Memory Profile Research Articles

Performance and Symptom Validity in Outpatient Pediatric Neuropsychological Evaluations

ABSTRACT This study aimed to clarify the value of using different types of validity measures in pediatric neuropsychological evaluations. We examined the relationship between performance (PVT) and symptom (SVT) validity tests as well as demographic variables and results from a screening test of learning and memory (i.e. Child and Adolescent Memory Profile [ChAMP]) in a mixed pediatric sample (n = 103). There was minimal overlap between PVT and SVT failures. Regression analyses demonstrated that PVT results, parental education, and history of special education were statistically significant predictors of ChAMP results, whereas SVT results were not.

Pyrimidine de novo synthesis inhibition selectively blocks effector but not memory T cell development.

Blocking pyrimidine de novo synthesis by inhibiting dihydroorotate dehydrogenase is used to treat autoimmunity and prevent expansion of rapidly dividing cell populations including activated T cells. Here we show memory T cell precursors are resistant to pyrimidine starvation. Although the treatment effectively blocked effector T cells, the number, function and transcriptional profile of memory T cells and their precursors were unaffected. This effect occurred in a narrow time window in the early T cell expansion phase when developing effector, but not memory precursor, T cells are vulnerable to pyrimidine starvation. This vulnerability stems from a higher proliferative rate of early effector T cells as well as lower pyrimidine synthesis capacity when compared with memory precursors. This differential sensitivity is a drug-targetable checkpoint that efficiently diminishes effector T cells without affecting the memory compartment. This cell fate checkpoint might therefore lead to new methods to safely manipulate effector T cell responses.

Using serial position effects to investigate memory dysfunction in homeless and precariously housed persons

Background: Homeless and precariously housed persons exhibit significant memory impairment, but the component processes underlying memory dysfunction have not been explored. We examined the serial position profile (i.e., primacy and recency effects) of verbal memory and its neuroanatomical correlates to identify the nature of memory difficulties in a large cohort of homeless and precariously housed adults. Method: The sample included 227 community-dwelling homeless and precariously housed adults. Serial position scores (primacy, middle, recency) were computed using the Hopkins Verbal Learning Test-Revised. Paired sample t-tests were used to compare percent recall from each word list region. Age-adjusted correlations assessed associations between serial position scores and other cognitive domains (attention, processing speed, executive functioning). Regression analyses were conducted to examine regional brain volumes of interest (hippocampus, entorhinal cortex, dorsolateral prefrontal cortex [DLPFC]) and their differential associations with serial position scores. Results: The serial position profile was characterized by a diminished recency effect in relation to the primacy effect. Serial position scores positively correlated with sustained attention and cognitive control. Larger hippocampal volume was associated with better primacy item recall. DLPFC volume was not associated with serial position recall after adjustment for false discovery rate. There were no associations between regional brain volumes and recency item recall. Conclusion: Our results suggest that commonly reported memory difficulties in homeless and precariously housed adults are likely secondary to a core deficit in executive control due to compromised frontal lobe functioning. These findings have implications for cognitive rehabilitation in this complex and vulnerable group.

Superior verbal learning and memory in pediatric brain tumor survivors treated with proton versus photon radiotherapy.

Radiotherapy for pediatric brain tumor has been associated with late cognitive effects. Compared to conventional photon radiotherapy (XRT), proton radiotherapy (PRT) delivers lower doses of radiation to healthy brain tissue. PRT has been associated with improved long-term cognitive outcomes compared to XRT. However, there is limited research comparing the effects of XRT and PRT on verbal memory. Survivors of pediatric brain tumor treated with either XRT (n = 29) or PRT (n = 51) completed neuropsychological testing > 1 year following radiotherapy. Performance on neuropsychological measures was compared between treatment groups using analysis of covariance. Chi-squared tests of independence were used to compare the frequency of encoding, retrieval, and intact memory profiles between treatment groups. Associations between memory performance and other neurobehavioral measures were examined using Pearson correlation. Overall, patients receiving PRT demonstrated superior verbal learning and recall compared to those treated with XRT. Encoding and retrieval deficits were more common in the XRT group than the PRT group, with encoding problems being most prevalent. The PRT group was more likely to engage in semantic clustering strategies, which predicted better encoding and retrieval. Encoding ability was associated with higher intellectual and adaptive functioning, and fewer parent-reported concerns about day-to-day attention and cognitive regulation. Results suggest that PRT is associated with verbal memory sparing, driven by effective encoding and use of learning strategies. Future work may help to clarify underlying neural mechanisms associated with verbal memory decline, which will better inform treatment approaches. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Chronic lymphocytic leukemia presence impairs antigen-specific CD8+ T-cell responses through epigenetic reprogramming towards short-lived effectors.

