point for novel therapeutic strategies.

Rehearsal of to-be-remembered items is unnecessary to perform directed forgetting within working memory: Support for an active control mechanism.

Directed forgetting tasks instruct people to forget targeted memoranda. In the context of working memory, people attempt to forget representations that are currently held in mind. Here, we evaluated candidate mechanisms of directed forgetting within working memory, by (a) testing the influence of articulatory suppression, a rehearsal-reducing and attention-demanding secondary task, on directed forgetting efficacy, and by (b) assessing the ability of people to perform forgetting in the absence of to-be-remembered competitors to rehearse. In Experiment 1, articulatory suppression interfered with directed forgetting, increasing the proportion of false alarms to to-be-forgotten probes in the working memory phase and decreasing the magnitude of the directed forgetting effect as assessed by an incidental long-term memory recognition test. Experiment 2 replicated the effects of articulatory suppression and tested whether the simultaneous requirement to retain, and presumably rehearse, to-be-remembered items was necessary for successful forgetting. The long-term directed forgetting effect was equivalent whether or not participants had to-be-remembered items to rehearse during the working memory phase. Experiment 3 included an additional comparison condition and confirmed that articulatory suppression interfered with directed forgetting and that participants were as efficient at directed forgetting with and without competitors to remember. In combination, these experiments suggest that directed forgetting in working memory requires an active control process that is limited by articulatory suppression, and that the demand to remember a concurrent memory set is unnecessary for this control process to operate. (PsycINFO Database Record

Dissociating models of visual working memory by reaction-time distribution analysis

There have been heated debates on whether visual working memory (VWM) represents information in discrete-slots or a reservoir of flexible-resources. However, one key aspect of the models has gone unnoticed, the speed of processing when stored information in memory is assessed for accuracy. The present study evaluated contrasting predictions from the two models regarding the change detection decision times spent on the assessment of stored information by estimating the ex-Gaussian parameters from change detection RT distributions across different set sizes (2, 4, 6, or 8). The estimation showed that the Gaussian components μ and σ became larger as the set size increased from 2 to 4, but stayed constant as it reached 6 and 8, with an exponential component τ increasing at above-capacity set sizes. Moreover, we found that an individual's capacity limit correlates with the memory set size where the Gaussian μ reaches a plateau. These results indicate that the decision time for assessing in-memory items is constant regardless of memory set sizes whereas the time for the remaining not-in-memory items increases as the set size exceeds VWM storage capacity. The findings suggest that the discrete-slot model explains the observed RT distributions better than the flexible-resource model.

Popular Cultural Memory in Chris Abani’s Graceland

This essay argues that Chris Abani’s Graceland uses popular culture as a project of narrative memory. This project of memory involves the performance of popular expressive cultures across a range of mediated texts — literary and musical — within the context of the everyday. The paper also argues that Abani’s recourse, particularly to Onitsha Market Literature, gives the text the dimension of a literary archive of urban cultural history, especially the history of literacy in Lagos. Abani re-animates Onitsha Market literary history as foundational of Lagosian cultural memory. The manner of its invocation allows Graceland to be a textual archive of the metropolis while creating sensorial cartographies of Lagos through the flaneur figure of its protagonist, Elvis Oke. Abani’s narrative project seems to not only be a performative site of a particular set of entangled memories, but also to work through memorial artefacts — texts, books and other cultural products. In effect, Graceland performs its own materiality within the narrative(s) of memory that enables its existence.

Causal-consistent rollback in a tuple-based language

Rollback is a fundamental technique for ensuring reliability of systems, allowing one, in case of troubles, to recover a past system state. However, the definition of rollback in a concurrent/distributed scenario is quite tricky. We propose an approach based on the notion of causal-consistent reversibility: any given past action can be undone, provided that all the actions caused by it are undone as well. Given that, we define a rollback as the minimal causal-consistent sequence of backward steps able to undo a given action. We define the semantics of such a rollback operator, and show that it satisfies the above specification. The approach that we present is quite general, but we instantiate it in the case of μKlaim, a formal coordination language based on distributed tuple spaces. We remark that this is the first definition of causal-consistent rollback in a shared–memory setting. We illustrate the use of rollback in μKlaim on a simple, but realistic, application scenario.

