Multi-electrode nerve cuff recording - model analysis of the effects of finite cuff length

The effect of finite cuff length on the signals recorded by electrodes at different positions along the nerve was analysed in a model study. Relations were derived using a one-dimensional model. These were evaluated in a more realistic axially symmetric 3D model. This evaluation indicated that the cuff appeared shorter because of edge effects at the beginning and end of the cuff. The method for velocity selective filtering introduced by Donaldson was subsequently analysed. In this method, velocity selective filtering is achieved by summing the signals of subsequent tripoles after applying time shifts tuned to a certain conduction velocity. It was also found that the optimum electrode distance for a given cuff length for maximum summed RMS of symmetrical tripoles in the cuff is larger than when evaluating peak-peak amplitudes of single fibre action potentials. Velocity selective filtering yields better selectivity when using symmetrical tripoles, but may yield larger signal RMS when using the wider asymmetrical tripoles, potentially allowing for shorter cuffs. It is speculated that application of a multi-electrode reference may improve velocity selectivity for asymmetrical tripoles

Coding model of visual stimuli in the optic nerve

Electrophysiological records are a standard procedure in the study of neuronal coding in the visual system. In this paper we propose a model that can predict the electrophysiological record of electrical activity in the optic nerve evoked by visual stimuli projected on the retina. This development contemplates certain processes of coding the visual information realized in retina and how it is spread by the nerve fibers that compose the optic nerve. The results reveal that the response of the model is adequately adjusted to the experimentally obtained potentials.Fil: Soletta, Jorge Humberto. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Pizá, Alvaro Gabriel. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Lucianna, Facundo Adrián. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Albarracin, Ana Lia. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Farfan, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán; Argentin

Modeling The Electrical Activity in MyelinatedNerve Fibers: Towards the Electrophysiological Validation of Neuronal Bridges

Cuando ocurren lesiones severas en el Tejido Nervioso Central o Periférico, a menudo se desencadenan eventos que dañan permanentemente la función neurológica conduciendo así al déficit motor y sensorial del paciente. El uso de andamios de biomateriales para crear puentes que restablezcan las conexiones perdidas son prometedores, pero actualmente tienen una aplicabilidad limitada y las validaciones biológicas y electrofisiológicas demandan un tiempo considerable por lo que aún sigue siendo un campo explorado por numerosos investigadores en todo el mundo. En este trabajo proponemos un modelo empírico simplificado que describe la generación y conducción de un potencial de acción compuesto a lo largo de fibras mielínicas. La validación electrofisiológica del modelo se realizó a través del análisis cualitativo en tres situaciones experimentales en los cuales se evocan potenciales de acción compuestos: a) nervio ciático del sapo, b) axones gigantes laterales y axón gigante medial de una lombriz, y c) nervio infraorbitario en ratas. Los resultados ponen en evidencia la gran versatilidad del modelo empírico propuesto a los diferentes potenciales de acción evocados. El modelo propuesto podría convertirse en una valiosa herramienta para determinar el porcentaje de fibras funcionalmente conectadas a través de puentes neuronales fabricados con diversos materiales.When severe injuries occur in the Central or Peripheric Nervous Tissue, this often triggers events that permanently damage the neurological function, which leads to a reduction in the patient’s quality of life. The use of bio-materials scaffolding to create bridges that re-establish the lost connections are promising, but currently, have limited applicability; and electrophysiological and biological validations demand considerable time, so it is still a field being explored by many investigators around the world. In this paper a simplified empirical model is proposed to describe an action potential generation an conduction through myelinic fibers. The model's electrophysiological validation was performed through qualitative analysis in three experimental situations that call for action potential: a) sciatic nerve in frog, b) giant lateral axons and giant medial axon in earthworm, and c) infraorbital nerve in rats. Results evidence the proposed empirical model's great versatility to the different evoked action potentials. The proposed model could become a valuable tool to determine the percentage of functionally connected fibers through neural bridges made of various materials.Fil: de Marco, Nilda Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Socci, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Goy, Carla Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Albarracin, Ana Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Felice, Carmelo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Farfan, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentin

Comparative study of extracellular recording methods for analysis of afferent sensory information: Empirical modeling, data analysis and interpretation

Background: Physiological studies of sensorial systems often require the acquisition and processing of data extracted from their multiple components to evaluate how the neural information changes in relation to the environment changes. In this work, a comparative study about methodological aspects of two electrophysiological approaches is described. New method: Extracellular recordings from deep vibrissal nerves were obtained by using a customized microelectrode Utah array during passive mechanical stimulation of rat´s whiskers. These recordings were compared with those obtained with bipolar electrodes. We also propose here a simplified empirical model of the electrophysiological activity obtained from a bundle of myelinated nerve fibers. Results: The peripheral activity of the vibrissal system was characterized through the temporal and spectral features obtained with both recording methods. The empirical model not only allows the correlation between anatomical structures and functional features, but also allows to predict changes in the CAPs morphology when the arrangement and the geometry of the electrodes changes. Comparison with existing method(s): This study compares two extracellular recording methods based on analysis techniques, empirical modeling and data processing of vibrissal sensory information. Conclusions: This comparative study reveals a close relationship between the electrophysiological techniques and the processing methods necessary to extract sensory information. This relationship is the result of maximizing the extraction of information from recordings of sensory activity.Fil: Farfan, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Soto Sanchez, Cristina. Universidad de Miguel Hernández; España. Consorcio Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina; EspañaFil: Pizá, Alvaro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Albarracin, Ana Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Soletta, Jorge Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Lucianna, Facundo Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Fernandez, Esteve. Universidad de Miguel Hernández; España. Consorcio Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina; Españ

Deep brain drug-delivery control using vagus nerve communications

Vagus nerve stimulation (VNS) uses electrical impulses applied at the neck in order to mitigate the effects of, for example, epileptic seizures. We propose using VNS to provide data pulses to communicate with a drug-delivery system embedded near the brainstem. We model the generation of a vagus nerve compound action potential (CAP), calculating the signal attenuation and the resulting transmission range. The metabolic cost of CAP transmission in terms of the use of adenosine triphosphate (ATP) is also calculated. The channel capacity for on-off keying (OOK) is computed from the CAP characteristics, the neural refractory period and the level of background neural noise. The resulting low bit-rate, unidirectional asynchronous transmission system is analysed for the use of different methods of forward error correction (FEC) to improve bit-error rate (BER). We show a proposed data packet structure that could deliver instructions to an embedded drug-delivery system with multiple addressable drug reservoirs. We also analyse the scope for powering the drug-delivery system with energy harvested from cerebrospinal glucose

Signal strength versus cuff length in nerve cuff electrode recordings

Abstract—When a nerve cuff electrode is used for the recording of signals from peripheral nerves, cuff dimensions have to be chosen. Traditionally, the peak-to-peak amplitude of the single-fiber action potential (SFAP) is optimized through the choice of cuff diameter and cuff length. In this paper, the dependency of the root-mean-square (RMS) value of the nerve signal on the cuff dimensions was studied and compared with the peak-to-peak value of the SFAP. A simple approximation for signal optimization by cuff dimensioning is suggested. The results were obtained from modeled SFAPs and from the electroneurogram (ENG) created by superimposed SFAPs, obtained from an inhomogeneous volume conductor model. The results show that the RMS value of the nerve signal is consid-erably more sensitive to the cuff length than the SFAP peak-to-peak amplitude, and that the RMS of the ENG is a linear function of the fiber diameter. Index Terms—Action potential, cuff dimensions, ENG, nerve cuff electrode. I

Electromyogram Interference Reduction In Neural Signal Recording Using Simple RC Compensation Circuits

