Coherent Memory Research Articles

Formal Specification of Memory Coherence Protocol

Memory coherence is the most fundamental re-quirement in a shared virtual memory system where there are concurrent as well as loosely coupled processes. These processes can demand a page for reading or writing. The memory is called coherent if the last update in a page remains constant for each process until the owner of that page does not change it. The ownership is transferred to a process interested to update that page. In [Kai LI, and Paul Hudak. Memory Coherence in Shared Virtual Memory Systems, 1986. Proc. of Fifth Annual ACM Symposium on Principles of Distributed Computing.], algorithms ensuring memory coherence are given. We formally specify these protocols and report the improvements through formal analysis. The protocols are specified in UPPAAL, i.e., a tool for modeling, validation and verification of real-time systems.

Transient Dynamics of Stimulated Raman Scattering in Gas‐Filled Hollow‐Core Photonic Crystal Fibers

A theoretical and numerical investigation of transient dynamics of stimulated Raman scattering (SRS) inside gas‐filled hollow‐core photonic crystal fibers (HCPCFs) is reported here. A clear link between the transient dynamics and the coherent memory of the SRS interaction is demonstrated. In addition, the role of pulse width, pump power, fiber length, and gaseous medium in the transient dynamics of SRS in HCPCFs is discussed. It is shown that the coherent memory can serve as a convenient parameter to control the SRS propagation regime.

Revisiting Scalable Coherent Shared Memory

Scalable and coherent shared memory has been a long-sought-after but elusive goal. In contrast to today’s popular distributed-computing models, the authors present a software-defined server architecture that is a scale-up shared-memory multiprocessor, yet uses ubiquitous commodity scale-out clusters.

Remembering Reconstruction: Struggles Over the Meaning of America's Most Turbulent Era ed. by Carole Emberton and Bruce E. Baker

Reviewed by: Remembering Reconstruction: Struggles Over the Meaning of America's Most Turbulent Era ed. by Carole Emberton and Bruce E. Baker April E. Holm Remembering Reconstruction: Struggles Over the Meaning of America's Most Turbulent Era. Edited by Carole Emberton and Bruce E. Baker. Introduction by W. Fitzhugh Brundage. (Baton Rouge: Louisiana State University Press, 2017. Pp. viii, 286. $45.00, ISBN 978-0-8071-6602-4.) We are now well into the sesquicentennial of Reconstruction, although it is passing with much less fanfare than did the anniversaries of the Civil War. There is not much public representation of Reconstruction and little contemporary consensus on lessons to be drawn from the period. This has not always been the case. From the late nineteenth century to the mid-twentieth century, white Americans shared a strong, coherent historical memory of Reconstruction. It held that former slaves had been granted suffrage too quickly, that northern zealots had lined their own pockets while trampling on the rights of white southerners, and that white southerners were themselves helpless victims of corrupt state governments during the darkest era of American history. This narrative did not go uncontested, however. Remembering Reconstruction: Struggles Over the Meaning of America's Most Turbulent Era, a collection of essays edited by Carole Emberton and Bruce E. Baker, offers a timely series of meditations on the varied and surprising ways memories of Reconstruction have been employed in the 140 years since it ended. This reassessment is particularly fitting because, as W. Fitzhugh Brundage points out in his incisive introduction, professional historians were deeply involved in producing a racist narrative of Reconstruction that justified the disenfranchisement and segregation of African American southerners. This collection of ten essays is divided into four sections: one on white supremacist memories of Reconstruction, one on black memories of Reconstruction, one on Reconstruction and American imperialism, and one on memories of Reconstruction after the civil rights era. The essays span more than one hundred years of American history, from the Jim Crow era to the present. Taken as a whole, they remind us that Americans have remembered—and forgotten—Reconstruction in complex and challenging ways. They make a case for the lasting importance of those memories even as popular consensus around the meaning of the period has eroded. While there is some unevenness in this collection in terms of polish and depth of historiographical intervention, the essays cohere around several key themes. As K. Stephen Prince and Jason Morgan Ward emphasize, the political and social memories of Reconstruction were vital to implementing and upholding white supremacy. However, as Shawn Leigh Alexander and Justin Behrend argue, African Americans consistently promoted counternarratives that resisted dominant white [End Page 1017] interpretations of the era. Several essays in the collection, such as those by Mark Elliott and Natalie J. Ring, demonstrate how turn-of-the-twentieth-century Americans applied the lessons they drew from Reconstruction to varied enterprises, such as imperial projects and domestic reform. Some essays in particular expand our understanding of how the memory of Reconstruction has been used. In "The Freedwoman's Tale: Reconstruction Remembered in the Federal Writers' Project Ex-Slave Narratives," Carole Emberton challenges assumptions about the moment of emancipation and what followed. She begins with a 1930s narrative in which a former slave proudly describes how her erstwhile master, a Ku Klux Klan member, helped suppress an uprising among freedpeople at a neighboring plantation. Although this incident was seemingly at odds with what we would expect of former slaves at the moment of emancipation, Emberton persuasively argues that this narrative (and other sources like it) should not be dismissed. They provide much-needed insight into the lived experience of emancipation. Rather than constituting an uncomplicated "Jubilee moment," emancipation ushered in a period of violence that taught enslaved people the importance of maintaining strong relationships with local whites and the dangers of aligning too closely with any political party (p. 111). In connecting southern agrarian violence of the 1930s to ex-slave narratives about the Reconstruction era, Emberton concludes that the lessons learned after emancipation applied well into the twentieth century. In "'A Bitter Memory Upon Which Terms of Peace Would Rest': Woodrow Wilson, the Reconstruction...