T-cell dysregulation in chronic lymphocytic leukemia (CLL) associates with low response rates to autologous T cell-based therapies. How CLL affects antigen-specific T-cell responses remains largely unknown. We investigated (epi)genetic and functional consequences of antigen-specific T-cell responses in presence of CLL in vitro and in an adoptive-transfer murine model. Already at steady-state, antigen-experienced patient-derived T cells were skewed towards short-lived effector cells (SLEC) at the expense of memory-precursor effector cells (MPEC). Stimulation of these T cells in vitro showed rapid induction of effector genes and suppression of key memory transcription factors only in presence of CLL cells, indicating epigenetic regulation. This was investigated in vivo by following antigen-specific responses of naïve OT-I CD8+ cells to mCMV-OVA in presence/absence of TCL1 B-cell leukemia. Presence of leukemia resulted in increased SLEC formation, with disturbed inflammatory cytokine production. Chromatin and transcriptome profiling revealed strong epigenetic modifications, leading to activation of an effector and silencing of a memory profile through presence of CLL cells. Secondary challenge in vivo confirmed dysfunctional memory responses by antigen-experienced OT-I cells generated in presence of CLL. Altogether, we show that presence of CLL induces a short-lived effector phenotype and impaired memory responses by epigenetic reprogramming during primary responses.

New Child and Adolescent Memory Profile Embedded Performance Validity Test.

It is essential to interpret performance validity tests (PVTs) that are well-established and have strong psychometrics. This study evaluated the Child and Adolescent Memory Profile (ChAMP) Validity Indicator (VI) using a pediatric sample with traumatic brain injury (TBI). A cross-sectional sample of N = 110 youth (mean age = 15.1years, standard deviation [SD] = 2.4 range = 8-18) on average 32.7weeks (SD = 40.9) post TBI (71.8% mild/concussion; 3.6% complicated mild; 24.6% moderate-to-severe) were administered the ChAMP and two stand-alone PVTs. Criterion for valid performance was scores above cutoffs on both PVTs; criterion for invalid performance was scores below cutoffs on both PVTs. Classification statistics were used to evaluate the existing ChAMP VI and establish a new VI cutoff score if needed. There were no significant differences in demographics or time since injury between those deemed valid (n = 96) or invalid (n = 14), but all ChAMP scores were significantly lower in those deemed invalid. The original ChAMP VI cutoff score was highly specific (no false positives) but also highly insensitive (sensitivity [SN] = .07, specificity [SP] = 1.0). Based on area under the curve (AUC) analysis (0.94), a new cutoff score was established using the sum of scaled scores (VI-SS). A ChAMP VI-SS score of 32 or lower achieved strong SN (86%) and SP (92%). Using a 15% base rate, positive predictive value was 64% and negative predictive value was 97%. The originally proposed ChAMP VI has insufficient SN in pediatric TBI. However, this study yields a promising new ChAMP VI-SS, with classification metrics that exceed any other current embedded PVT in pediatrics.

A preliminary study of the different memory systems in neurofibromatosis type 1: What is impaired and what is spared?