Dynamic Organization of Hierarchical Memories

In the brain, external objects are categorized in a hierarchical way. Although it is widely accepted that objects are represented as static attractors in neural state space, this view does not take account interaction between intrinsic neural dynamics and external input, which is essential to understand how neural system responds to inputs. Indeed, structured spontaneous neural activity without external inputs is known to exist, and its relationship with evoked activities is discussed. Then, how categorical representation is embedded into the spontaneous and evoked activities has to be uncovered. To address this question, we studied bifurcation process with increasing input after hierarchically clustered associative memories are learned. We found a “dynamic categorization”; neural activity without input wanders globally over the state space including all memories. Then with the increase of input strength, diffuse representation of higher category exhibits transitions to focused ones specific to each object. The hierarchy of memories is embedded in the transition probability from one memory to another during the spontaneous dynamics. With increased input strength, neural activity wanders over a narrower state space including a smaller set of memories, showing more specific category or memory corresponding to the applied input. Moreover, such coarse-to-fine transitions are also observed temporally during transient process under constant input, which agrees with experimental findings in the temporal cortex. These results suggest the hierarchy emerging through interaction with an external input underlies hierarchy during transient process, as well as in the spontaneous activity.

(Invited) Bipolar Switching of Phase Change Memory for Enhanced High-Temperature Stability

Phase change memory (PCM) devices are among the most mature technology for storage class memory and embedded memory for, e.g., the internet of things (IoT). One of the key limitation of PCM is the crystallization of the amorphous phase taking place at relatively low temperature, e.g., 150°C for Ge2Sb2Te5(GST) [1]. The low crystallization point prevents the use of PCM in high-temperature applications, such as automotive and embedded chips requiring retention up to 260°C. To overcome the temperature limitations, phase change materials with higher stability against crystallization have been presented, such as C-doped GST [2] and Ge-rich GST [3]. However, increasing the crystallization point raises stability issues for the set (crystalline) state due to the time evolution of the grain boundary structure [4]. Therefore, other techniques to improve the high-temperature reliability of PCM, e.g., by algorithm and/or alternative storage concepts, must be developed.This work addresses the bipolar switching of PCM. Mushroom-type devices with confined bottom electrode (or heater), where subjected to bipolar operation: the application of a positive voltage to a PCM in the amorphous phase leads to threshold switching and set transition to low resistance, while the application of a negative voltage causes a reset transition to high resistance, similar to the one typically observed in resistive switching memory (RRAM). The reset voltage is lower than the melting temperature, thus evidencing that reset transition is not due to a phase change, such as melting and amorphization. Bipolar switching is interpreted by ionic migration of elemental species, such as Ge, Sb and Te in GST. The initial positive voltage causes crystallization with approximately uniform distribution of atomic elements, then the applied negative voltage causes ionic migration driven by the electric field and accelerated by the local Joule heating. In particular, cation-type Ge and Sb migrate toward the top electrode, thus leaving a depleted region in correspondence of the bottom electrode. The high concentration of vacancies and possibly microvoids in the depleted region are responsible for the high resistance which can reach the few GΩ range. Application of a positive voltage results in ionic redistribution and the decrease of resistance. The stability of the bipolar reset state was addressed at both room temperature and high temperature. The bipolar reset state does not show any resistance drift, confirming that the storage concept does not rely on the transition to the amorphous phase. Similarly, there is no evidence for crystallization at high-temperature for the bipolar reset state. While the conventional reset state, obtained under either positive or negative voltage, shows crystallization around 150°C, the bipolar reset show a gradual decline of resistance suggestive of redistribution (e.g., diffusion) of atomic species in the depleted gap. A residual resistance window of 10x is achieved at 250°C, supporting the use of bipolar switching PCM for high temperature application. For instance, bipolar switching PCM might be suitable to sustain retention tests for few minutes at 260°C, which are required for embedded applications [5]. These results might thus open novel application spaces by overcoming the limitations of phase transition in conventional PCM. [1] T. Kato and K. Tanaka, “Electronic properties of amorphous and crystalline Ge2Sb2Te5 films,” Jpn. J. Appl. Phys. 44, 7340 (2005).[2] G. Navarro, et al., “Trade-off Between SET and Data Retention Performance Thanks to Innovative Materials for Phase-Change Memory,” IEDM Tech. Dig. 570 (2013). [3] H. Y. Cheng, et al., “A High Performance Phase Change Memory with Fast Switching Speed and High Temperature Retention by Engineering the GexSbyTez phase Change Material,” IEDM Tech. Dig. 51 (2011). [4] N. Ciocchini, E. Palumbo, M. Borghi, P. Zuliani, R. Annunziata, D. Ielmini, “Modeling resistance instabilities of set and reset states in phase change memory with Ge-rich GeSbTe,” IEEE Trans. Electron Devices 61, 2136 (2014). [5] P. Zuliani, et al., “Overcoming Temperature Limitations in Phase Change Memories With Optimized GexSbyTez,” IEEE Trans. Electron Devices 60, 4020 (2013).