Prefrontal θ-Burst Stimulation Disrupts the Organizing Influence of Active Short-Term Retrieval on Episodic Memory.

Dorsolateral prefrontal cortex (DLPFC) is thought to organize items in working memory and this organizational role may also influence long-term memory. To causally test this hypothesized role of DLPFC in long-term memory formation, we used θ-burst noninvasive stimulation (TBS) to modulate DLPFC involvement in a memory task that assessed the influence of active short-term retrieval on later memory. Human subjects viewed three objects on a grid and then either actively retrieved or passively restudied one object’s location after a brief delay. Long-term memory for the other objects was assessed after a delay to evaluate the beneficial role of active short-term retrieval on subsequent memory for the entire set of object locations. We found that DLPFC TBS had no significant effects on short-term memory. In contrast, DLPFC TBS impaired long-term memory selectively in the active-retrieval condition but not in the passive-restudy condition. These findings are consistent with the hypothesized contribution of DLPFC to the organizational processes operative during active short-term retrieval that influence long-term memory, although other regions that were not stimulated could provide similar contributions. Notably, active-retrieval and passive-restudy conditions were intermixed, and therefore nonspecific influences of stimulation were well controlled. These results suggest that DLPFC is causally involved in organizing event information during active retrieval to support coherent long-term memory formation.

The Importance of Memory Specificity and Memory Coherence for the Self: Linking Two Characteristics of Autobiographical Memory.

Autobiographical memory forms a network of memories about personal experiences that defines and supports well-being and effective functioning of the self in various ways. During the last three decades, there have been two characteristics of autobiographical memory that have received special interest regarding their role in psychological well-being and psychopathology, namely memory specificity and memory coherence. Memory specificity refers to the extent to which retrieved autobiographical memories are specific (i.e., memories about a particular experience that happened on a particular day). Difficulty retrieving specific memories interferes with effective functioning of the self and is related to depression and post-traumatic stress disorder. Memory coherence refers to the narrative expression of the overall structure of autobiographical memories. It has likewise been related to psychological well-being and the occurrence of psychopathology. Research on memory specificity and memory coherence has developed as two largely independent research domains, even though they show much overlap. This raises some important theoretical questions. How do these two characteristics of autobiographical memory relate to each other, both theoretically and empirically? Additionally, how can the integration of these two facilitate our understanding of the importance of autobiographical memory for the self? In this article, we give a critical overview of memory specificity and memory coherence and their relation to the self. We link both features of autobiographical memory by describing some important similarities and by formulating hypotheses about how they might relate to each other. By situating both memory specificity and memory coherence within Conway and Pleydell-Pearce’s Self-Memory System, we make a first attempt at a theoretical integration. Finally, we suggest some new and exciting research possibilities and explain how both research fields could benefit from integration in future research.

