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The USA and UK governmental and academic agencies suggest that up to 35% of dementia cases are preventable. We canvassed dementia risk and protective factor awareness among New Zealand older adults to inform the design of a larger survey.
The modified Lifestyle for Brain Health scale quantifying dementia risk was introduced to a sample of 304 eligible self-selected participants.
Two hundred and sixteen older adults (≥50 years), with mean ± standard deviation age 65.5 ± 11.4 years (50–93 years), completed the survey (71% response rate). Respondents were mostly women (n = 172, 80%), European (n = 207, 96%), and well educated (n = 100, 46%, with a tertiary qualification; including n = 17, 8%, with a postgraduate qualification). Around half of the participants felt that they were at a future risk of living with dementia (n = 101, 47%), and the majority felt that this would change their lives significantly (n = 205, 95%), that lifestyle changes would reduce their risk (n = 197, 91%), and that they could make the necessary changes (n = 189, 88%) and wished to start changes soon (n = 160, 74%). Only 4 of 14 modifiable risk or protective factors for dementia were adequately identified by the participants: physical exercise (81%), depression (76%), brain exercises (75%), and social isolation (83%). Social isolation was the commonly cited risk factor for dementia, while physical exercise was the commonly cited protective factor. Three clusters of brain health literacy were identified: psychosocial, medical, and modifiable.
The older adults in our study are not adequately knowledgeable about dementia risk and protective factors. However, they report optimism about modifying risks through lifestyle interventions.
Individual differences in cognitive responses to trauma may represent modifiable risk factors that could allow early identification, targeted early treatment and possibly prevention of chronic posttraumatic stress disorder (PTSD). Ehlers and Clark's cognitive model of PTSD suggests that negative appraisals, disjointed trauma memories, and unhelpful coping strategies maintain PTSD. These are thought to be influenced by cognitive processing during trauma. The aim of this study was to test this model prospectively with path analyses.
Participants (N = 828) were recruited from an emergency department following injury in a violent assault or road traffic collision and 700 participated in the 6-month assessments. Cognitive processing was assessed shortly after the event, negative appraisals, disjointed memories, and unhelpful coping strategies at 1 month, persistent PTSD symptom severity at 6 months, and early PTSD symptom severity at 2 weeks.
Cognitive variables, with trauma type and gender, explained 52% of the variance in PTSD symptom severity at 6 months. Including early symptom severity in the model did not explain more variance (53%). Early PTSD symptom severity, with trauma type and gender, only predicted 40%. Negative appraisals and disjointed memories predicted persistent symptom severity both directly and indirectly via unhelpful strategies. Peritraumatic processing predicted persistent symptom severity mainly indirectly. The effects of trauma type and gender were fully mediated by the cognitive factors.
The results are consistent with theoretically derived predictions and support cognitive factors as indicators of risk for chronic PTSD and as a target for the treatment and prevention of PTSD.
In this paper, I review three ‘anomalies’ or disorders in autobiographical memory: neurological retrograde amnesia (RA), spontaneous confabulation, and psychogenic amnesia.
Existing theories are reviewed, their limitations considered, some of my own empirical findings briefly described, and possible interpretations proposed and interspersed with illustrative case-reports.
In RA, there may be an important retrieval component to the deficit, and factors at encoding may give rise to the relative preservation of early memories (and the reminiscence bump) which manifests as a temporal gradient. Spontaneous confabulation appears to be associated with a damaged ‘filter’ in orbitofrontal and ventromedial frontal regions. Consistent with this, an empirical study has shown that both the initial severity of confabulation and its subsequent decline are associated with changes in the executive function (especially in cognitive estimate errors) and inversely with the quantity of accurate autobiographical memories retrieved. Psychogenic amnesia can be ‘global’ or ‘situation-specific’. The former is associated with a precipitating stress, depressed mood, and (often) a past history of a transient neurological amnesia. In these circumstances, frontal control mechanisms can inhibit retrieval of autobiographical memories, and even the sense of ‘self’ (identity), while compromised medial temporal function prevents subsequent retrieval of what occurred during a ‘fugue’. An empirical investigation of psychogenic amnesia and some recent imaging studies have provided findings consistent with this view.
Taken together, these various observations point to the importance of frontal ‘control’ systems (in interaction with medial temporal/hippocampal systems) in the retrieval and, more particularly, the disrupted retrieval of ‘old’ memories.