Reversible Phase Transition in Gete through Resonance Bond Swiching

Phase change materials, especially those along the GeTe-Sb2Te3 tie-line (GST), have been widely used in applications of memory devices. Using these materials, information can be stored as optical and electrical change contrast arising from thermally induced structural transitions between the crystalline and amorphous phases. Amorphous phase is obtained by heating the material of crystalline phase upon melting temperature and cooling it fast enough so that it solidify in the amorphous phase. On the other hand, crystalline phase is obtained by heating the material of amorphous phase during relative longer time (a few ns) than amorphization time within appropriate temperature range between crystallization temperature and melting temperature. Contrary to this relatively small difference of heating condition, their physical properties are extremely different from each other. Besides, their fast switching properties and rather good reversibility show promising characteristics for phase change materials as a candidate material for universal memory as well as a most intriguing topic in material society. Despite of these specific material properties, the fundamental reasons for this reversible and fast transition are still in a debate and needs to be understood more considerably as a view point of local structure and orbital environment. Many of the previous studies for understanding phase change mechanism concentrated in comparison of orbital structure between the crystalline phase and amorphous phase. However, the investigation on the modified crystalline phases which is weakly perturbed by thermal variation or external stress could show possible phase transition path. In this study, using uni-axial stress (bending stress), the crystalline GeTe is modulated to have reversible structure deformation which gives rise to drastic change on optical property with resonance bond breaking. Modulated GeTe also shows reversible electrical change caused by orbital rearrangement and irreversible electrical change caused by defect formation. A stress which is relatively smaller thermodynamic perturbation than heat also can be an important variable in phase change mechanism and it might support the reason why both of set and reset state in phase change memory contain various of chemical states.

Enriched dairy fat matrix diet prevents early life lipopolysaccharide-induced spatial memory impairment at adulthood

Polyunsaturated fatty acids (PUFAs) are essential fatty acids, which are critical for brain development and later life cognitive functions. The main brain PUFAs are docosahexaenoic acid (DHA) for the n-3 family and arachidonic acid (ARA) for the n-6 family, which are provided to the post-natal brain by breast milk or infant formula. Recently, the use of dairy lipids (DL) in replacement of vegetable lipids (VL) was revealed to potently promote the accretion of DHA in the developing brain. Brain DHA, in addition to be a key component of brain development, display potent anti-inflammatory activities, which protect the brain from adverse inflammatory events. In this work, we evaluated the protective effect of partial replacement of VL by DL, supplemented or not with DHA and ARA, on post-natal inflammation and its consequence on memory. Mice were fed with diets poor in vegetal n-3 PUFA (Def VL), balanced in vegetal n-3/n-6 PUFA (Bal VL), balanced in dairy lipids (Bal DL) or enriched in DHA and ARA (Supp VL; Supp DL) from the first day of gestation until adulthood. At post-natal day 14 (PND14), pups received a single administration of the endotoxin lipopolysaccharide (LPS) and brain cytokine expression, microglia phenotype and neurogenesis were measured. In a second set of experiments, memory and neurogenesis were measured at adulthood. Overall, our data showed that lipid quality of the diet modulates early life LPS effect on microglia phenotype, brain cytokine expression and neurogenesis at PND14 and memory at adulthood. In particular, Bal DL diet protects from the adverse effect of early life LPS exposure on PND14 neurogenesis and adult spatial memory.

