Current Stimulus Research Articles

Heterogeneous Forgetting Rates and Greedy Allocation in Slot-Based Memory Networks Promotes Signal Retention.

A key question in the neuroscience of memory encoding pertains to the mechanisms by which afferent stimuli are allocated within memory networks. This issue is especially pronounced in the domain of working memory, where capacity is finite. Presumably the brain must embed some "policy" by which to allocate these mnemonic resources in an online manner in order to maximally represent and store afferent information for as long as possible and without interference from subsequent stimuli. Here, we engage this question through a top-down theoretical modeling framework. We formally optimize a gating mechanism that projects afferent stimuli onto a finite number of memory slots within a recurrent network architecture. In the absence of external input, the activity in each slot attenuates over time (i.e., a process of gradual forgetting). It turns out that the optimal gating policy consists of a direct projection from sensory activity to memory slots, alongside an activity-dependent lateral inhibition. Interestingly, allocating resources myopically (greedily with respect to the current stimulus) leads to efficient utilization of slots over time. In other words, later-arriving stimuli are distributed across slots in such a way that the network state is minimally shifted and so prior signals are minimally "overwritten." Further, networks with heterogeneity in the timescales of their forgetting rates retain stimuli better than those that are more homogeneous. Our results suggest how online, recurrent networks working on temporally localized objectives without high-level supervision can nonetheless implement efficient allocation of memory resources over time.

Neurocognitive Targets for Psychological Assistance in Patients with the Anhedonia Phenomenon within the Framework of Affective Pathology

IntroductionAnhedonia is a transdiagnostic psychopathological phenomenon that is considered a key feature for several disorders, primarily affective spectrum disorders. It exhibits a significant association with social and occupational maladjustment, reduced quality of life, and increased suicidal risk among psychiatric patients.ObjectivesThe aim of this study is to identify recommendations for psychotherapeutic assistance for patients with affective spectrum disorders.MethodsA total of 26 patients with affective spectrum disorders (ICD-10 code - F33, F31) and the phenomenon of anhedonia were examined. We utilized neuropsychological methods aimed at investigating a wide range of cognitive functions (Dynamic praxis; Color interference test; Arithmetic Tasks; Number of skips and impulsive errors; Reverse and straight rows; Verbal fluency; Design fluency; Rey-Osterritz figure) and psychometric methods designed to diagnose various types of anhedonia (consummatory (TEPS), anticipatory (TEPS), social (RSAS), and physical (PAS)).Results Among patients with depression, the consummatory type of anhedonia was the most pronounced. A relationship was found between anticipatory anhedonia and phonetic verbal fluency (r = 0.487; p < 0.01). Additionally, there were correlations between immediate (consummatory) pleasure experience and Rey figure errors (r = -0.349; p < 0.05). Social anhedonia was associated with phonetic verbal fluency productivity (r = -0.509; p < 0.01) and performance in visual fluency productivity (r = -0.473; p < 0.01).ConclusionsThe obtained results allow us to hypothesize that anhedonia is associated with difficulties both in evaluating and imagining possible positive stimuli, which leads to a lack of emotional response to the current stimulus. Thus, the availability of current pleasure may be linked to memory accessibility and regulatory function. When these domains are weakened, the respondent loses the ability to associate the current stimulus with positive past experiences, making it challenging to generate an emotional response in the current stimulus situation and disrupting the anticipation of pleasure. Based on the results, we propose the effective use of behavioral activation and work on the actualization of past experiences. Behavioral activation can be implemented by gradually introducing behaviors associated with past pleasures into the patient’s life, followed by cognitive restructuring aimed at focusing the emotional response on past and current stimuli. In addition to this, from a neurocognitive perspective, an additional element of therapy could involve training various types of cognitive functions, with an emphasis on the auditory modality.Disclosure of InterestNone Declared

Comparison of the activation level in the sensorimotor cortex between motor point and proximal nerve bundle electrical stimulation