Neural Mechanisms Underlying the Processing of Temporal Information in Episodic Memory and Its Disturbance

Episodic memory is defined as memory for personally experienced events, and includes memory content and contextual information of time and space. Previous neuroimaging and neuropsychological studies have demonstrated three possible roles of the temporal context in episodic memory. First, temporal information contributes to the arrangement of temporal order for sequential events in episodic memory, and this process is involved in the lateral prefrontal cortex. The second possible role of temporal information in episodic memory is the segregation between memories of multiple events, which are segregated by cues of different time information. The role of segregation is associated with the orbitofrontal regions including the orbitofrontal cortex and basal forebrain region. Third, temporal information in episodic memory plays an important role in the integration of multiple components into a coherent episodic memory, in which episodic components in the different modalities are combined by temporal information as an index. The role of integration is mediated by the medial temporal lobe including the hippocampus and parahippocampal gyrus. Thus, temporal information in episodic memory could be represented in multiple stages, which are involved in a network of the lateral prefrontal, orbitofrontal, and medial temporal lobe regions.

Non-Gaussian statistics of extreme events in stimulated Raman scattering: The role of coherent memory and source noise

Non-Gaussian statistics of extreme events in stimulated Raman scattering: The role of coherent memory and source noise

A chip-integrated coherent photonic-phononic memory

Controlling and manipulating quanta of coherent acoustic vibrations—phonons—in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk.

Supplemental Material for Negative Emotional Content Disrupts the Coherence of Episodic Memories

Supplemental Material for Negative Emotional Content Disrupts the Coherence of Episodic Memories

An Architecture for Integrated Near-Data Processors

To increase the performance of data-intensive applications, we present an extension to a CPU architecture that enables arbitrary near-data processing capabilities close to the main memory. This is realized by introducing a component attached to the CPU system-bus and a component at the memory side. Together they support hardware-managed coherence and virtual memory support to integrate the near-data processors in a shared-memory environment. We present an implementation of the components, as well as a system-simulator, providing detailed performance estimations. With a variety of synthetic workloads we demonstrate the performance of the memory accesses, the mixed fine- and coarse-grained coherence mechanisms, and the near-data processor communication mechanism. Furthermore, we quantify the inevitable start-up penalty regarding coherence and data writeback, and argue that near-data processing workloads should access data several times to offset this penalty. A case study based on the Graph500 benchmark confirms the small overhead for the proposed coherence mechanisms and shows the ability to outperform a real CPU by a factor of two.

Evaluating WAIS–IV structure through a different psychometric lens: structural causal model discovery as an alternative to confirmatory factor analysis

Objective: Since the publication of the WAIS–IV in the U.S. in 2008, efforts have been made to explore the structural validity by applying factor analysis to various samples. This study aims to achieve a more fine-grained understanding of the structure of the Dutch language version of the WAIS–IV (WAIS–IV–NL) by applying an alternative analysis based on causal modeling in addition to confirmatory factor analysis (CFA). The Bayesian Constraint-based Causal Discovery (BCCD) algorithm learns underlying network structures directly from data and assesses more complex structures than is possible with factor analysis. Method: WAIS–IV–NL profiles of two clinical samples of 202 patients (i.e. patients with temporal lobe epilepsy and a mixed psychiatric outpatient group) were analyzed and contrasted with a matched control group (N = 202) selected from the Dutch standardization sample of the WAIS–IV–NL to investigate internal structure by means of CFA and BCCD. Results: With CFA, the four-factor structure as proposed by Wechsler demonstrates acceptable fit in all three subsamples. However, BCCD revealed three consistent clusters (verbal comprehension, visual processing, and processing speed) in all three subsamples. The combination of Arithmetic and Digit Span as a coherent working memory factor could not be verified, and Matrix Reasoning appeared to be isolated. Conclusions: With BCCD, some discrepancies from the proposed four-factor structure are exemplified. Furthermore, these results fit CHC theory of intelligence more clearly. Consistent clustering patterns indicate these results are robust. The structural causal discovery approach may be helpful in better interpreting existing tests, the development of new tests, and aid in diagnostic instruments.