Phase-change materials (PCMs) have demonstrated a wide range of potential applications ranging from electronic memories to photonic devices. These applications are enabled by the unconventional portfolio of properties that characterizes crystalline PCMs. Here, we address the origin of these unusual properties and how they are related to the application potential of these materials. Evidence will be presented that the properties are related to an unconventional bonding mechanism. Employing a novel map, which separates solids according to the number of electrons transferred and shared between adjacent atoms, it is shown that PCMs occupy a well-defined region. Depicting physical properties such as the optical dielectric constant as the third dimension in the map reveals systematic property trends. Such trends can be utilized to unravel the origins of the unconventional materials properties or alternatively, as a means to optimize them.
High-current switching performance of ovonic threshold switching (OTS) selectors have successfully enabled the commercialization of high-density three-dimensional (3D) stackable phase-change memory in Intel’s 3D Xpoint technology. This bridges the huge performance gap between dynamic random access memory (DRAM) and Flash. Similar to phase-change memory, OTS uses chalcogenide-based materials, but whereas phase-change memory reversibly switches between a high-resistance amorphous phase and a low-resistance crystalline phase, OTS freezes in the amorphous phase. In this article, we review recent developments in OTS materials and their performance in devices, especially current density and selectivity. Advantages and challenges of OTS devices in the integration with the phase-change memory are discussed. We introduce the evolution of theoretical models for explaining the OTS behavior, including thermal runaway, field-induced nucleation, and generation/recombination of charge carriers.
The rapidly growing demand for data storage and processing, driven by artificial intelligence (AI) and other data-intensive applications, is posing a serious challenge for current computing devices based on the von Neumann architecture. For every calculation, data sets need to be shuffled sequentially between the processor, and multiple memory and storage units through bandwidth-limited and energy-inefficient interconnects, typically causing 40% power wastage. Phase-change materials (PCMs) show great promise to break this bottleneck by enabling nonvolatile memory devices that can optimize the complex memory hierarchy, and neuro-inspired computing devices that can unify computing with storage in memory cells. The articles in this issue of MRS Bulletin highlight recent breakthroughs in the fundamental materials science, as well as electronic and photonic implementations of these novel devices based on PCMs.
The exploitation of phase-change materials (PCMs) in diverse technological applications can be greatly aided by a better understanding of the microscopic origins of their functional properties. Over the last decade, simulations based on electronic-structure calculations within density functional theory (DFT) have provided useful insights into the properties of PCMs. However, large simulation cells and long simulation times beyond the reach of DFT simulations are needed to address several key issues of relevance for the performance of devices. One way to overcome the limitations of DFT methods is to use machine learning (ML) techniques to build interatomic potentials for fast molecular dynamics simulations that still retain a quasi-ab initio accuracy. Here, we review the insights gained on the functional properties of the prototypical PCM GeTe by harnessing such interatomic potentials. Applications and future challenges of the ML techniques in the study of PCMs are also outlined.
The cycling endurance of phase-change memory is one of the last hurdles to overcome to enable its adoption in the larger market for persistent memory products. Phase-change memory cycling endurance failures, whether they are stuck-SET (caused by elemental segregation) or stuck-RESET (caused by void formation), are caused by atomic migration. Various driving forces responsible for the atomic migration have been identified, such as hole-wind force, electrostatic force, and crystallization-induced segregation. We introduce several strategies to improve cycling endurance based on an understanding of driving forces and interactions among them. Utilizing some of these endurance-improving techniques, record-high phase-change memory cycling endurance at around 1012 cycles has been recently reported using a confined phase-change memory cell with a metallic liner.
Driven by the rapid rise of silicon photonics, optical signaling is moving from the realm of long-distance communications to chip-to-chip, and even on-chip domains. If on-chip signaling becomes optical, we should consider what more we might do with light than just communicate. We might, for example, set goals for the storing and processing of information directly in the optical domain. Doing this might enable us to supplement, or even surpass, the performance of electronic processors, by exploiting the ultrahigh bandwidth and wavelength division multiplexing capabilities offered by optics. In this article, we show how, by using an integrated photonics platform that embeds chalcogenide phase-change materials into standard silicon photonics circuits, we can achieve some of these goals. Specifically, we show that a phase-change integrated photonics platform can deliver binary and multilevel memory, arithmetic and logic processing, as well as synaptic and neuronal mimics for use in neuromorphic, or brain-like, computing—all working directly in the optical domain.