BackgroundSince 1990's, the cognitive profile of children with a neurofibromatosis type 1 (NF1) has been refined by many different studies. Children with NF1 may exhibit a variety of cognitive dysfunctions. Memory difficulties have been reported, but the results are contradictory and, compared to other cognitive functions, memory has been less evaluated. ObjectiveThe aim of this study was to investigate the memory profile in NF1 with a particular population, children with NF1 without attention deficit hyperactivity disorder (ADHD). MethodsEighteen children with NF1 without ADHD and eighteen typically developing aged from 8 to 12.6 years were compared in terms of both their verbal and visual working memory, anterograde memory, and procedural perceptual-motor memory. We also assessed semantic and autobiographical memory. ResultsOur results indicate the existence of memory difficulties in children with NF1 without ADHD in verbal working and anterograde memory but not in terms of the visual domain. They also experienced difficulties recalling personal memories but these were improved by cueing. However, semantic memory and procedural perceptual-motor memory was preserved. ConclusionsThese results highlight a difference between memory systems in children with NF1 without ADHD and the importance to assess the different memory systems, the nature of information and the processes in long-term memory in NF1 population. However, our results raise questions about the possible links between these difficulties and the executive functions. The specifics of memory profile in children with NF1 must be taken into consideration in these children’s clinical follow-up, in order to understand their learning difficulties and to make adaptations to their care.

Prediction of declarative memory profile in panic disorder patients: a machine learning-based approach.

To develop a classification framework based on random forest (RF) modeling to outline the declarative memory profile of patients with panic disorder (PD) compared to a healthy control sample. We developed RF models to classify the declarative memory profile of PD patients in comparison to a healthy control sample using the Rey Auditory Verbal Learning Test (RAVLT). For this study, a total of 299 patients with PD living in the city of Rio de Janeiro (70.9% females, age 39.9 ± 7.3 years old) were recruited through clinician referrals or self/family referrals. Our RF models successfully predicted declarative memory profiles in patients with PD based on RAVLT scores (lowest area under the curve [AUC] of 0.979, for classification; highest root mean squared percentage [RMSPE] of 17.2%, for regression) using relatively bias-free clinical data, such as sex, age, and body mass index (BMI). Our findings also suggested that BMI, used as a proxy for diet and exercises habits, plays an important role in declarative memory. Our framework can be extended and used as a prospective tool to classify and examine associations between clinical features and declarative memory in PD patients.

Longitudinal characterisation of B and T-cell immune responses after the booster dose of COVID-19 mRNA-vaccine in people with multiple sclerosis using different disease-modifying therapies

BackgroundThe decline of humoral response to COVID-19 vaccine led to authorise a booster dose. Here, we characterised the kinetics of B-cell and T-cell immune responses in patients with multiple sclerosis...

Working memory assessment using cambridge neuropsychological test automated battery can help in the diagnosis of mild cognitive impairment: a systematic review and meta-analysis.

In this study, we investigated working memory (WM) profiles of MCI patients using the Cambridge Neuropsychological Test Automated Battery (CANTAB). We also examined the diagnostic accuracy and possible associated factors as secondary outcomes of the study. We conducted an electronic search on EMBASE, PubMed, and ScienceDirect databases. Studies with MCI participants and using CANTAB battery subtests for the assessment of WM were included. Meta-analysis was conducted using the CMA2 software. Out of 1537 records, 14 studies were covered in this systematic review, and 7 of them were included in the meta-analysis. There was a significant difference between MCI patients and healthy controls in spatial working memory (SWM) (SDM: 0.535; 95%CI 11-96; p-value=0.014), spatial span (SSP) (SDM: 0.649 95%CI 0.297-0.100; p-value<0.01), and rapid visual information processing (RVP) (SDM: 0.52; 95%CI 0.386-0.654; p-value<0.01). WM function of MCI patients was associated with the cerebrospinal fluid (CSF) levels of tau-protein and amyloid-beta (Aβ). WM is an impaired cognitive domain in MCI. CANTAB WM subtests including SSP, SWM, and RVP are accurate enough to be used as a proper assessment tool for the diagnosis of MCI in clinical settings. Tau-protein and Aβ are associated with lower WM scores in MCI patients; however, sex, age, psychiatric disorders, apolipoprotein 4 allele, and functional activity scores cannot affect WM.

E-prop on SpiNNaker 2: Exploring online learning in spiking RNNs on neuromorphic hardware.