Objective. Neuromuscular electrical stimulation (NMES) is widely used for motor function rehabilitation in stroke survivors. Compared with the conventional motor point (MP) stimulation, the stimulation at the proximal segment of the peripheral nerve (PN) bundles has been demonstrated to have multiple advantages. However, it is not known yet whether the PN stimulation can increase the cortical activation level, which is crucial for motor function rehabilitation. Approach. The current stimuli were delivered transcutaneously at the muscle belly of the finger flexors and the proximal segment of the median and ulnar nerves, respectively for the MP and PN stimulation. The stimulation intensity was determined to elicit the same contraction levels between the two stimulation methods in 18 healthy individuals and a stroke patient. The functional near-infrared spectroscopy and the electromyogram were recorded to compare the activation pattern of the sensorimotor regions and the target muscles. Main Results. For the healthy subjects, the PN stimulation induced significantly increased concentration of the oxygenated hemoglobin in the contralateral sensorimotor areas, and enhanced the functional connectivity between brain regions compared with the MP stimulation. Meanwhile, the compound action potentials had a smaller amplitude and the H-reflex became stronger under the PN stimulation, indicating that more sensory axons were activated in the PN stimulation. For the stroke patient, the PN stimulation can elicit finger forces and induce activation of both the contralateral and ipsilateral motor cortex. Conclusions. Compared with the MP stimulation, the PN stimulation can induce more cortical activation in the contralateral sensorimotor areas possibly via involving more activities in the central pathway. Significance. This study demonstrated the potential of the PN stimulation to facilitate functional recovery via increasing the cortical activation level, which may help to improve the outcome of the NMES-based rehabilitation for motor function recovery after stroke.

A numerical study of a single isolated human ventricular cell response to a periodic pulse stimulus current using the Rogers–McCulloch model

Among the primary causes of cardiac arrhythmias are abnormalities in the generation of action potentials (APs) by the cardiac cells, which may be induced by alterations in the electrophysiological properties of the cells as well as the stimuli delivered to them. Through numerical simulations using the phenomenological model of Rogers–McCulloch, this study examined how external stimuli modulate the electrical activity of a single isolated human ventricular cell functioning under normal conditions. First, we investigated how the initial conditions of the two model state variables affect how the cell responds to a single rectangular current pulse. This allows for the determination of a critical curve, which separates the initial conditions that allow for AP activation from those that inhibit it. This critical curve can be used to predict AP activation not only when the cell is stimulated by a single current pulse but also by a periodic stimulus. Then, we examined the cell response to a periodic train of rectangular current pulses, with a focus on the effects of the stimulus pacing length and amplitude. Our findings demonstrated that, despite not considering any alteration in the dynamics of ionic currents through the cell membrane, the Rogers–McCulloch model was capable of reproducing some of the most common activation patterns that have been widely identified in several clinical, experimental, and numerical studies. Depending on the stimulus properties, the following activation patterns were identified: (1) AP activation in synchrony with the stimulus, with one AP activation per pulse; (2) quasi-periodic and periodic Wenckebach-like patterns, in which successive AP activations are interrupted by a skipped beat; (3) completely irregular patterns; (4) abnormal potential oscillations that interrupt the repolarization of a previously activated AP, followed or not by a skipped beat; and (5) abnormal potential oscillations that completely inhibit cell repolarization.

Characterization and closed-loop control of infrared thalamocortical stimulation produces spatially constrained single-unit responses.

Deep brain stimulation (DBS) is a powerful tool for the treatment of circuitopathy-related neurological and psychiatric diseases and disorders such as Parkinson's disease and obsessive-compulsive disorder, as well as a critical research tool for perturbing neural circuits and exploring neuroprostheses. Electrically mediated DBS, however, is limited by the spread of stimulus currents into tissue unrelated to disease course and treatment, potentially causing undesirable patient side effects. In this work, we utilize infrared neural stimulation (INS), an optical neuromodulation technique that uses near to midinfrared light to drive graded excitatory and inhibitory responses in nerves and neurons, to facilitate an optical and spatially constrained DBS paradigm. INS has been shown to provide spatially constrained responses in cortical neurons and, unlike other optical techniques, does not require genetic modification of the neural target. We show that INS produces graded, biophysically relevant single-unit responses with robust information transfer in rat thalamocortical circuits. Importantly, we show that cortical spread of activation from thalamic INS produces more spatially constrained response profiles than conventional electrical stimulation. Owing to observed spatial precision of INS, we used deep reinforcement learning (RL) for closed-loop control of thalamocortical circuits, creating real-time representations of stimulus-response dynamics while driving cortical neurons to precise firing patterns. Our data suggest that INS can serve as a targeted and dynamic stimulation paradigm for both open and closed-loop DBS.