Out of place, out of mind: Schema-driven false memory effects for object-location bindings.

Events consist of diverse elements, each processed in specialized neocortical networks, with temporal lobe memory systems binding these elements to form coherent event memories. We provide a novel theoretical analysis of an unexplored consequence of the independence of memory systems for elements and their bindings, 1 that raises the paradoxical prediction that schema-driven false memories can act solely on the binding of event elements despite the superior retrieval of individual elements. This is because if 2, or more, schema-relevant elements are bound together in unexpected conjunctions, the unexpected conjunction will increase attention during encoding to both the elements and their bindings, but only the bindings will receive competition with evoked schema-expected bindings. We test our model by examining memory for object-location bindings in recognition (Study 1) and recall (Studies 2 and 3) tasks. After studying schema-relevant objects in unexpected locations (e.g., pan on a stool in a kitchen scene), participants who then viewed these objects in expected locations (e.g., pan on stove) at test were more likely to falsely remember this object-location pairing as correct, compared with participants that viewed a different unexpected object-location pairing (e.g., pan on floor). In recall, participants were more likely to correctly remember individual schema-relevant objects originally viewed in unexpected, as opposed to expected locations, but were then more likely to misplace these items in the original room scene to expected places, relative to control schema-irrelevant objects. Our theoretical analysis and novel paradigm provide a tool for investigating memory distortions acting on binding processes. (PsycINFO Database Record

Reduced multimodal integration of memory features following continuous theta burst stimulation of angular gyrus

BackgroundLesions of the angular gyrus (AnG) region of human parietal cortex do not cause amnesia, but appear to be associated with reduction in the ability to consciously experience the reliving of previous events. Objectives/HypothesisWe used continuous theta burst stimulation to test the hypothesis that the cognitive mechanism implicated in this memory deficit might be the integration of retrieved sensory event features into a coherent multimodal memory representation. MethodsHealthy volunteers received stimulation to AnG or a vertex control site after studying stimuli that each comprised a visual object embedded in a scene, with the name of the object presented auditorily. Participants were then asked to make memory judgments about the studied stimuli that involved recollection of single event features (visual or auditory), or required integration of event features within the same modality, or across modalities. ResultsParticipants' ability to retrieve context features from across multiple modalities was significantly reduced after AnG stimulation compared to stimulation of the vertex. This effect was observed only for the integration of cross-modal context features but not for integration of features within the same modality, and could not be accounted for by task difficulty as performance was matched across integration conditions following vertex stimulation. ConclusionThese results support the hypothesis that AnG is necessary for the multimodal integration of distributed cortical episodic features into a unified conscious representation that enables the experience of remembering.