In recent years, the application of deep learning models at the edge has gained attention. Typically, artificial neural networks (ANNs) are trained on graphics processing units (GPUs) and optimized for efficient execution on edge devices. Training ANNs directly at the edge is the next step with many applications such as the adaptation of models to specific situations like changes in environmental settings or optimization for individuals, e.g., optimization for speakers for speech processing. Also, local training can preserve privacy. Over the last few years, many algorithms have been developed to reduce memory footprint and computation. A specific challenge to train recurrent neural networks (RNNs) for processing sequential data is the need for the Back Propagation Through Time (BPTT) algorithm to store the network state of all time steps. This limitation is resolved by the biologically-inspired E-prop approach for training Spiking Recurrent Neural Networks (SRNNs). We implement the E-prop algorithm on a prototype of the SpiNNaker 2 neuromorphic system. A parallelization strategy is developed to split and train networks on the ARM cores of SpiNNaker 2 to make efficient use of both memory and compute resources. We trained an SRNN from scratch on SpiNNaker 2 in real-time on the Google Speech Command dataset for keyword spotting. We achieved an accuracy of 91.12% while requiring only 680 KB of memory for training the network with 25 K weights. Compared to other spiking neural networks with equal or better accuracy, our work is significantly more memory-efficient. In addition, we performed a memory and time profiling of the E-prop algorithm. This is used on the one hand to discuss whether E-prop or BPTT is better suited for training a model at the edge and on the other hand to explore architecture modifications to SpiNNaker 2 to speed up online learning. Finally, energy estimations predict that the SRNN can be trained on SpiNNaker2 with 12 times less energy than using a NVIDIA V100 GPU.

Continuity versus change in latent profiles of emotion regulation and working memory during adolescence

Significant structural and functional brain development occurs during early adolescence. These changes underlie developments in central neurocognitive processes such as working memory (WM) and emotion regulation (ER). The preponderance of studies modeling trajectories of adolescent brain development use variable-centered approaches, omitting attention to individual differences that may undergird neurobiological embedding of early life stress and attendant psychopathology. This preregistered, data-driven study used latent transition analysis (LTA) to identify (1) latent profiles of neural function during a WM and implicit ER task, (2) transitions in profiles across 24 months, and 3) associations between transitions, parental support, and subsequent psychopathology. Using two waves of data from the ABCD Study (Mage T1 = 10; Mage T2 = 12), we found three unique profiles of neural function at both T1 and T2. The Typical, Emotion Hypo-response, and Emotion-Hyper response profiles were characterized by, respectively: moderate amygdala activation and fusiform deactivation; high ACC, fusiform, and insula deactivation; and high amygdala, ACC, and insula response to ER. While 69.5 % remained in the Typical profile from T1 to T2, 27.8 % of the sample moved from one profile at T1 to another at T2. However, neither latent profiles nor transitions exhibited associations between parental support or psychopathology symptoms.

Use of an Allogeneic Leukemia-Derived Dendritic Cell Vaccine in MRD+ AML-Patients Results in MRD Conversion, Improved Relapse-Free Survival and Vaccine Induced Immune Responses to Tumor Antigens

