Imperial College London

DrKonstantinNikolic

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Senior Research Fellow
 
 
 
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Contact

 

+44 (0)20 7594 1594k.nikolic

 
 
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Location

 

Bessemer 420CBessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

99 results found

Cork SC, Eftekhar A, Mirza KB, Zuliani C, Nikolic K, Gardiner JV, Bloom SR, Toumazou Cet al., 2018, Extracellular pH monitoring for use in closed-loop vagus nerve stimulation, JOURNAL OF NEURAL ENGINEERING, Vol: 15, ISSN: 1741-2560

JOURNAL ARTICLE

Jarvis S, Nikolic K, Schultz SR, 2018, Neuronal gain modulability is determined by dendritic morphology: A computational optogenetic study, PLOS COMPUTATIONAL BIOLOGY, Vol: 14, ISSN: 1553-734X

JOURNAL ARTICLE

Markar SR, Wiggins T, Antonowicz S, Chin S-T, Romano A, Nikolic K, Evans B, Cunningham D, Mughal M, Lagergren J, Hanna GBet al., 2018, Assessment of a Noninvasive Exhaled Breath Test for the Diagnosis of Oesophagogastric Cancer., JAMA Oncol

Importance: Early esophagogastric cancer (OGC) stage presents with nonspecific symptoms. Objective: The aim of this study was to determine the accuracy of a breath test for the diagnosis of OGC in a multicenter validation study. Design, Setting, and Participants: Patient recruitment for this diagnostic validation study was conducted at 3 London hospital sites, with breath samples returned to a central laboratory for selected ion flow tube mass spectrometry (SIFT-MS) analysis. Based on a 1:1 cancer:control ratio, and maintaining a sensitivity and specificity of 80%, the sample size required was 325 patients. All patients with cancer were on a curative treatment pathway, and patients were recruited consecutively. Among the 335 patients included; 172 were in the control group and 163 had OGC. Interventions: Breath samples were collected using secure 500-mL steel breath bags and analyzed by SIFT-MS. Quality assurance measures included sampling room air, training all researchers in breath sampling, regular instrument calibration, and unambiguous volatile organic compounds (VOCs) identification by gas chromatography mass spectrometry. Main Outcomes and Measures: The risk of cancer was identified based on a previously generated 5-VOCs model and compared with histopathology-proven diagnosis. Results: Patients in the OGC group were older (median [IQR] age 68 [60-75] vs 55 [41-69] years) and had a greater proportion of men (134 [82.2%]) vs women (81 [47.4%]) compared with the control group. Of the 163 patients with OGC, 123 (69%) had tumor stage T3/4, and 106 (65%) had nodal metastasis on clinical staging. The predictive probabilities generated by this 5-VOCs diagnostic model were used to generate a receiver operator characteristic curve, with good diagnostic accuracy, area under the curve of 0.85. This translated to a sensitivity of 80% and specificity of 81% for the diagnosis of OGC. Conclusions and Relevance: This study shows the potential of breath analysis in noninvasive

JOURNAL ARTICLE

Mirza KB, Alenda A, Eftekhar A, Grossman N, Nikolic K, Bloom SR, Toumazou Cet al., 2018, Influence of Cholecystokinin-8 on Compound Nerve Action Potentials from Ventral Gastric Vagus in Rats., Int J Neural Syst, ISSN: 0129-0657