Response boosts serial dependence in the numerosity estimation task

Perceptions of current stimuli are sometimes biased toward or away from past perceptions. This phenomenon is called serial dependence. However, the strength of the effect of past responses on serial dependence has not been fully elucidated. We conducted experiments with a task in which participants estimated the number of dot arrays (numerosity estimation task) and directly compared whether the strength of serial dependence changed in the numerosity estimation task when participants responded or did not respond in the immediately preceding trial. We also examined whether the strength of serial dependence affected the accuracy of the numerosity estimation. We found that attractive serial dependence was stronger when participants responded in the immediately preceding trial than when they only saw the stimulus. The results suggest that the information from the previous stimulus must reach the higher-level processes associated with perceptual decisions to influence the estimation of the current stimulus. However, it is possible that the results of this study are specific to tasks in which participants respond with numeric symbols. The magnitude of the serial dependence effect was not observed to affect numerosity estimation performance, and no evidence was found that serial dependence enhances accuracy in the numerosity estimation task.

Effect of epiretinal electrical stimulation on the glial cells in a rabbit retinal eyecup model.

We examined how pulse train electrical stimulation of the inner surface of the rabbit retina effected the resident glial cells. We used a rabbit retinal eyecup preparation model, transparent stimulus electrodes, and optical coherence tomography (OCT). The endfeet of Müller glia processes line the inner limiting membrane (ILM). To examine how epiretinal electrode stimulation affected the Müller glia, we labeled them post stimulation using antibodies against soluble glutamine synthetase (GS). After 5 min 50 Hz pulse train stimulation 30 μm from the surface, the retina was fixed, immunostained for Müller glia, and examined using confocal microscopic reconstruction. Stimulus pulse charge densities between 133-749 μC/cm2/ph were examined. High charge density stimulation (442-749 μC/cm2/ph) caused significant losses in the GS immunofluorescence of the Müller glia endfeet under the electrode. This loss of immunofluorescence was correlated with stimuli causing ILM detachment when measured using OCT. Müller cells show potassium conductances at rest that are blocked by barium ions. Using 30 msec 20 μA stimulus current pulses across the eyecup, the change in transretinal resistance was examined by adding barium to the Ringer. Barium caused little change in the transretinal resistance, suggesting under low charge density stimulus pulse conditions, the Müller cell radial conductance pathway for these stimulus currents was small. To examine how epiretinal electrode stimulation affected the microglia, we used lectin staining 0-4 h post stimulation. After stimulation at high charge densities 749 μC/cm2/ph, the microglia under the electrode appeared rounded, while the local microglia outside the electrode responded to the stimulated retina by process orientation inwards in a ring by 30 min post stimulation. Our study of glial cells in a rabbit eyecup model using transparent electrode imaging suggests that epiretinal electrical stimulation at high pulse charge densities, can injure the Müller and microglia cells lining the inner retinal surface in addition to ganglion cells.

Oculomotor inhibition markers of working memory load.

Involuntary eye movements occur constantly even during fixation and were shown to convey information about cognitive processes. They are inhibited momentarily in response to external stimuli (oculomotor inhibition, OMI), with a time and magnitude that depend on stimulus saliency, attention, and expectations. It was recently shown that the working memory load for numbers modulates the microsaccade rate; however, the generality of the effect and its temporal properties remain unclear. Our goal was to investigate the relationship between OMI and the working memory load for simple colored shapes. Participants (N = 26) maintained their fixation while their eyes were tracked; they viewed briefly flashed colored shapes accompanied by small arrows indicating the shapes to be memorized (1/2/3). After a retention period, a probe shape appeared for matching. The microsaccade rate modulation and temporal properties were analyzed for the memory encoding, maintenance, and retrieval phases. Microsaccade inhibition was stronger when more shapes were memorized, and performance improved when microsaccades were suppressed during maintenance and retrieval. This occurred even though the physical stimuli were identical in number under all conditions. Thus, oculomotor inhibition may play a role in silencing the visual input while processing current stimuli and is generally related to processing time and load.