Episodic versus semantic memory impairments and deficits in discourse production

Event Abstract Back to Event Episodic versus semantic memory impairments and deficits in discourse production Bruna Seixas Lima1, 2*, Kelly Murphy3, 4, Angela Troyer3, 4, Brian Levine3, 5, Naida Graham1, 2, Carol Leonard1, 6, David Tang-Wai7, Sandra E. Black8, 9, 10, 11 and Elizabeth Rochon1, 2 1 University of Toronto, Rehabilitation Sciences Institute, Canada 2 Toronto Rehabilitaion Institute, Canada 3 University of Toronto, Department of Psychology, Canada 4 Baycrest Health Sciences, Neuropsychology and Cognitive Health, Canada 5 Baycrest Centre, Rotman Research Institute, Canada 6 University of Ottawa, Audiology and Speech-Language Pathology Program, Canada 7 University Health Network Memory Clinic, Department of Medicine, Canada 8 Sunnybrook Health Sciences, Canada 9 University of Toronto, Institute of Medical Science, Canada 10 Sunnybrook Health Sciences, L.C. Campbell Cognitive Neurology Research Unit, Canada 11 Heart and Stroke Foundation, Partnership for Stroke Recovery, Canada Discourse production requires organization, integration and coordination of linguistic units. These processes involve cognitive skills other than language, such as memory (Glosser & Deser, 1990). Neurodegenerative syndromes commonly affect autobiographical memory recall and often are accompanied by linguistic disruption. Semantic variant primary progressive aphasia (svPPA) is a disorder which affects the semantic memory system and whose most prominent symptom is aphasia (Gorno-Tempini et al., 2011). In mild cognitive impairment (MCI) there is greater than expected cognitive decline in comparison to healthy-aging, with high rates of progression to Alzheimer’s disease (AD) (Artero et al., 2006). Language impairment observed in MCI and AD patients includes impairments in verbal fluency, naming and discourse production (Murphy et al., 2006; Henry et al., 2004; Harris et al., 2008). Semantic memory (general knowledge) is known to be affected in svPPA but appears intact in amnestic MCI (aMCI). By contrast, episodic memory (memories of specific events) is impaired in aMCI, but spared in svPPA (Murphy et al., 2008, Moss et al., 2003). These two types of memory are necessary for autobiographical memory recall. This study aims to investigate discourse coherence and autobiographical memory recall in svPPA and aMCI patients. Given the impairments observed in these populations and the intrinsic relationship between language and memory, we predicted the discourse production of these groups would be differentially affected when recalling information related to the type of memory affected in each syndrome. To date, we have analysed the speech of 18 svPPA patients and 18 healthy controls matched for age and education, and the speech of five aMCI patients and five matched controls. Discourse was elicited by asking participants to recall autobiographical events. Memory recall was evaluated using the Autobiographical Interview (Levine et al., 2002). Narratives were transcribed and segmented into utterances which were classified as semantic or episodic details. In addition, a coherence rating scale was used to analyse the relevance and informativeness of these details to the topic of discourse. Details received a score from 0 to 3. The weighted average score was calculated for the whole narrative and for the semantic and episodic composites separately. Independent samples (corrected for multiple comparisons) t-tests showed that aMCI patients produced shorter narratives than controls (p<.001), while the linguistic output of svPPA patients was comparable to that of the controls. Both svPPA (p<.001) and aMCI groups (p<.001) produced fewer episodic details than controls, while producing a comparable number of semantic details. Interestingly, svPPA patients presented with deficits in overall coherence (p<.001), which were not observed in aMCI patients. Additionally, the deficit in coherence of the svPPA patients was observed when producing semantic (p<.001) but not episodic details. These preliminary results suggest that impairment in the semantic memory system may be linked to reduced discourse coherence. Ongoing analyses will incorporate more aMCI participants. We expect this study will aid in the understanding of the relationship between memory and linguistic processes and may support the development of new diagnostic tools for cognitively impaired individuals. Acknowledgements This work was supported by the Canadian Institutes of Health Research (grant numbers 82744 and 130462).

Study the Influential Factors in the Hit Rate of Cache Memory for a Multiprocessors System

This paper presents an analytical and deductive study at software and hardware level for a symmetric multiprocessors system. Basic influential factors in the performance as cache memory size, processors number, and coherence protocols of cache memories are defined and compared, and a different simulations and evaluations of multiple experimental values of these parameters have been carried out also. In order to speed up the parallel processing and to improve the performance for realizing the execution in real time, harmonious values of these factors are obtained as experimental results.

Visual Sampling Predicts Hippocampal Activity.