OBJECTIVE: Vagus Nerve Stimulation (VNS) has shown great promise as a potential therapy for a number of conditions, such as epilepsy, depression and for Neurometabolic Therapies, especially for treating obesity. The objective of this study was to characterize the left ventral subdiaphragmatic gastric trunk of vagus nerve (SubDiaGVN) and to analyze the influence of intravenous injection of gut hormone cholecystokinin octapeptide (CCK-8) on compound nerve action potential (CNAP) observed on the same branch, with the aim of understanding the impact of hormones on VNS and incorporating the methods and results into closed loop implant design. METHODS: The cervical region of the left vagus nerve (CerVN) of male Wistar rats was stimulated with electric current and the elicited CNAPs were recorded on the SubDiaGVN under four different conditions: Control (no injection), Saline, CCK[Formula: see text] (100[Formula: see text]pmol/kg) and CCK[Formula: see text] (1000[Formula: see text]pmol/kg) injections. RESULTS: We identified the presence of A[Formula: see text], B, C1, C2, C3 and C4 fibers with their respective velocity ranges. Intravenous administration of CCK in vivo results in selective, statistically significant reduction of CNAP components originating from A and B fibers, but with no discernible effect on the C fibers in [Formula: see text] animals. The affected CNAP components exhibit statistically significant ([Formula: see text] and [Formula: see text]) higher normalized stimulation thresholds. CONCLUSION: This approach of characterizing the vagus nerve can be used in closed loop systems to determine when to initiate VNS and also to tune the stimulation dose, which is patient-specific and changes over time.

JOURNAL ARTICLE

Troiani F, Nikolic K, Constandinou TG, 2018, Simulating optical coherence tomography for observing nerve activity: A finite difference time domain bi-dimensional model.

We present a finite difference time domain (FDTD) model for computation of A line scans in time domain optical coherence tomography (OCT). The OCT output signal is created using two different simulations for the reference and sample arms, with a successive computation of the interference signal with external software. In this paper we present the model applied to two different samples: a glass rod filled with water-sucrose solution at different concentrations and a peripheral nerve. This work aims to understand to what extent time domain OCT can be used for non-invasive, direct optical monitoring of peripheral nerve activity.

WORKING PAPER

Troiani F, Nikolic K, Constandinou TG, 2018, Simulating optical coherence tomography for observing nerve activity: a finite difference time domain bi-dimensional model, PLoS ONE, Pages: 1-14, ISSN: 1932-6203

We present a finite difference time domain (FDTD) model for computation of A line scans in time domain optical coherence tomography (OCT). The OCT output signal is created using two different simulations for the reference and sample arms, with a successive computation of the interference signal with external software. In this paper we present the model applied to two different samples: a glass rod filled with water-sucrose solution at different concentrations and a peripheral nerve. This work aims to understand to what extent time domain OCT can be used for non-invasive, direct optical monitoring of peripheral nerve activity.

JOURNAL ARTICLE

Evans BD, Nikolic K, 2017, From bytes to insights with modelling as a service a new paradigm for computational modelling illustrated with PyRhO, 12th IEEE Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 316-319, ISSN: 2163-4025

Increasingly large datasets are being made publically available yet the methods and modelling skills to analyze them are lagging behind. In an effort to overcome barriers to analyzing and modelling data we propose the paradigm of Modelling as a Service (MaaS). As a proof-of-concept, we present a case study of the MaaS paradigm with computational tools for optogenetics based upon PyRhO. We demonstrate the benefits it confers in terms of enhanced scope for collaboration, reproducibility and ease of use, especially for scientists with a limited computational background, and discuss directions for future growth. Eventually we aim to grow this project in scope to encompass other modelling and analysis tools, and migrate to JupyterHub for persistent individual user accounts and storage. In the meantime, we hope that this approach will serve to demonstrate how MaaS can substantially increase the appeal and accessibility of modelling.

CONFERENCE PAPER

Gaspar N, Sondhi A, Evans B, Nikolic Ket al., 2017, A Low-power Neuromorphic System for Retinal Implants and Sensory Substitution, 12th IEEE Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 78-81, ISSN: 2163-4025

This paper describes the design and operation of a system which can be used as a Visual to Auditory Sensory Substitution Device (SSD), as well as the front-end of a real-time retinal prosthesis (RP) or Vision Augmentation (VA) system. Such systems consist of three components: a sensory block to capture the visual scene, a processing block to manage the collected data and generate stimulus patterns, and an output block. For the sensory block we use a Dynamic Vision Sensor (DVS) instead of a conventional camera. A microcontroller is used as the processing block, which receives asynchronous inputs from the DVS in the form of ON/OFF events and treats them like post-synaptic potentials. A simple algorithm based on an Integrate & Fire neuron model is used to emulate temporal contrast sensitive Retinal Ganglion Cells (RGCs). For an RP system the output would be an implanted electrode array, whereas for the SSD a sound is activated based on a certain mapping algorithm. The results are shown in the form of ON or OFF events on the LED matrix (equivalent to the stimulation pattern on an electrode array in the case of an RP), and in the form of a stereo sound output.