Background. Maintenance therapy in AML patients with measurable residual disease (MRD) remains challenging. Immunotherapy could be an effective way to induce durable disease control. This phase II study aims to show efficacy of priming the immune system, using an allogenic leukemia-derived dendritic cell vaccine (DCP-001), to induce an effective anti-leukemic response to control or kill remaining malignant cells (ADVANCE-II, Clintrials.gov: NCT03697707). Methods. A total of 20 evaluable AML patients in first complete remission (CR1) with MRD positivity and ineligible for HSCT received 4 biweekly doses of 25e6 or 50e6 cells per intradermal vaccination (cells/vc) and 2 doses as boosts at week 14 and 18 of 10e6 cells/vc. MRD, as primary endpoint, was assessed at baseline, week 14, 20 and 32 by flow cytometry and/or molecular analyses. Evaluation of secondary endpoints relapse-free (RFS) and overall survival (OS) was done at data cut-off (18th July 2022). Peripheral blood samples were taken before and during treatment for analysis of vaccine induced responses as measured by IFNγ ELISPOT and general immune profiles by flow cytometry using a 40-marker panel. Results. Patients aged 34-79 (median 60y) had a cytogenetic risk status assessed of 4 better, 15 intermediate and 1 poor-risk, with mutations in NPM1 (n=10), CBFB-MYH11 (n=4), IDH2 (n=2), RUNX1-RUNX1T1 (n=2), TP53 (n=1) and CEBPA (n=1). All 20 patients have received 4 initial vaccinations, 17 patients received all booster vaccinations and 1 patient received one booster. No serious adverse events (AE) or severe AE (grade 3 or higher) related to the treatment have been reported. Related AEs are mainly injection site reactions, such as redness, warmth and swelling, occurring within 48 hours after intradermal administration. To date, median RFS and OS have not yet been reached (Figure 1), with a median follow up period of 15.4 (range 6.6- 16.8) months for the entire study population. Estimated RFS and OS at 6 months is 83.9% (range 64-94%) and 97% (range 79-99%), respectively. Estimated RFS and OS at 12 months is 70% (range 48-85%) and 87% (67-95%), respectively. MRD response (conversion or >10-fold decrease of MRD) was observed in 7 patients: 5 patients converted to negative and 2 showed a MRD decrease. Responses were observed within 14-20 weeks and durable in 4 out of 5 patients, remaining MRD negative up to week 32. Seven patients remained in CR with stable MRD levels and 6 patients relapsed before week 32. Three patients with stable MRD became eligible for HSCT during study and were transplanted successfully. Immune responses were observed to tumor associated antigens expressed by DCP-001; WT1, RHAMM and PRAME, with specific vaccine induced responses (VIR) in the majority of patients (17/20) and highest number of VIR per antigen observed in patients with MRD responses (Figure 2). Differences in immune profiles at baseline were observed; relapsed patients had a high number of CD8RO+ cells, in particular CD8 CM. On the contrary, MRD responders had the highest level of CD8RA+ cells at baseline, with CD8 EMRA cells at the highest level. Patients with stable MRD had comparable, but slightly lower CD8RO+ levels than MRD responders. Conclusion/discussion. Vaccination with DCP-001 resulted in durable MRD responses with five patients converting to MRD negativity, remaining relapse-free and alive during follow up. This translates in promising survival data with the median RFS for the full patient population not reached to date, at a median FU time of 15.4 months. Highest level of vaccine-induced T-cell responses to leukemia specific antigens were detected in MRD responders. Baseline levels of CD8 memory profiles were markedly different in MRD responders, which might be indicative that lower number of memory cells, and thus especially higher number of CD8 EMRA could reflect the ability to induce a tumor specific cytotoxic T-cell response after vaccination. Relapse on study was limited, with an estimated RFS at 6 months of 83.7%, which is higher than expected for this MRD+ AML patient population, which would be around 45% as shown for placebo-treated patients from a recent phase III study in a similar patient population (Quazar AML001). Immunotherapy with DCP-001 as AML maintenance therapy is safe and effective in triggering immune responses and converting patients from MRD positive to MRD negative, leading to promising relapse-free survival. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Monocrotaline induces acutely cerebrovascular lesions, astrogliosis and neuronal degeneration associated with behavior changes in rats: A model of vascular damage in perspective

Pyrrolizidine alkaloids (PAs) are secondary plant metabolites playing an important role as phytotoxins in the plant defense mechanisms and can be present as contaminant in the food of humans and animals. The PA monocrotaline (MCT), one of the major plant derived toxin that affect humans and animals, is present in a high concentration in Crotalaria spp. (Leguminosae) seeds and can induce toxicity after consumption, characterized mainly by hepatotoxicity and pneumotoxicity. However, the effects of the ingestion of MCT in the central nervous system (CNS) are still poorly elucidated. Here we investigated the effects of MCT oral acute administration on the behavior and CNS toxicity in rats. Male adult Wistar were treated with MCT (109 mg/Kg, oral gavage) and three days later the Elevated Pluz Maze test demonstrated that MCT induced an anxiolytic-like effect, without changes in novelty habituation and in operational and spatial memory profiles. Histopathology revealed that the brain of MCT-intoxicated animals presented hyperemic vascular structures in the hippocampus, parahippocampal cortex and neocortex, mild perivascular edema in the neocortex, hemorrhagic focal area in the brain stem, hemorrhage and edema in the thalamus. MCT also induced neurotoxicity in the cortex and hippocampus, as revealed by Fluoro Jade-B and Cresyl Violet staining, as well astrocyte reactivity, revealed by immunocytochemistry for glial fibrillary acidic protein. Additionally, it was demonstrated by RT-qPCR that MCT induced up-regulation on mRNA expression of neuroinflammatory mediator, especially IL1β and CCL2 in the hippocampus and cortex, and down-regulation on mRNA expression of neurotrophins HGDF and BDNF in the cortex. Together, these results demonstrate that the ingestion of MCT induces cerebrovascular lesions and toxicity to neurons that are associated to astroglial cell response and neuroinflammation in the cortex and hippocampus of rats, highlighting CNS damages after acute intoxication, also putting in perspective it uses as a model for cerebrovascular damage.

