David Guiraud - Academia.edu (original) (raw)

Papers by David Guiraud

River Publishers eBooks, Sep 1, 2022

River Publishers eBooks, Dec 1, 2019

Sensors, 2020

Patients with central respiratory paralysis can benefit from diaphragm pacing to restore respirat... more Patients with central respiratory paralysis can benefit from diaphragm pacing to restore respiratory function. However, it would be important to develop a continuous respiratory monitoring method to alert on apnea occurrence, in order to improve the efficiency and safety of the pacing system. In this study, we present a preliminary validation of an acoustic apnea detection method on healthy subjects data. Thirteen healthy participants performed one session of two 2-min recordings, including a voluntary respiratory pause. The recordings were post-processed by combining temporal and frequency detection domains, and a new method was proposed—Phonocardiogram-Derived Respiration (PDR). The detection results were compared to synchronized pneumotachograph, electrocardiogram (ECG), and abdominal strap (plethysmograph) signals. The proposed method reached an apnea detection rate of 92.3%, with 99.36% specificity, 85.27% sensitivity, and 91.49% accuracy. PDR method showed a good correlation o...

Sensors, 2022

Working towards the development of robust motion recognition systems for assistive technology con... more Working towards the development of robust motion recognition systems for assistive technology control, the widespread approach has been to use a plethora of, often times, multi-modal sensors. In this paper, we develop single-sensor motion recognition systems. Utilising the peripheral nature of surface electromyography (sEMG) data acquisition, we optimise the information extracted from sEMG sensors. This allows the reduction in sEMG sensors or provision of contingencies in a system with redundancies. In particular, we process the sEMG readings captured at the trapezius descendens and platysma muscles. We demonstrate that sEMG readings captured at one muscle contain distinct information on movements or contractions of other agonists. We used the trapezius and platysma muscle sEMG data captured in able-bodied participants and participants with tetraplegia to classify shoulder movements and platysma contractions using white-box supervised learning algorithms. Using the trapezius sensor,...

2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2018

Direct electrical stimulation (DES) at 60 Hz is used clinically to perform real-time functional m... more Direct electrical stimulation (DES) at 60 Hz is used clinically to perform real-time functional mapping of the brain and guide tumor resection during wide-awake neurosurgery. The electrophysiological effects of DES remain by far unknown, both locally and remotely. In this study, by lowering the DES frequency to 9 Hz and by using differential recording of electro-corticographic signals to improve the focality, we were able to observe that the amplitude of the initial P0 component of the direct cortical response increased when the inter-electrode distance was increased and the pulse width was decreased. This result strongly suggests that larger neural elements, including somas and axons of pyramidal neurons buried in deeper layers of the cortical column, are activated. Their activation produce the observed P0 component, which results from the synchronized summation of action potentials triggered by DES. Interestingly, the early P0 component was not observed during the usual 60 Hz DES. The study of the P0 component and subsequent evoked potentials may help decipher the effects of DES on the stimulated cortical column and identify the activation of underlying white matter fibers. This is crucial to better understand the electrophysiological diffusion of DES, especially at higher frequencies (e.g. 60 Hz).

Converging Clinical and Engineering Research on Neurorehabilitation II, 2016

A wearable, 56-channel stimulator was developed and successfully tested to drive multichannel int... more A wearable, 56-channel stimulator was developed and successfully tested to drive multichannel intrafascicular electrodes. It is able to safely elicit sensory afferent signals through the activation of 4 Time-4H intrafascicular electrodes. The STIMEP embeds not only the pulse generator but also a software that ensures: i) real time control by a hand-prosthesis, ii) embedded procedures for sensation mapping interfaced with a PC software, iii) impedance follow-up, iv) real-time safety management.