CONFERENCE PAPER

Luo J, Nikolic K, Evans BD, Dong N, Sun X, Andras P, Yakovlev A, Degenaar Pet al., 2017, Optogenetics in Silicon: A Neural Processor for Predicting Optically Active Neural Networks, IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, Vol: 11, Pages: 15-27, ISSN: 1932-4545

JOURNAL ARTICLE

Troiani F, Nikolic K, Constandinou TG, 2017, Optical coherence tomography for compound action potential detection: a computational study, Conference on Optical Coherence Imaging Techniques and Imaging in Scattering Media II, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

CONFERENCE PAPER

Evans BD, Jarvis S, Schultz SR, Nikolic Ket al., 2016, PyRhO: A Multiscale Optogenetics Simulation Platform, FRONTIERS IN NEUROINFORMATICS, Vol: 10, ISSN: 1662-5196

JOURNAL ARTICLE

Nikolic K, Evans B, 2016, Identifying optimal feature transforms for classification and prediction in biological systems: recovering receptive field vectors from sparse recordings, International Conference on Machine Learning (ICML), Workshop on Computational Biology

With biological systems it is often hard to adequately sample the entire input space. With sensoryneural systems this can be a particularly acute problem, with very high dimensional natural inputs andtypically sparse spiking outputs. Here we present an information theory based approach to analysespiking data of an early sensory pathway, demonstrated on retinal ganglion cells (RGC) responding tonatural visual scene stimuli (Katz et al., 2016). We used a non-parametric technique based on theconcept of mutual information (MI), in particular, Quadratic Mutual Information (QMI). The QMIallowed us to very efficiently search the high dimensional space formed by the visual input for a muchsmaller dimensional subspace of Receptive Field Vectors (RFV). RFVs give the most informationabout the response of the cell to natural stimuli. This approach allows us to identify the RFVs far moreefficiently using limited data as we can search the complete stimulus space for multiple vectorssimultaneously. The RFVs were also used to predict the RGCs’ responses to any natural stimuli.Another suitable area of application of this algorithm is in diagnostic inference. Currently we areadapting the method to be used for identifying the cancer markers in the volatile organic compoundspresent in exhaled breath. Once the maximally informative features are established they can be usedfor diagnostic predictions on new breath samples. Preliminary results of the breathomics analysis willbe discussed at the conference.There are several other potential applications such as multiclass categorisation for bacterial strainsusing ISFET arrays for DNA sequencing. This algorithm can be part of a rapid point-of-care device foridentifying the specific infectious agents and recommending appropriate antibiotics.Here we will focus on presenting the algorithm using the example of RFVs of RGCs.

CONFERENCE PAPER

Troiani F, Nikolic K, Constandinou TG, 2016, Optical coherence tomography for detection of compound action potential in Xenopus Laevis sciatic nerve, Conference on Clinical and Translational Neurophotonics; Neural Imaging and Sensing; and Optogenetics and Optical Manipulation, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

CONFERENCE PAPER

Evans BD, Jarvis S, Schultz SR, Nikolic Ket al., 2015, PyRhO: a virtual optogenetics laboratory, BMC Neuroscience, Vol: 16, Pages: P178-P178, ISSN: 1471-2202

JOURNAL ARTICLE

Gaspar N, Sondhi A, Evans B, Nikolic Ket al., 2015, Live Demonstration: A Low-power Neuromorphic System for Retinal Implants and Sensory Substitution, 11th IEEE Annual Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 178-178, ISSN: 2163-4025

CONFERENCE PAPER

Leow HS, Nikolic K, 2015, Machine Vision Using Combined Frame-based and Event-based Vision Sensor, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 706-709, ISSN: 0271-4302

CONFERENCE PAPER

Rapeaux A, Nikolic K, Williams I, Eftekhar A, Constandinou TGet al., 2015, Fiber Size-Selective Stimulation using Action Potential Filtering for a Peripheral Nerve Interface: A Simulation Study, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 3411-3414, ISSN: 1557-170X