Emergence of spiral and antispiral patterns and its CGLE analysis in leech-heart interneuron model with electromagnetic induction

Neurons can exhibit various rhythmic activities such as bursting, spiking, and quiescent states when exposed to external input current stimulus. In this paper, a model of medicinal leech's heart (LH) interneuron is considered to describe the dynamics of neurons with a varied range of electrical activities. The crucial insights into the model's dynamics are explored in three different parameter regimes: phasic spiking, regular spiking, and bursting, based upon the codimension-one bifurcation of the model by considering VK2shift as a bifurcation parameter. The spatiotemporal dynamics of the model are explored by allowing 1D and 2D diffusion in the membrane voltage. The 1D diffusive system produces irregular bursting dynamics for the intermediate value of diffusion coefficients, whereas, at higher values, it shows synchronized oscillations. In the presence of 2D diffusion, the emergence of different types of spiral patterns is observed in the system. Furthermore, the system is extended by incorporating electromagnetic induction in the membrane voltage to explore the effect of induction on the various dynamics of neural model. By varying its intensities, the membrane voltage in the extended model produces a variety of discharge modes, such as periodic spiking, fast-spiking, resting, and spike-adding phenomena. In addition, the emergence of anti-spiral patterns in the extended model near subcritical Hopf bifurcation is analytically verified using the complex Ginzburg-Landau equation (CGLE). These findings demonstrate that the firing patterns vary based on the control parameters, and these variations contribute to our understanding of how the brain system transmits and processes the signals.

The effect of bipolar bihemispheric tDCS on executive function and working memory abilities.

Cognitive functioning is central to the ability to learn, problem solve, remember, and use information in a rapid and accurate manner and cognitive abilities are fundamental for communication, autonomy, and quality of life. Transcranial electric stimulation (tES) is a very promising tool shown to improve various motor and cognitive functions. When applied as a direct current stimulus (transcranial direct current stimulation; tDCS) over the dorsolateral pre-frontal cortex (DLPFC), this form of neurostimulation has mixed results regarding its ability to slow cognitive deterioration and potentially enhance cognitive functioning, requiring further investigation. This study set out to comprehensively investigate the effect that anodal and cathodal bipolar bihemispheric tDCS have on executive function and working memory abilities. 72 healthy young adults were recruited, and each participant was randomly allocated to either a control group (CON), a placebo group (SHAM) or one of two neurostimulation groups (Anodal; A-STIM and Cathodal; C-STIM). All participants undertook cognitive tests (Stroop & N Back) before and after a 30-minute stimulation/ sham/ control protocol. Overall, our results add further evidence that tDCS may not be as efficacious for enhancing cognitive functioning as it has been shown to be for enhancing motor learning when applied over M1. We also provide evidence that the effect of neurostimulation on cognitive functioning may be moderated by sex, with males demonstrating a benefit from both anodal and cathodal stimulation when considering performance on simple attention trial types within the Stroop task. Considering this finding, we propose a new avenue for tDCS research, that the potential that sex may moderate the efficacy of neurostimulation on cognitive functioning.

Charge-Mode Neural Stimulator With a Capacitor-Reuse Residual Charge Detector and Active Charge Balancing for Epileptic Seizure Suppression.

This study proposes a charge-mode neural stimulator for electrical stimulation systems that utilizes a capacitor-reuse technique with a residual charge detector and achieves active charge balancing simultaneously. The design is mainly used for epilepsy suppression systems to achieve real-time symptom relief during seizures. A charge-mode stimulator is adopted in consideration of the complexity of circuit design, the high voltage tolerance of transistors, and system integration requirements in the future. The residual charge detector allows users to understand the current stimulus situation, enabling them to make optimal adjustments to the stimulation parameters. On the basis of the information on actual stimulation charge, active charge balancing can effectively prevent the accumulation of mismatched charges on electrode impedance. The capacitor- and phase-reuse techniques help realize high integration of the overall stimulator circuit in consideration of the commonality of the use of a capacitor and charging/discharging phase in the stimulation circuit and charge detector. The proposed charge-mode neural stimulator is implemented in a TSMC 0.18 µm 1P6M CMOS process with a core area of 0.2127 mm2. Measurement results demonstrate the accuracy of the stimulation's functionality and the programmable stimulus parameters. The effectiveness of the proposed charge-mode neural stimulator for epileptic seizure suppression is verified through animal experiments.