Virtual Reality Technology in Cognitive Rehabilitation Application: Bibliometric Analysis.

In recent years, with the development of computer science and medical science, virtual reality (VR) technology has become a promising tool for improving cognitive function. Research on VR-based cognitive training has garnered increasing attention. This study aimed to investigate the application status, research hot spots, and emerging trends of VR in cognitive rehabilitation over the past 20 years. Articles on VR-based cognitive rehabilitation from 2001 to 2021 were retrieved from the Web of Science Core Collection. CiteSpace software was used for the visual analysis of authors and countries or regions, and Scimago Graphica software was used for the geographic visualization of published countries or regions. Keywords were clustered using the gCLUTO software. A total of 1259 papers were included. In recent years, research on the application of VR in cognitive rehabilitation has been widely conducted, and the annual publication of relevant literature has shown a positive trend. The main research areas include neuroscience and neurology, psychology, computer science, and rehabilitation. The United States ranked first with 328 papers, and Italy ranked second with 140 papers. Giuseppe Riva, an Italian academic, was the most prolific author with 29 publications. The most frequently cited reference was "Using Reality to Characterize Episodic Memory Profiles in Amnestic Mild Cognitive Impairment and Alzheimer's Disease: Influence of Active and Passive Encoding." The most common keywords used by researchers include "virtual reality," "cognition," "rehabilitation," "performance," and "older adult." The largest source of research funding is from the public sector in the United States. The bibliometric analysis provided an overview of the application of VR in cognitive rehabilitation. VR-based cognitive rehabilitation can be integrated into multiple disciplines. We conclude that, in the context of the COVID-19 pandemic, the development of VR-based telerehabilitation is crucial, and there are still many problems that need to be addressed, such as the lack of consensus on treatment methods and the existence of safety hazards.

Recognition of mRNA Splice Variant and Secretory Granule Epitopes by CD4+ T Cells in Type 1 Diabetes.

A recent discovery effort resulted in identification of novel splice variant and secretory granule antigens within the HLA class I peptidome of human islets and documentation of their recognition by CD8+ T cells from peripheral blood and human islets. In the current study, we applied a systematic discovery process to identify novel CD4+ T cell epitopes derived from these candidate antigens. We predicted 145 potential epitopes spanning unique splice junctions and within conventional secretory granule antigens and measured their invitro binding to DRB1*04:01. We generated HLA class II tetramers for the 35 peptides with detectable binding and used these to assess immunogenicity and isolate T cell clones. Tetramers corresponding to peptides with verified immunogenicity were then used to label T cells specific for these putative epitopes in peripheral blood. T cells that recognize distinct epitopes derived from a cyclin I splice variant, neuroendocrine convertase 2, and urocortin-3 were detected at frequencies that were similar to those of an immunodominant proinsulin epitope. Cells specific for these novel epitopes predominantly exhibited a Th1-like surface phenotype. Among the three epitopes, responses to the cyclin I peptide exhibited a distinct memory profile. Responses to neuroendocrine convertase 2 were detected among pancreatic infiltrating T cells. These results further establish the contribution of unconventional antigens to the loss of tolerance in autoimmune diabetes.

Characteristic columnar connectivity caters to cortical computation: Replication, simulation, and evaluation of a microcircuit model.

