Biology subjects

Bista, S.

Publications and source records attributed to Bista, S..

5 recordsLinked to original sources

bioRxiv2025

Spinal electrophysiology reveals frequency-specific spatial patterns of neural activity and corticospinal coherence during pincer-grip

BackgroundNeural dynamics within sensory-motor networks involved in motor control exhibit well-established frequency-dependent patterns of cortical activity. In contrast, corresponding neural patterns of spinal cord activity remain poorly understood. As an active functional part of motor control, characterising spinal cord activity is essential for understanding sensorimotor function. High-density electrospinography presents a novel technique to assess spinal neural dynamics by non-invasively recording task-relevant electrical activity. ObjectiveTo non-invasively investigate spatio-spectral patterns of task-related spinal activity and its functional connectivity with cortical regions during isometric pincer-grip contraction. MethodologyHere, we simultaneously recorded 128-channel electroencephalography (EEG), 64-channel electrospinography (ESG), and two bipolar electromyography (EMG) signals during an isometric pincer-grip task. Frequency-specific spatial patterns of spinal activity and cortico-spinal connectivity were evaluated by calculating task-related ESG power and cortico-spinal coherence between ESG and EEG signals during the isometric hold. ResultsDistinct frequency-specific spatial patterns of spinal activity were observed at lower cervical levels during sustained hold, with significant activation over the ipsilateral anterolateral region. In the beta band, task-related spinal activity was significantly ipsilateralised, and exhibited significant cortico-spinal connectivity between contralateral motor cortex and ipsi-anterolateral spinal region. ConclusionsThis first-of-its-kind application of HD non-invasive spinal electrophysiology revealed that the spinal cord exhibits distinct frequency-specific spatial activation and cortical connectivity patterns during pincer-grip sustained hold. Specifically, the ipsi-anterolateral spinal region demonstrated high task-relevance, potentially indicating anterior horn activity and its connectivity with motor cortex. Furthermore, beta-band activation was observed as a key signature during sustained hold, further underpinning its relevance during motor control.

neuroscience↗

bioRxiv2024

SC10X/U: A High-density Electrode System for Non-Invasive Recording of Neural Activity of the Cervical Spinal Cord

ObjectiveTo design and develop a high-density (HD) electrode system that describes the position of surface electrodes for recording electrophysiological signals from the human cervical spinal cord. The system is intended to standardize experimental recordings and facilitate the subsequent analysis of evoked and spontaneous spinal cord neural activity, using high-density electrospinography (HD-ESG). MethodThe proposed system (SC10-X/U) describes the locations of up to 76 channels with a unique nomenclature, where the division of the spinal cord (SC) electrode space was inspired by the EEG 10-10 system. As proof of concept, spinal evoked potentials in response to median nerve stimulation at the wrist were recorded from 10 participants and characterized based on a 64-channel derivation from the SC10-X/U system. ResultsFollowing the design criteria, the SC10-X/U defines 76 electrode positions and its configuration. HD-ESG system was utilized to successfully record evoked spinal responses and significant N13 and P9 potential were observed in response to the stimulation. The spinal N13 potential had a latency of 13.2 +-1.1ms (mean +-SD) after stimulation. A topographic map of the N13 electro-spinal activity using the 64-channel recording system revealed an epicentre at C5-C7 dorsal-vertebral locations (ML4 - ML6 electrodes). ConclusionThe proposed SC10-X/U system will facilitate standardized recording and analysis of high-density ESG signals from the human cervical spinal cord. The system defines electrode locations to promote standardization across different individuals, studies, and clinical and research centres. The HD-ESG evoked potentials recorded using the proposed system were comparable to those observed in previous non-HD studies. The presented topographic maps conform to known neurophysiological and neuroanatomical findings. This served to validate the design and development of the electrode system and patch for future studies.

neuroscience↗

bioRxiv2023

Emergence of ISAba1-linked oxacillinase genes among carbapenem resistant Acinetobacter baumannii isolates in a tertiary cardiac center, Nepal