Versatile and high-accuracy seq2seq model with self-attention mechanism for Li-ion battery characterization

In this paper, we innovatively propose a seq2seq model that incorporates a self-attention mechanism for modeling the external characteristics of Li-ion batteries.During training, an input sequence of shape (4, time_steps) is formed by concatenating the battery voltage at each time step with the external stimuli such as current, temperature, and cumulative capacity at the next time step. The voltage variation at next step will be used as the target sequence of shape (1, time_steps). During inference, the input sequence is iteratively updated by adding the voltage variation obtained at each step to the previous voltage value, allowing us to predict the voltage variation over the entire time series. The seq2seq model employs two heads that utilize different sequence masks, ensuring attention to both historical data and current stimuli. This approach achieves top-tier prediction accuracy on an open dataset.Furthermore, our model demonstrates outstanding versatility and transferability, as it is not constrained by battery type, operating conditions, temperature, or data upload frequency.Lastly, the characteristics of aged batteries can be represented through fine-tuning.

Designing for sensory adaptation: what you see depends on what you've been looking at - Recommendations, guidelines and standards should reflect this.

Sensory systems continuously recalibrate their responses according to the current stimulus environment. As a result, perception is strongly affected by the current and recent context. These adaptative changes affect both sensitivity (e.g., habituating to noise, seeing better in the dark) and appearance (e.g. how things look, what catches attention) and adjust to many perceptual properties (e.g. from light level to the characteristics of someone's face). They therefore have a profound effect on most perceptual experiences, and on how and how well the senses work in different settings. Characterizing the properties of adaptation, how it manifests, and when it influences perception in modern environments can provide insights into the diversity of human experience. Adaptation could also be leveraged both to optimize perceptual abilities (e.g. in visual inspection tasks like radiology) and to mitigate unwanted consequences (e.g. exposure to potentially unhealthy stimulus environments).

Feedforward connectivity patterns from visual areas to the front of the brain contain information about sensory stimuli regardless of awareness or report

Current theories of consciousness can be categorized to some extent by their predictions about the putative role of the prefrontal cortex (PFC) in conscious perception. One family of the theories proposes that the PFC is necessary for conscious perception. The other postulates that the PFC is not necessary and that other areas (e.g., posterior cortical areas) are more important for conscious perception. No-report paradigms could potentially arbitrate the debate as they disentangle task reporting from conscious perception. While previous no-report paradigms tend to point to a reduction in PFC activity, they have not examined the critical role of the PFC in “monitoring” or “reading out” the patterns of activity in the sensory cortex to generate conscious perception. To address this, we reanalysed electroencephalography (EEG) data from a no-report inattentional blindness paradigm (Shafto & Pitts, 2015). We examined the role of feedforward input patterns to the PFC from sensory cortices. We employed nonparametric spectral Granger causality and quantified the amount of information that reflected the contents of consciousness using multivariate classifiers. Unexpectedly, regardless of whether the stimulus was consciously seen or not, we found that information relating to the current sensory stimulus was present in the pattern of inputs from visual areas to the PFC. In light of these findings, we suggest various theories of consciousness need to be revised to accommodate the fact that the contents of consciousness are decodable from the input patterns from posterior sensory regions to the PFC, regardless of awareness (or report).

Adaptive biasing of action-selective cortical build-up activity by stimulus history.

Decisions under uncertainty are often biased by the history of preceding sensory input, behavioral choices, or received outcomes. Behavioral studies of perceptual decisions suggest that such history-dependent biases affect the accumulation of evidence and can be adapted to the correlation structure of the sensory environment. Here, we systematically varied this correlation structure while human participants performed a canonical perceptual choice task. We tracked the trial-by-trial variations of history biases via behavioral modeling and of a neural signature of decision formation via magnetoencephalography (MEG). The history bias was flexibly adapted to the environment and exerted a selective effect on the build-up (not baseline level) of action-selective motor cortical activity during decision formation. This effect added to the impact of the current stimulus. We conclude that the build-up of action plans in human motor cortical circuits is shaped by dynamic prior expectations that result from an adaptive interaction with the environment.