The neocortex, and with it the mammalian brain, achieves a level of computational efficiency like no other existing computational engine. A deeper understanding of its building blocks (cortical microcircuits), and their underlying computational principles is thus of paramount interest. To this end, we need reproducible computational models that can be analyzed, modified, extended and quantitatively compared. In this study, we further that aim by providing a replication of a seminal cortical column model. This model consists of noisy Hodgkin-Huxley neurons connected by dynamic synapses, whose connectivity scheme is based on empirical findings from intracellular recordings. Our analysis confirms the key original finding that the specific, data-based connectivity structure enhances the computational performance compared to a variety of alternatively structured control circuits. For this comparison, we use tasks based on spike patterns and rates that require the systems not only to have simple classification capabilities, but also to retain information over time and to be able to compute nonlinear functions. Going beyond the scope of the original study, we demonstrate that this finding is independent of the complexity of the neuron model, which further strengthens the argument that it is the connectivity which is crucial. Finally, a detailed analysis of the memory capabilities of the circuits reveals a stereotypical memory profile common across all circuit variants. Notably, the circuit with laminar structure does not retain stimulus any longer than any other circuit type. We therefore conclude that the model's computational advantage lies in a sharper representation of the stimuli.

Fine‐Grained Memory Profiling of GPGPU Kernels

AbstractMemory performance is a crucial bottleneck in many GPGPU applications, making optimizations for hardware and software mandatory. While hardware vendors already use highly efficient caching architectures, software engineers usually have to organize their data accordingly in order to efficiently make use of these, requiring deep knowledge of the actual hardware. In this paper we present a novel technique for fine‐grained memory profiling that simulates the whole pipeline of memory flow and finally accumulates profiling values in a way that the user retains information about the potential region in the GPU program by showing these values separately for each allocation. Our memory simulator turns out to outperform state‐of‐the‐art memory models of NVIDIA architectures by a magnitude of 2.4 for the L1 cache and 1.3 for the L2 cache, in terms of accuracy. Additionally, we find our technique of fine grained memory profiling a useful tool for memory optimizations, which we successfully show in case of ray tracing and machine learning applications.

On the evaluation of general sparse hybrid linear solvers

AbstractGeneral sparse hybrid solvers are commonly used kernels for solving wide range of scientific and engineering problems. This work addresses the current problems of efficiently solving general sparse linear equations with direct/iterative hybrid solvers on many core distributed clusters. We briefly discuss the solution stages of Maphys, HIPS, and PDSLin hybrid solvers for large sparse linear systems with their major algorithmic differences. In this category of solvers, different methods with sophisticated preconditioning algorithms are suggested to solve the trade off between memory and convergence. Such solutions require a certain hierarchical level of parallelism more suitable for modern supercomputers that allow to scale for thousand numbers of processors using Schur complement framework. We study the effect of reordering and analyze the performance, scalability as well as memory for each solve phase of PDSLin, Maphys, and HIPS hybrid solvers using large set of challenging matrices arising from different actual applications and compare the results with SuperLU_DIST direct solver. We specifically focus on the level of parallel mechanisms used by the hybrid solvers and the effect on scalability. Tuning and Analysis Utilities (TAU) is employed to assess the efficient usage of heap memory profile and measuring communication volume. The tests are run on high performance large memory clusters using up to 512 processors.

Random walks with memory profile of the κ-exponential: a first measurement of diffusive regimes

A new class of random walks, Elephant Random Walks (ERW) in the memory type, non-Markovian, was proposed by Schütz and Trimper characterized by diffusive regimes typical of anomalous diffusion. Following this line, we proposed a model of random walks guided by the principle of kinetic interaction (KIP), where, according to KIP, the temporal evolution of the distribution function of identical particles subject to binary collisions leads us to an ever-increasing functional with time, satisfying the statement of the irreversibility of the second law of Thermodynamics. We derived a distribution of the exponential that is discrete. In the limit , the distribution of the -exponential falls into the ordinary exponential distribution, where we found the typical Brownian diffusion. In the upper limit of anti-equilibrium ( ), we found a transition from the ordinary diffusive regime to the super-diffusive regime. Additionally, moving away from the anti-equilibrium region, we found the ERW’s diffusive behavior. Our results are yet another case of anomalous transport in complex systems, which are associated with particle diffusion for which the variance spreads non-linearly with time.