2007 14th IEEE International Conference on Electronics, Circuits and Systems, 2007

In order to extract and separate Action Potential (AP) signals according to their nerve fascicule... more In order to extract and separate Action Potential (AP) signals according to their nerve fascicule origins, we propose a new architecture of a multipolar cuff electrode and an optimized integrated acquisition circuit. The proposed electrode has a specific layout of a large number of poles in order to both reject parasitic signals, such as electromyogram and provide a maximum of spatial selectivity for ENG signals. For one channel to be recorded, we need to consider seven recording sites. A low-noise integrated circuit (ASIC) has been designed in order to perform this first step of analog processing on each set of seven considered poles

Impedance evaluation of implanted electrodes is necessary to ensure that the implant can deliver ... more Impedance evaluation of implanted electrodes is necessary to ensure that the implant can deliver the specified current, and to survey any failure due to the electrodes. To perform the identification in the implanted hardware, a simple, but sufficiently descriptive model, must be used because of the poor excitation input signal and in order to avoid complex identification algorithms. Data recorded on the first implanted SUAW patient give information on the real impedance of both neural and epimysial electrodes and an opportunity to validate simple first order models.

Toxins, 2021

Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and i... more Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and is widely used for neuromuscular disorders (involuntary spasms, dystonic disorders and spasticity). However, its therapeutic effects are usually measured by clinical scales of questionable validity. Single-fiber electromyography (SFEMG) is a sensitive, validated diagnostic technique for NMJ impairment such as myasthenia. The jitter parameter (µs) represents the variability of interpotential intervals of two muscle fibers from the same motor unit. This narrative review reports SFEMG use in BoNT-A treatment. Twenty-four articles were selected from 175 eligible articles searched in Medline/Pubmed and Cochrane Library from their creation until May 2020. The results showed that jitter is sensitive to early NMJ modifications following BoNT-A injection, with an increase in the early days’ post-injection and a peak between Day 15 and 30, when symptoms diminish or disappear. The reappearance of sy...

Sensors, 2021

Peripheral Nerve Stimulation (PNS) is a promising approach in functional restoration following ne... more Peripheral Nerve Stimulation (PNS) is a promising approach in functional restoration following neural impairments. Although it proves to be advantageous in the number of implantation sites provided compared with intramuscular or epimysial stimulation and the fact that it does not require daily placement, as is the case with surface electrodes, the further advancement of PNS paradigms is hampered by the limitation of spatial selectivity due to the current spread and variations of nerve physiology. New electrode designs such as the Transverse Intrafascicular Multichannel Electrode (TIME) were proposed to resolve this issue, but their use was limited by a lack of innovative multichannel stimulation devices. In this study, we introduce a new portable multichannel stimulator—called STIMEP—and implement different stimulation protocols in rats to test its versatility and unveil the potential of its combined use with TIME electrodes in rehabilitation protocols. We developed and tested vario...

Journal of Neural Engineering, 2019

Objective: The goal of this study was to evaluate the long-term behavior of the surface electrode... more Objective: The goal of this study was to evaluate the long-term behavior of the surface electrode through electrochemical characterization and follow up of implanted parylene/platinum microelectrodes. Approach: To this aim, we designed and manufactured specific planar electrodes for cortical implantation for a rat model. This work was included in the INTENSE® project, one of the goals of which was to prove the feasibility of selective neural recording or stimulation with cuff electrodes around the vagus nerve. Main results: After a 12-week implantation on a rat model, we can report that these microelectrodes have withstood in-vivo use. Regarding the biocompatibility of the electrodes (materials and manufacturing process), no adverse effect was reported. Indeed, after the three months implantation, we characterized limited tissue reaction beneath the electrodes and showed an increase and a stabilization of their impedance. Interestingly, the follow up of the electrochemical impedance combined with electrical stimulation highlighted a drop of the impedance up to 60% @1kHz after ten minutes of electrical stimulation at 110Hz.