ApoE variant associated with cognitive resilience alters AD associated hyperexcitability in dentate granule neurons

AbstractBackgroundCognitive decline in Alzheimer’s disease (AD) differs based on background genetics even with similar pathology. Using genetic linkage analysis, we identified a coding variant in the receptor binding domain of ApoE that leads to changes in cognitive performance across a genetically diverse population harboring familial (FAD) mutations known as the AD‐BXDs (Neuner et al., 2019). Using CRISPR‐based gene editing, we developed a C57BL/6J (B6) mouse carrying the ApoE allele from the DBA/2J (D2) strain (ApoEE163D) and determined that ApoEE163D mice with 5XFAD transgene (ApoEE163D‐5XFAD) are susceptible to cognitive decline compared to B6‐5XFAD mice (Kaczorowski, et al., 2022).Analysis of hippocampal RNA sequencing profiles from the hippocampus indicates robust transcriptomic changes in dentate gyrus (DG) granule cells associated with cognitive resilience to FAD mutations in the presence of the B6 ApoE genotype. Here we aim to evaluate the functional implications.MethodWe adapted the Patch‐Seq method (Cadwell et al., 2017) to investigate transcriptional and electrophysiological changes within the DG associated with both FAD mutations and ApoE genotype. Whole‐cell patch clamp was used to evaluate intrinsic excitability of granule cells from 14month old B6 mice carrying FAD mutations and ApoEE163D, compared to age matched controls. The cellular contents, including the nucleus, were collected after each recording to characterize the transcriptome, and the cells were filled and stained for downstream analysis of neuronal morphology.ResultWe observed a significant interaction of the 5XFAD and ApoE genotypes on DG granule cell excitability. Specifically, cells from ApoEE163D‐5XFAD required less current stimulus to both elicit a single action potential, and to fire in response to a current ramp (rheobase). Although input resistance was comparable across all 4 groups, the sag ratio of ApoEE163D‐5XFAD was also reduced.ConclusionEnhancement of DG excitability of ApoEE163D‐5XFAD mice may underlie increased seizure susceptibility that has been reported previously in FAD animal models on D2 genetic background and associated with increased risk of seizures in AD patients. Ongoing work will integrate DG excitability with single‐cell RNAseq, morphology, and behavior to dissect mechanisms underlying the modifier effect of ApoE genotype on susceptibility and resilience to cognitive deficits in FAD mutation carriers.

Ibuprofen modulates tetrodotoxin-resistant persistent Na+ currents at acidic pH in rat trigeminal ganglion neurons

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to relieve various symptoms such as headache, arthralgia, and dental pain. While the primary mechanism of NSAID-based pain relief is the inhibition of cyclooxygenase-2, several NSAIDs also modulate other molecular targets related to nociceptive transmission such as voltage-gated Na+ channels. In the present study, we examined the effects of NSAIDs on persistent Na+ current (INaP) mediated by tetrodotoxin-resistant (TTX-R) Na+ channels in small-to medium-sized trigeminal ganglion neurons using a whole-cell patch-clamp technique. At clinically relevant concentrations, all propionic acid derivatives tested (ibuprofen, naproxen, fenoprofen, and flurbiprofen) preferentially inhibited the TTX-R INaP. The inhibition was more potent at acidic extracellular pH (pH 6.5) than at normal pH (pH 7.4). Other NSAIDs, such as ketorolac, piroxicam, and aspirin, had a negligible effect on the TTX-R INaP. Ibuprofen both accelerated the onset of inactivation and retarded the recovery from inactivation of TTX-R Na+ channels at acidic extracellular pH. However, all NSAIDs tested in this study had minor effects on voltage-gated K+ currents, as well as hyperpolarization-activated and cyclic nucleotide-gated cation currents, at both acidic and normal extracellular pH. Under current-clamp conditions, ibuprofen decreased the number of action potentials elicited by depolarizing current stimuli at acidic (pH 6.5) extracellular pH. Considering that extracellular pH falls as low as 5.5 in inflamed tissues, TTX-R INaP inhibition could be a mechanism by which ibuprofen and propionic acid derivative NSAIDs modulate inflammatory pain.