Insertion sequence contributes to the emergence of carbapenem resistance by dissemination of carbapenemase genes and providing promoter for their overexpression. This study aims to ascertain the occurrence of ISAba1-linked OXA carbapenemase genes and its relevance to carbapenem resistance level in Acinetobacter baumannii. This hospital based descriptive study was conducted at Shahid Gangalal National Heart Center, Kathmandu, Nepal. An overall of 1,291 clinical specimens received for routine culture and antibiotic susceptibility testing throughout the study period were included in this study. Identification of Acinetobacter baumannii was validated through detection of intrinsic blaOXA-51-like gene by polymerase chain reaction (PCR). Antibiotic susceptibility was tested by Kirby-Bauer disc diffusion approach and minimum inhibitory concentration (MIC) of meropenem was assessed through agar dilution method. Uniplex PCR assays were performed to detect genes encoding oxacillinases and ISAba1. Upstream association of insertion element, ISAba1 to oxacillinase genes was assessed through PCR mapping strategy using ISAba1F and OXA-51R/OXA-23R primers. Out of the 340 bacteria isolated, only 40 (11.8%) were Acinetobacter baumannii. All isolates were resistant against meropenem with MIC value ranging from 16-256 g/ml. blaOXA-23-like genes was present in every isolate but blaOXA-58 in just two isolates (5%). All isolates had ISAba1 either above blaOXA-23-like or blaOXA-51-like gene. Higher MIC90 value of meropenem (243.20 g/ml) was found in A. baumannii cluster with ISAba1-linked upstream to both blaOXA-23-like and blaOXA-51-like genes, thus depicting their eminent role to enhanced carbapenem resistance. Acinetobacter baumannii isolates with ISAba1-linked oxacillinase genes are rapidly emerging in clinical settings of Nepal. Thus, medical communities need to be prepared and enable targeted approaches for managing burgeoning problem of carbapenem resistance.

microbiology↗

bioRxiv2019

Non-Parametric Rank Statistics for Spectral Power and Coherence

Despite advances in multivariate spectral analysis of neural signals, the statistical inference of measures such as spectral power and coherence in practical and real-life scenarios remains a challenge. The non-normal distribution of the neural signals and presence of artefactual components make it difficult to use the parametric methods for robust estimation of measures or to infer the presence of specific spectral components above the chance level. Furthermore, the bias of the coherence measures and their complex statistical distributions are impediments in robust statistical comparisons between 2 different levels of coherence. Non-parametric methods based on the median of auto-/cross-spectra have shown promise for robust estimation of spectral power and coherence estimates. However, the statistical inference based on these non-parametric estimates remain to be formulated and tested. In this report a set of methods based on non-parametric rank statistics for 1-sample and 2-sample testing of spectral power and coherence is provided. The proposed methods were demonstrated and tested using simulated neural signals in different conditions. The results show that non-parametric methods provide robustness against artefactual components. Moreover, they provide new possibilities for robust 1-sample and 2-sample testing of the complex coherency function, including both the magnitude and phase, where existing methods fall short of functionality. The utility of the methods were further demonstrated by examples on experimental neural data. The proposed approach provides a new framework for non-parametric spectral analysis of digital signals. These methods are especially suited to neuroscience and neural engineering applications, given the attractive properties such as minimal assumption on distributions, statistical robustness, and the diverse testing scenarios afforded.

bioinformatics↗

bioRxiv2019

Socioeconomic Differentials in Hypertension based on JNC7 and ACC/AHA 2017 Guidelines Mediated by Body Mass Index: Evidence from Nepal Demographic and Health Survey

BackgroundUnlike developed countries; higher socioeconomic status (SES, education, and wealth) is associated with hypertension in low and middle-income countries (LMICs) with limited evidence. We examined the associations between SES and hypertension in Nepal and the extent to which these associations vary by sex and urbanity. The body mass index (BMI) was examined as a secondary outcome and assessed as a potential mediator.\n\nMaterials and methodsWe analyzed the latest Nepal Demographic and Health Survey data (N=13,436) collected between June 2016 and January 2017, using a multistage stratified sampling technique. Participants aged 15 years or older from selected households were interviewed with an overall response rate of 97%. Main outcomes were hypertension and normal blood pressure defined by the widely used Seventh Report of the Joint National Committee (JNC 7), and the American College of Cardiology/American Heart Association (ACC/AHA) 2017.\n\nResultsThe prevalence of hypertension was higher in Nepalese men than women. The likelihood of having hypertension was more than double for individuals in the highest versus lowest wealth quintiles [men: OR 2.13, 95% CI 1.60-2.85); women: OR 2.54, 95% CI 2.00- 3.24] and for individuals with the higher education versus no education [men: OR 2.38, 95% CI 1.75-3.23; women: OR 1.63, 95% CI 1.18-2.25]. The associations between SES and hypertension were different by sex and urbanity. These associations were mediated by BMI.\n\nConclusionsHigher SES was positively associated with the higher likelihood of having hypertension in Nepal according to both JNC 7 and ACC/AHA 2017 guidelines. These associations were mediated by BMI, which may help to explain broader socioeconomic differentials in CVD and related risk factors, particularly in terms of education and wealth. Our study suggests that the mediating factor of BMI should be tackled to diminish the risk of CVD in people with higher SES in LMICs.

epidemiology↗