Multi-level, forming and filament free, bulk switching trilayer RRAM for neuromorphic computing at the edge.

CMOS-RRAM integration holds great promise for low energy and high throughput neuromorphic computing. However, most RRAM technologies relying on filamentary switching suffer from variations and noise, leading to computational accuracy loss, increased energy consumption, and overhead by expensive program and verify schemes. We developed a filament-free, bulk switching RRAM technology to address these challenges. We systematically engineered a trilayer metal-oxide stack and investigated the switching characteristics of RRAM with varying thicknesses and oxygen vacancy distributions to achieve reliable bulk switching without any filament formation. We demonstrated bulk switching at megaohm regime with high current nonlinearity, up to 100 levels without compliance current. We developed a neuromorphic compute-in-memory platform and showcased edge computing by implementing a spiking neural network for an autonomous navigation/racing task. Our work addresses challenges posed by existing RRAM technologies and paves the way for neuromorphic computing at the edge under strict size, weight, and power constraints.

Features of virtual reality impact effectiveness of VR pain alleviation therapeutics in pediatric burn patients: A randomized clinical trial.

Key features of virtual reality (VR) that impact the effectiveness of pain reduction remain unknown. We hypothesized that specific features of the VR experience significantly impact VR's effectiveness in reducing pain during pediatric burn dressing care. Our randomized controlled trial included children 6 to 17 years (inclusive) who were treated in the outpatient clinic of an American Burn Association-verified pediatric burn center. Participants were randomly assigned (1:1:1) to active VR (playing the VR), passive VR (immersed in the same VR environment without interactions), or standard-of-care. On a scale from 0 to 100, participants rated overall pain (primary outcome) and features of the VR experience (game realism, fun, and engagement). Path analysis assessed the interrelationships among these VR key features and their impact on self-reported pain scores. From December 2016 to January 2019, a total of 412 patients were screened for eligibility, and 90 were randomly assigned (31 in the active VR group, 30 in the passive VR group, and 29 in the standard-of-care group). The current study only included those in the VR groups. The difference in median scores of VR features was not statistically significant between the active (realism, 77.5 [IQR: 50-100]; fun, 100 [IQR: 81-100]; engagement, 90 [IQR: 70-100]) and passive (realism, 72 [IQR: 29-99]; fun, 93.5 [IQR: 68-100]; engagement, 95 [IQR: 50-100]) VR distraction types. VR engagement had a significant direct (-0.39) and total (-0.44) effect on self-reported pain score (p<0.05). Key VR features significantly impact its effectiveness in pain reduction. The path model suggested an analgesic mechanism beyond distraction. Differences in VR feature scores partly explain active VR's more significant analgesic effect than passive VR. Trial Registration: ClinicalTrials.gov Identifier: NCT04544631.

Parametric exploration of cellular swelling in a computational model of cortical spreading depression.

Cortical spreading depression (CSD) is a slowly propagating wave of depolarization of brain cells, followed by temporary silenced electrical brain activity. Major structural changes during CSD are linked to neuronal and possibly glial swelling. However, basic questions still remain unanswered. In particular, there are open questions regarding whether neurons or glial cells swell more, and how the cellular swelling affects the CSD wave propagation.In this study, we computationally explore how different parameters affect the swelling of neurons and astrocytes (starshaped glial cells) during CSD and how the cell swelling alters the CSD wave spatial distribution. We apply a homogenized mathematical model that describes electrodiffusion in the intraand extracellular space, and discretize the equations using a finite element method. The simulations are run with a twocompartment (extracellular space and neurons) and a threecompartment version of the model with astrocytes added. We consider cell swelling during CSD in four scenarios: (A) incorporating aquaporin-4 channels in the astrocytic membrane, (B) increasing the neuron/astrocyte ratio to 2:1, (C) blocking and increasing the Na+/K+-ATPase rate in the astrocytic compartment, and (D) blocking the Cl- channels in astrocytes. Our results show that increasing the water permeability in the astrocytes results in a higher astrocytic swelling and a lower neuronal swelling than in the default case. Further, elevated neuronal density increases the swelling in both neurons and astrocytes. Blocking the Na+/K+-ATPase in the astrocytes leads to an increased wave width and swelling in both compartments, which instead decreases when the pump rate is raised. Blocking the Cl- channels in the astrocytes results in neuronal swelling, and a shrinkage in the astrocytes. Our results suggest a supporting role of astrocytes in preventing cellular swelling and CSD, as well as highlighting how dysfunctions in astrocytes might elicit CSD.