PLOS ONE, 2019

Neural multicontact cuff electrodes have the potential to activate selectively different groups o... more Neural multicontact cuff electrodes have the potential to activate selectively different groups of muscles and offer more possibilities of electrical configurations compared to whole ring cuffs. Several previous studies explored multicontact electrodes with a limited set of configurations which were sorted using a selectivity index only. The objective of the present study is to classify a larger number of configurations, i.e. the way the current is spread over the 12 contacts of the cuff electrode, using additional criteria such as robustness (i.e. ability to maintain selectivity within a range of current amplitudes) and efficiency (i.e. electrical consumption of the considered multipolar configuration versus the electrical consumption of the reference whole-ring configuration). Experiments were performed on the sciatic nerve of 4 rabbits. Results indicated that the optimal configuration depends on the weights applied to selectivity, robustness and efficiency criteria. Tripolar transverse is the most robust configuration and the less efficient, whereas tripolar longitudinal ring is efficient but not robust. New configurations issued from a previous theoretical study we carried out such as steering current ring appears as good compromise between the 3 criteria.

ABSTRACTMicro-fabricated neural interfaces based on polyimide (PI) are achieving increasing impor... more ABSTRACTMicro-fabricated neural interfaces based on polyimide (PI) are achieving increasing importance in translational research. The ability to produce well-defined micro-structures with properties that include chemical inertness, mechanical flexibility and low water uptake are key advantages for these devices. This paper reports the development of the transverse intrafascicular multichannel electrode (TIME) used to deliver intraneural sensory feedback to an upper-limb amputee in combination with a sensorized hand prosthesis. A first-in-human study limited to 30 days was performed. About 90 % of the stimulation contact sites of the TIMEs maintained electrical functionality and stability during the full implant period. However, optical analysis post-explantation revealed that 62.5 % of the stimulation contacts showed signs of mechanical damage at the metallization-PI interface. Such damage likely occurred due to handling during explantation and subsequent analysis, since a significa...

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, Aug 1, 2016

In the context of functional electrical stimulation of peripheral nerves, the control of a specif... more In the context of functional electrical stimulation of peripheral nerves, the control of a specific motor or sensory functions may need selective stimulation to target the desired effect without others. In implanted stimulation, spatial selectivity is obtained using multipolar CUFF electrodes with specific spread of the current over each contact. Furthermore, electrical stimulation recruits large fibers before small ones, whereas the targeted function could be elicited by a specific fiber type i.e. fiber diameter. In our work, numerical simulations were used to investigate the combination of multipolar configuration and prepulses, in order to obtain spatially reverse recruitment order. Multipolar stimulation provides efficient spatial selectivity, whereas sub-threshold prepulses were used to reverse recruitment order with a reasonable increase of the injected charges. We compared several selective configurations combined with prepulses to show that some are able to guarantee both th...

Journal of neurology, neurosurgery, and psychiatry, Jan 12, 2018

Biosystems & Biorobotics, 2016

Transversal intrafascicular multichannel electrodes (TIME) have been developed to interface with ... more Transversal intrafascicular multichannel electrodes (TIME) have been developed to interface with peripheral nerves after upper limb amputation. Intended use is the electrical stimulation of the median and ulnar nerve to deliver sensory feedback during phantom limb pain treatment and artificial hand control. Miniaturized electrode arrays were developed on polyimide substrates with thin film metallization using sputtered iridium oxide as electrode coating. Here, we report on the essential requirements including biocompatibility, mechanical and stimulation stability that have been investigated before permission was granted by the legal authorities to conduct subchronic first-in-man clinical trials. Explants have been investigated to identify possible first failure points and optimize the devices for chronic implantation.

European Journal of Translational Myology, 2016

In functional electrical stimulation, selective stimulation of axons is desirable to activate a s... more In functional electrical stimulation, selective stimulation of axons is desirable to activate a specific target, in particular muscular function. This implies to simulate a fascicule without activating neighboring ones i.e. to be spatially selective. Spatial selectivity is achieved by the use of multicontact cuff electrodes over which the stimulation current is distributed. Because of the large number of parameters involved, numerical simulations provide a way to find and optimize electrode configuration. The present work offers a computation effective scheme and associated tool chain capable of simulating electrode-nerve interface and find the best spread of current to achieve spatial selectivity.