Neuroprosthesis can partially restore lost motor functionalities of individuals such as bladder voiding using functional electrical stimulation (FES) techniques. FES involves applying pattern of electrical current pulses using implanted electrodes to trigger affected nerves that are damaged due to paralysis. A neural signal recorded using tripolar cuff electrodes is significantly contaminated due to the presence of EMG interference from the surrounding muscles. Conventional neural amplifiers are unable to remove such interferences and modifications to the design are required. The modification to the design of the Quasi-tripole (QT) amplifier is considered in this work to minimise the EMG interferences from neural signal recording. The analogy between this modified version of QT known as mQT and Wheatstone bridge claims to neutralise the EMG interference by adding compensation circuit to either end of the outer electrodes of the tripolar cuff and therefore balancing the bridge. In this work, we present simple 3 and 2 stage RC compensation circuits to minimise EMG interference in trying to balance the bridge in the neural frequency band of interest (500-10kHz). It is shown that simple RC compensation circuit in series reduces EMG interference only at the spot frequency rather than linearly in the entire frequency band of interest. However, two and three stages RC ladder compensation circuits mimicking electrode-electrolyte interface, can minimize the EMG interference linearly in the entire frequency band of interest, without requiring any readjustment to their components. The aim is to minimise EMG interference as close to null as possible. Invitro testing of about 20% imbalanced cuff electrode with proposed 3 and 2 stage RC ladder compensation circuits resulted in linear EMG interference reduction atleast by a factor of 6. On an average, this yielded an improvement of above 80% EMG minimisation, in contrast to above 90% observed in the optimisation results, when 1Ω transimpedance (EMG) was introduced into the setup. Further improvements to the setup and design can give more promising results in reliable neural signal recording for FES applications

Biomimétoca Neuronal del Sistema Sensorial Periférico de las Vibrisas de la Rata

Este trabajo de tesis está basado en un importante know-how de procedimientos electrofisiológicos para el estudio del sistema vibrisal de la rata, los cuales incluyen estudios de conducción nerviosa para comprender los mecanismos fisiológicos del sistema y estudios conductuales. Estos estudios fueron dirigidos a una de las capacidades sensoriales más sobresalientes de la rata: la capacidad de discriminar objetos de diferentes texturas. Se pusieron en evidencia estrategias conductuales que permitirían a los roedores mejorar la percepción de la información táctil y la existencia de patrones temporales en los aferentes primarios relacionados a la rugosidad de las superficies palpadas.Estos hallazgos electrofisiológicos condujeron, naturalmente, a preguntas tales como: ¿qué característica física de la superficie de rozamiento está siendo codificada por el sistema vibrisal en determinadas condiciones?, ¿Cómo se trasmite esa información? y ¿todas las vibrisas transmiten de igual forma la información?Para comenzar a responder estas preguntas, fue necesario abordar el estudio de las características morfológicas relevantes de las superficies de rozamiento, desarrollar técnicas de procesamiento de la información de las señales electrofisiológicas, modelar el sistema y estudiar posibles diferencias funcionales entre las vibrisas. Así quedaron planteados los objetivos de la tesis.En el desarrollo de este trabajo de tesis se propuso una herramienta estadística, basada en la teoría de la información, que nos permitió cuantificar la información táctil presente en la actividad eléctrica de las fibras nerviosas que inervan las vibrisas; se modeló matemáticamente el comportamiento eléctrico del nervio vibrisal lo que permitió interpretar mejor el significado/motivo por el cual los potenciales evocados del registro se presentan con diferentes formas, amplitud y duración; se realizaron registros electrofisiológicos en la innervación de varias vibrisas en forma simultánea cuando estas eran estimuladas con superficies de diferente rugosidad para revelar y caracterizar los códigos neuronales involucrados en la integración sensorial. Además, se hizo un análisis de respuesta en frecuencia de varias vibrisas que demostró qué, aunque todos los senos foliculares son anatómicamente similares, funcionalmente son muy diferentes. Cada folículo está preparado para tener mayor sensibilidad para un estímulo de frecuencia específico, que a su vez está en sintonía con su vibrisa, cuya frecuencia de resonancia depende exclusivamente de sus características físicas.Por último, considerando los parámetros generales del proceso de transducción determinados en el transcurso de la tesis tales como linealidad, sensibilidad y capacidad de adaptación a diferentes modalidades del estímulo, se plantearon los criterios para una futura implementación en sistemas tecnológicos multisensoriales biomiméticos lo cual representa el mayor aporte de la tesis al conocimiento científico y tecnológico.Fil: Pizá, Alvaro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentin

Neutralisation of myoelectric interference from recorded nerve signals using models of the electrode impedance

Any form of paralysis due to spinal cord injury or other medical condition, can have a significant impact on the quality and life expectancy of an individual. Advances in medicine and surgery have offered solutions that can improve the condition of a patient, however, most of the times an individual’s life does not dramatically improve. Implanted neuroprosthetic devices can partially restore the lost functionalities by means of functional electrical stimulation techniques. This involves applying patterns of electrical current pulses to innervate the neural pathways between the brain and the affected muscles/organs, while recording of neural information from peripheral nerves can be used as feedback to improve performance. Recording naturally occurring nerve signals via implanted electrodes attached to tripolar amplifier configurations is an approach that has been successfully used for obtaining desired information in non-acute preparations since the mid-70s. The neural signal (i.e. ENG), which can be exploited as feedback to another system (e.g. a stimulator), or simply extracted for further processing, is then intrinsically more reliable in comparison to signals obtained by artificial sensors. Sadly, neural recording of this type can be greatly compromised by myoelectric (i.e. EMG) interference, which is present at the neural interface and registered by the recording amplifier. Although current amplifier configurations reduce myoelectric interference this is suboptimal and therefore there is room for improvement. The main difficulty exists in the frequency-dependence of the electrode-tissue interface impedance which is complex. The simplistic Quasi-Tripole amplifier configuration does not allow for the complete removal of interference but it is the most power efficient because it uses only one instrumentation amplifier. Conversely, the True-Tripole and its developed automatic counterpart the Adaptive-Tripole, although minimise interference and provide means of compensating for the electrode asymmetries and changes that occur to the neural interface (e.g. due to tissue growth), they do not remove interference completely as the insignificant electrode impedance is still important. Additionally, removing interference apart from being dependent on the frequency of the interfering source, it is also subject to its proximity and orientation with respect to the recording electrodes, as this affects the field. Hence neutralisation with those two configurations, in reality, is not achieved in the entire bandwidth of the neural signal in the interfering spectrum. As both are less power efficient than the Quasi-Tripole an alternative configuration offering better performance in terms of interference neutralisation (i.e. frequency-independent, insensitive to the external interference fields) and, if possible, consume less power, is considered highly attractive. The motivation of this work is based on the following fact: as there are models that can mimic the frequency response of metal electrodes it should be possible, by constructing a network of an equivalent arrangement to the impedance of electrodes, to fit the characteristic neutralisation impedance – the impedance needed to balance a recording tripole – and ideally require no adjustment for removing interference. The validity of this postulation is proven in a series of in-vitro preparations using a modified version of the Quasi-Tripole made out of discrete circuit components where an impedance is placed at either side of the outer electrodes for balancing the recording arrangement. Various models were used in place of that impedance. In particular, representing the neutralisation impedance as a parallel RC reduced interference by a factor of 10 at all frequencies in the bandwidth of the neural signal while removed it completely at a spot frequency. Conversely, modelling the effect of the constant phase angle impedance of highly polarisable electrodes using a 20 stages non-uniform RC ladder network resulted in the minimisation of interference without the initial requirement of continuous adjustment. It is demonstrated that with a model that does not perfectly fit the impedance profile of a monopolar electrochemical cell an average reduction in interference of about 100 times is achieved, with the cell arranged as a Wheatstone bridge that can be balanced in the ENG band