This chapter seeks to extend previous studies of Charles Babbage’s celebrated difference engine through an examination of a rare surviving fragment in the Whipple Museum’s collection. Constructed from scrap parts inherited by Charles’s son, Henry, in order to relaunch the engine project, the fragment has much to reveal about the afterlife of Babbage’s most famous failure. An appendix to the chapter also publishes for the first time key documents relating to Henry Babbage’s project.
This chapter discusses whether and in what respects patients who experience intraoperative awareness with recall can be harmed by it. The chapter considers psychological and pharmacological interventions that might prevent, weaken or erase memories of intraoperative awareness. When awareness is detected during surgery, mechanisms of memory encoding and consolidation may be difficult to reverse. Intervening in the brain to erase memories already consolidated is even more difficult. If a patient recalls being aware days or weeks after surgery, then the memory may be resistant to modification. Nevertheless, memory research and actual cases indicate that these memories can be prevented by administering consolidation-blocking drugs to induce anterograde amnesia. It is also theoretically possible for reconsolidation-blocking drugs to induce retrograde amnesia and eliminate memories of awareness.
Previous research has shown that women have an advantage on verbal episodic memory and processing speed tasks, while men show an advantage on spatial ability measures. Previous work has also found differences in cognition across age. The current study examines gender differences in neurocognitive functioning across adulthood, whether age moderates this effect, and whether these differences remain consistent with practice across multiple testing sessions.
Data from the Virginia Cognitive Aging Project were used, which included participants between the ages of 18 and 99 years (N = 5125). Participants completed measures assessing five cognitive domains: episodic memory, processing speed, reasoning, spatial visualization, and vocabulary.
Results showed that gender was significantly related to memory, speed, and spatial visualization, but not to vocabulary or reasoning. Results of invariance analyses across men and women provided evidence of configural and metric invariance, along with partial scalar invariance. Additionally, there was little evidence that age or practice influenced the gender effect on neurocognition.
Consistent with the previous research, these results suggest that there is a female advantage in episodic memory and processing speed, and a male advantage in spatial visualization. Gender was shown to influence cognition similarly across adulthood. Furthermore, the influence of gender remained the same across three sessions, which is consistent with the previous work that has shown that training does not differentially impact performance on spatial ability measures for females compared to males.
Impaired cognitive functioning constitutes an important symptom of major depressive disorder (MDD), potentially associated with elevated cortisol levels. Adverse childhood experiences (ACE) enhance the risk for MDD and can contribute to disturbances in the stress systems, including cortisol and cognitive functions. In healthy participants, cortisol administration as well as acute stress can affect cognitive performance. In the current study, we tested cognitive performance in MDD patients with (N = 32) and without (N = 52) ACE and healthy participants with (N = 22) and without (N = 37) ACE after psychosocial stress induction (Trier Social Stress Test, TSST) and a control condition (Placebo-TSST). MDD predicted lower performance in verbal learning and both selective and sustained attention, while ACE predicted lower performance in psychomotoric speed and working memory. There were no interaction effects of MDD and ACE. After stress, MDD patients were more likely to show lower performance in working memory as well as in selective and sustained attention compared with participants without MDD. Individuals with ACE were more likely to show lower performance in verbal memory after stress compared with individuals without ACE. Our results indicate negative effects of MDD and ACE on distinct cognitive domains. Furthermore, MDD and/or ACE seem to enhance susceptibility for stress-related cognitive impairments.
In this chapter I present the received view in the epistemology of memory, according to which one only knows p via memory if one knew p at an earlier time. I discuss Jennifer Lackey's counterexamples to this view and address Thomas Señor's criticisms to Lackey's cases. I explain why factual-defeater-based cases of mnemonic knowledge from non-knowledge should not be expected.
In this chapter I pull together the threads of discussion of the previous chapters to examine the different ways knowledge from non-knowledge may arise in the epistemologies of inference, testimony and memory. I offer a defeater-based explanatory framework for the various forms this phenomenon takes in the context of the three different epistemic sources and draw some conclusions about the picture that emerges.