Minimally Invasive Hypoglossal Nerve Stimulator Enabled by ECG Sensor and WPT to Manage Obstructive Sleep Apnea

A hypoglossal nerve stimulator (HGNS) is an invasive device that is used to treat obstructive sleep apnea (OSA) through electrical stimulation. The conventional implantable HGNS device consists of a stimuli generator, a breathing sensor, and electrodes connected to the hypoglossal nerve via leads. However, this implant is bulky and causes significant trauma. In this paper, we propose a minimally invasive HGNS based on an electrocardiogram (ECG) sensor and wireless power transfer (WPT), consisting of a wearable breathing monitor and an implantable stimulator. The breathing external monitor utilizes an ECG sensor to identify abnormal breathing patterns associated with OSA with 88.68% accuracy, achieved through the utilization of a convolutional neural network (CNN) algorithm. With a skin thickness of 5 mm and a receiving coil diameter of 9 mm, the power conversion efficiency was measured as 31.8%. The implantable device, on the other hand, is composed of a front-end CMOS power management module (PMM), a binary-phase-shift-keying (BPSK)-based data demodulator, and a bipolar biphasic current stimuli generator. The PMM, with a silicon area of 0.06 mm2 (excluding PADs), demonstrated a power conversion efficiency of 77.5% when operating at a receiving frequency of 2 MHz. Furthermore, it offers three-voltage options (1.2 V, 1.8 V, and 3.1 V). Within the data receiver component, a low-power BPSK demodulator was ingeniously incorporated, consuming only 42 μW when supplied with a voltage of 0.7 V. The performance was achieved through the implementation of the self-biased phase-locked-loop (PLL) technique. The stimuli generator delivers biphasic constant currents, providing a 5 bit programmable range spanning from 0 to 2.4 mA. The functionality of the proposed ECG- and WPT-based HGNS was validated, representing a highly promising solution for the effective management of OSA, all while minimizing the trauma and space requirements.

Amyloid-β Effects on Peripheral Nerve: A New Model System.

Although there are many biochemical methods to measure amyloid-β (Aβ)42 concentration, one of the critical issues in the study of the effects of Aβ42 on the nervous system is a simple physiological measurement. The in vitro rat sciatic nerve model is employed and the nerve action potential (NAP) is quantified with different stimuli while exposed to different concentrations of Aβ42. Aβ42 predominantly reduces the NAP amplitude with minimal effects on other parameters except at low stimulus currents and short inter-stimulus intervals. The effects of Aβ42 are significantly concentration-dependent, with a maximum reduction in NAP amplitude at a concentration of 70 nM and smaller effects on the NAP amplitude at higher and lower concentrations. However, even physiologic concentrations in the range of 70 pM did reduce the NAP amplitude. The effects of Aβ42 became maximal 5-8 h after exposure and did not reverse during a 30 min washout period. The in vitro rat sciatic nerve model is sensitive to the effects of physiologic concentrations of Aβ42. These experiments suggest that the effect of Aβ42 is a very complex function of concentration that may be the result of amyloid-related changes in membrane properties or sodium channels.

Neuromorphic behaviors in a neuron circuit based on current-controlled Chua Corsage Memristor

Locally active memristor is considered as an ideal device for building neuron circuits. In this study, a novel current-controlled Chua Corsage Memristor (CCM), which supplements the existing CCM family, is proposed to explore its unknown neuromorphic dynamics. The non-volatility of the current-controlled CCM is verified by its power-off plot and the locally active domain is identified by its DC I-V plot. A third-order neuron circuit is developed by embedding the current-controlled CCM into a passive LC network. The edge of chaos domain of the neuron circuit is identified only by real parts of the eigenvalues of the system's Jacobi matrix. The resulting circuit is capable of sensing external current stimuli and producing neuromorphic behaviors when it is poised on or near the edge of chaos, making it more bionic. The neuromorphic behaviors in four different parameter intervals are revealed in detail, and the generation mechanisms are analyzed based on the theories of Hopf bifurcation and edge of chaos. Due to its simple structure and complex neuromorphic behaviors, it is expected that the neuron circuit may help to further study memristor-based neuron models.