CONFERENCE PAPER

Wadehn F, Schieban K, Nikolic K, 2015, Motion Sensitivity Analysis of Retinal Ganglion Cells in Mouse Retina using Natural Visual Stimuli, 2015 37TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), Pages: 1658-1662, ISSN: 1557-170X

JOURNAL ARTICLE

Jarvis SJ, Nikolic K, Schultz SR, 2014, Optical coactivation in cortical cells: reprogramming the excitation-inhibition balancing act to control neuronal gain in abstract and detailed models, BMC Neuroscience, Vol: 15, Pages: F1-F1, ISSN: 1471-2202

JOURNAL ARTICLE

Luan S, Williams I, Nikolic K, Constandinou TGet al., 2014, Neuromodulation: present and emerging methods., Front Neuroeng, Vol: 7, ISSN: 1662-6443

Neuromodulation has wide ranging potential applications in replacing impaired neural function (prosthetics), as a novel form of medical treatment (therapy), and as a tool for investigating neurons and neural function (research). Voltage and current controlled electrical neural stimulation (ENS) are methods that have already been widely applied in both neuroscience and clinical practice for neuroprosthetics. However, there are numerous alternative methods of stimulating or inhibiting neurons. This paper reviews the state-of-the-art in ENS as well as alternative neuromodulation techniques-presenting the operational concepts, technical implementation and limitations-in order to inform system design choices.

JOURNAL ARTICLE

Reverter F, Prodromakis T, Liu Y, Georgiou P, Nikolic K, Constandinou Tet al., 2014, Design Considerations for a CMOS Lab-on-Chip Microheater Array to Facilitate the in vitro Thermal Stimulation of Neurons, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 630-633, ISSN: 0271-4302

CONFERENCE PAPER

Grossman N, Simiaki V, Martinet C, Toumazou C, Schultz SR, Nikolic Ket al., 2013, The spatial pattern of light determines the kinetics and modulates backpropagation of optogenetic action potentials, JOURNAL OF COMPUTATIONAL NEUROSCIENCE, Vol: 34, Pages: 477-488, ISSN: 0929-5313

JOURNAL ARTICLE

Jarvis S, Nikolic K, Grossman N, Schultz SRet al., 2013, Controlling the neuronal balancing act: optical coactivation of excitation and inhibition in neuronal subdomains., Pages: P348-P348, ISSN: 1471-2202

CONFERENCE PAPER

Nikolic K, Jarvis S, Grossman N, Schultz Set al., 2013, Computational Models of Optogenetic Tools for Controlling Neural Circuits with Light, 35th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 5934-5937, ISSN: 1557-170X

CONFERENCE PAPER

Nikolic K, Loizu J, 2013, Drosophila Photo-transduction Simulator, Journal of Open Research Software, Vol: 1, ISSN: 2049-9647

JOURNAL ARTICLE

Katz ML, Lutterbeck C, Nikolic K, 2012, An Implementation of Magnocellular Pathways in Event-Based Retinomorphic Systems, IEEE Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 17-20, ISSN: 2163-4025

CONFERENCE PAPER

Katz ML, Nikolic K, Delbruck T, 2012, Behavioural Emulation of Event-Based Vision Sensors, IEEE International Symposium on Circuits and Systems, Publisher: IEEE, Pages: 737-740, ISSN: 0271-4302

CONFERENCE PAPER

Katz ML, Nikolic K, Delbruck T, 2012, Live Demonstration: Behavioural Emulation of Event-Based Vision Sensorsh, IEEE International Symposium on Circuits and Systems, Publisher: IEEE, Pages: 736-736, ISSN: 0271-4302

CONFERENCE PAPER

Mou Z, Triantis IF, Woods VM, Toumazou C, Nikolic Ket al., 2012, A Simulation Study of the Combined Thermoelectric Extracellular Stimulation of the Sciatic Nerve of the Xenopus Laevis: The Localized Transient Heat Block, IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Vol: 59, Pages: 1758-1769, ISSN: 0018-9294

JOURNAL ARTICLE

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