European Journal of Translational Myology, 2016

Spinal cord injuries (SCI) result in the loss of movement and sensory feedback as well as organs ... more Spinal cord injuries (SCI) result in the loss of movement and sensory feedback as well as organs dysfunctions. For example, nearly all SCI subjects loose their bladder control and are prone to kidney failure if they do not proceed to intermittent (self-) catheterization. Electrical stimulation of the sacral spinal roots with an implantable neuroprosthesis is a promising approach, with commercialized products, to restore continence and control micturition. However, many persons do not ask for this intervention since a surgical deafferentation is needed and the loss of sensory functions and reflexes become serious side effects of this procedure. Recent results renewed interest in spinal cord stimulation. Stimulation of existing pre-cabled neural networks involved in physiological processes regulation is suspected to enable synergic recruitment of spinal fibers. The development of direct spinal stimulation strategies aiming at bladder and bowel functions restoration would therefore app...

Journal of Neural Engineering, 2016

Neural signals along the vagus nerve (VN) drive many somatic and autonomic functions. The clinica... more Neural signals along the vagus nerve (VN) drive many somatic and autonomic functions. The clinical interest of VN stimulation (VNS) is thus potentially huge and has already been demonstrated in epilepsy. However, side effects are often elicited, in addition to the targeted neuromodulation. This review examines the state of the art of VNS applied to two emerging modulations of autonomic function: heart failure and obesity, especially morbid obesity. We report that VNS may benefit from improved stimulation delivery using very advanced technologies. However, most of the results from fundamental animal studies still need to be demonstrated in humans.

2015 IEEE Computer Society Annual Symposium on VLSI, 2015

This paper presents an original method to emulate a single fiber action potential in a quasi-infi... more This paper presents an original method to emulate a single fiber action potential in a quasi-infinite conductive volume, suitable for reproducible testing of bio-potential recording systems. The model is accurate for reproducing the biopotential even for a small electrode to fiber radial distances. Established current activities of axon is used and programmed in the developed FPGA-based instrument, the model takes into consideration action potential propagation properties, electrode to fiber radial distances, medium conductivity. This paper investigates differences in the action potential amplitude for two longitudinal probe positions one in front of a node of Ranvier (NOR) and one between two NOR, for a large range of radial distances. Results are reported and compared with simulation with a correlation level of 97.6 %. The model is realistic enough to help the design of new recording systems.

River Publishers eBooks, Sep 1, 2022

River Publishers eBooks, Dec 1, 2019

Sensors, 2020

Patients with central respiratory paralysis can benefit from diaphragm pacing to restore respirat... more Patients with central respiratory paralysis can benefit from diaphragm pacing to restore respiratory function. However, it would be important to develop a continuous respiratory monitoring method to alert on apnea occurrence, in order to improve the efficiency and safety of the pacing system. In this study, we present a preliminary validation of an acoustic apnea detection method on healthy subjects data. Thirteen healthy participants performed one session of two 2-min recordings, including a voluntary respiratory pause. The recordings were post-processed by combining temporal and frequency detection domains, and a new method was proposed—Phonocardiogram-Derived Respiration (PDR). The detection results were compared to synchronized pneumotachograph, electrocardiogram (ECG), and abdominal strap (plethysmograph) signals. The proposed method reached an apnea detection rate of 92.3%, with 99.36% specificity, 85.27% sensitivity, and 91.49% accuracy. PDR method showed a good correlation o...