The hippocampal and oculomotor networks have each been studied extensively for their roles in the binding of information and gaze function, respectively. Despite the evidence that individuals with amnesia whose damage includes the hippocampus show alterations in their eye movement patterns and recent findings that the two systems are anatomically connected, it has not been demonstrated whether visual exploration is related to hippocampal activity in neurologically intact adults. In this combined fMRI-eye-tracking study, we show how hippocampal responses scale with the number of gaze fixations made during viewing of novel, but not repeated, faces. These findings provide new evidence suggesting that the hippocampus plays an important role in the binding of information, as sampled by gaze fixations, during visual exploration.

Distinct roles of hippocampus and medial prefrontal cortex in spatial and nonspatial memory.

In earlier work, patients with hippocampal damage successfully path integrated, apparently by maintaining spatial information in working memory. In contrast, rats with hippocampal damage were unable to path integrate, even when the paths were simple and working memory might have been expected to support performance. We considered possible ways to understand these findings. We tested rats with either hippocampal lesions or lesions of medial prefrontal cortex (mPFC) on three tasks of spatial or nonspatial memory: path integration, spatial alternation, and a nonspatial alternation task. Rats with mPFC lesions were impaired on both spatial and nonspatial alternation but performed normally on path integration. By contrast, rats with hippocampal lesions were impaired on path integration and spatial alternation but performed normally on nonspatial alternation. We propose that rodent neocortex is limited in its ability to construct a coherent spatial working memory of complex environments. Accordingly, in tasks such as path integration and spatial alternation, working memory cannot depend on neocortex alone. Rats may accomplish many spatial memory tasks by relying on long-term memory. Alternatively, they may accomplish these tasks within working memory through sustained coordination between hippocampus and other cortical brain regions such as mPFC, in the case of spatial alternation, or parietal cortex in the case of path integration. © 2016 Wiley Periodicals, Inc.

High-Fidelity Universal Gate Set for ^{9}Be^{+} Ion Qubits.

We report high-fidelity laser-beam-induced quantum logic gates on magnetic-field-insensitive qubits comprised of hyperfine states in ^{9}Be^{+} ions with a memory coherence time of more than 1s. We demonstrate single-qubit gates with an error per gate of 3.8(1)×10^{-5}. By creating a Bell state with a deterministic two-qubit gate, we deduce a gate error of 8(4)×10^{-4}. We characterize the errors in our implementation and discuss methods to further reduce imperfections towards values that are compatible with fault-tolerant processing at realistic overhead.

Development and Validation of the Awareness of Narrative Identity Questionnaire (ANIQ).

The utility of a narrative approach to identity and its role in psychological functioning are becoming increasingly recognized across various fields of inquiry. The current study aimed to develop a quantitative, self-report measure of the awareness of narrative identity and how globally coherent one's autobiographical memories are perceived to be, specifically, in terms of temporal ordering, causal associations, and the perception of unifying themes. The construct validity and reliability of the Awareness of Narrative Identity Questionnaire (ANIQ) were assessed across three studies. In the first study, exploratory factor analysis of the responses of a large sample ( N = 441, M [age in years] = 33.1, SD = 15.2) to an initial item pool resulted in a 20-item four-factor structure congruent with the proposed subscales, and convergent and divergent validity were established. In the second study, and with a different sample ( N = 320, M [age in years] = 26.2, SD = 4.0), further evidence for the factor structure was provided through confirmatory factor analysis. Validity findings from Study 1 were replicated and extended on, and test-retest reliabilities were found to be high ( r = .72-.79). Importantly, in the third study ( N = 71, M [age in years] = 24.9, SD = 6.9), criterion validity was established, whereby the ANIQ subscales were demonstrated to be associated with dimensions of narrative coherence coded from written turning-point narratives. Across all studies, the internal reliabilities for the subscales were high (α = .86-.96). The ANIQ represents a valid, psychometrically sound, and novel method of assessing the awareness of narrative identity and autobiographical memory coherence.