Analogous selection processes in declarative and procedural working memory: N-2 list-repetition and task-repetition costs

Working memory (WM) holds and manipulates representations for ongoing cognition. Oberauer (Psychology of Learning and Motivation, 51, 45-100, 2009) distinguishes between two analogous WM sub-systems: a declarative WM which handles the objects of thought, and a procedural WM which handles the representations of (cognitive) actions. Here, we assessed whether analogous effects are observed when participants switch between memory sets (declarative representations) and when they switch between task sets (procedural representations). One mechanism assumed to facilitate switching in procedural WM is the inhibition of previously used, but currently irrelevant task sets, as indexed by n-2 task-repetition costs (Mayr & Keele, Journal of Experimental Psychology: General, 129(1), 4-26, 2000). In this study we tested for an analogous effect in declarative WM. We assessed the evidence for n-2 list-repetition costs across eight experiments in which participants switched between memory lists to perform speeded classifications, mental arithmetic, or a local recognition test. N-2 list-repetition costs were obtained consistently in conditions assumed to increase interference between memory lists, and when lists formed chunks in long-term memory. Further analyses across experiments revealed a substantial contribution of episodic memory to n-2 list-repetition costs, thereby questioning the interpretation of n-2 repetition costs as reflecting inhibition. We reanalyzed the data of eight task-switching experiments, and observed that episodic memory also contributes to n-2 task-repetition costs. Taken together, these results show analogous processing principles in declarative and procedural WM, and question the relevance of inhibitory processes for efficient switching between mental sets.

Efficient sequential and parallel algorithms for finding edit distance based motifs.

BackgroundMotif search is an important step in extracting meaningful patterns from biological data. The general problem of motif search is intractable and there is a pressing need to develop efficient, exact and approximation algorithms to solve this problem. In this paper, we present several novel, exact, sequential and parallel algorithms for solving the (l,d) Edit-distance-based Motif Search (EMS) problem: given two integers l,d and n biological strings, find all strings of length l that appear in each input string with atmost d errors of types substitution, insertion and deletion.MethodsOne popular technique to solve the problem is to explore for each input string the set of all possible l-mers that belong to the d-neighborhood of any substring of the input string and output those which are common for all input strings. We introduce a novel and provably efficient neighborhood exploration technique. We show that it is enough to consider the candidates in neighborhood which are at a distance exactly d. We compactly represent these candidate motifs using wildcard characters and efficiently explore them with very few repetitions. Our sequential algorithm uses a trie based data structure to efficiently store and sort the candidate motifs. Our parallel algorithm in a multi-core shared memory setting uses arrays for storing and a novel modification of radix-sort for sorting the candidate motifs.ResultsThe algorithms for EMS are customarily evaluated on several challenging instances such as (8,1), (12,2), (16,3), (20,4), and so on. The best previously known algorithm, EMS1, is sequential and in estimated 3 days solves up to instance (16,3). Our sequential algorithms are more than 20 times faster on (16,3). On other hard instances such as (9,2), (11,3), (13,4), our algorithms are much faster. Our parallel algorithm has more than 600 % scaling performance while using 16 threads.ConclusionsOur algorithms have pushed up the state-of-the-art of EMS solvers and we believe that the techniques introduced in this paper are also applicable to other motif search problems such as Planted Motif Search (PMS) and Simple Motif Search (SMS).Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2789-9) contains supplementary material, which is available to authorized users.

The special role of item-context associations in the direct-access region of working memory.

The three-embedded-component model of working memory (WM) distinguishes three representational states corresponding to three WM regions: activated long-term memory, direct-access region (DAR), and focus of attention. Recent neuroimaging research has revealed that access to the DAR is associated with enhanced hippocampal activity. Because the hippocampus mediates the encoding and retrieval of item-context associations, it has been suggested that this hippocampal activation is a consequence of the fact that item-context associations are particularly strong and accessible in the DAR. This study provides behavioral evidence for this view using an item-recognition task to assess the effect of non-intentional encoding and maintenance of item-location associations across WM regions. Five pictures of human faces were sequentially presented in different screen locations followed by a recognition probe. Visual cues immediately preceding the probe indicated the location thereof. When probe stimuli appeared in the same location that they had been presented within the memory set, the presentation of the cue was expected to elicit the activation of the corresponding WM representation through the just-established item-location association, resulting in faster recognition. Results showed this same-location effect, but only for items that, according to their serial position within the memory set, were held in the DAR.