Sensors, 2022

Working towards the development of robust motion recognition systems for assistive technology con... more Working towards the development of robust motion recognition systems for assistive technology control, the widespread approach has been to use a plethora of, often times, multi-modal sensors. In this paper, we develop single-sensor motion recognition systems. Utilising the peripheral nature of surface electromyography (sEMG) data acquisition, we optimise the information extracted from sEMG sensors. This allows the reduction in sEMG sensors or provision of contingencies in a system with redundancies. In particular, we process the sEMG readings captured at the trapezius descendens and platysma muscles. We demonstrate that sEMG readings captured at one muscle contain distinct information on movements or contractions of other agonists. We used the trapezius and platysma muscle sEMG data captured in able-bodied participants and participants with tetraplegia to classify shoulder movements and platysma contractions using white-box supervised learning algorithms. Using the trapezius sensor,...

2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2018

Direct electrical stimulation (DES) at 60 Hz is used clinically to perform real-time functional m... more Direct electrical stimulation (DES) at 60 Hz is used clinically to perform real-time functional mapping of the brain and guide tumor resection during wide-awake neurosurgery. The electrophysiological effects of DES remain by far unknown, both locally and remotely. In this study, by lowering the DES frequency to 9 Hz and by using differential recording of electro-corticographic signals to improve the focality, we were able to observe that the amplitude of the initial P0 component of the direct cortical response increased when the inter-electrode distance was increased and the pulse width was decreased. This result strongly suggests that larger neural elements, including somas and axons of pyramidal neurons buried in deeper layers of the cortical column, are activated. Their activation produce the observed P0 component, which results from the synchronized summation of action potentials triggered by DES. Interestingly, the early P0 component was not observed during the usual 60 Hz DES. The study of the P0 component and subsequent evoked potentials may help decipher the effects of DES on the stimulated cortical column and identify the activation of underlying white matter fibers. This is crucial to better understand the electrophysiological diffusion of DES, especially at higher frequencies (e.g. 60 Hz).

Converging Clinical and Engineering Research on Neurorehabilitation II, 2016

A wearable, 56-channel stimulator was developed and successfully tested to drive multichannel int... more A wearable, 56-channel stimulator was developed and successfully tested to drive multichannel intrafascicular electrodes. It is able to safely elicit sensory afferent signals through the activation of 4 Time-4H intrafascicular electrodes. The STIMEP embeds not only the pulse generator but also a software that ensures: i) real time control by a hand-prosthesis, ii) embedded procedures for sensation mapping interfaced with a PC software, iii) impedance follow-up, iv) real-time safety management.

2007 14th IEEE International Conference on Electronics, Circuits and Systems, 2007

In order to extract and separate Action Potential (AP) signals according to their nerve fascicule... more In order to extract and separate Action Potential (AP) signals according to their nerve fascicule origins, we propose a new architecture of a multipolar cuff electrode and an optimized integrated acquisition circuit. The proposed electrode has a specific layout of a large number of poles in order to both reject parasitic signals, such as electromyogram and provide a maximum of spatial selectivity for ENG signals. For one channel to be recorded, we need to consider seven recording sites. A low-noise integrated circuit (ASIC) has been designed in order to perform this first step of analog processing on each set of seven considered poles

Impedance evaluation of implanted electrodes is necessary to ensure that the implant can deliver ... more Impedance evaluation of implanted electrodes is necessary to ensure that the implant can deliver the specified current, and to survey any failure due to the electrodes. To perform the identification in the implanted hardware, a simple, but sufficiently descriptive model, must be used because of the poor excitation input signal and in order to avoid complex identification algorithms. Data recorded on the first implanted SUAW patient give information on the real impedance of both neural and epimysial electrodes and an opportunity to validate simple first order models.

Toxins, 2021

Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and i... more Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and is widely used for neuromuscular disorders (involuntary spasms, dystonic disorders and spasticity). However, its therapeutic effects are usually measured by clinical scales of questionable validity. Single-fiber electromyography (SFEMG) is a sensitive, validated diagnostic technique for NMJ impairment such as myasthenia. The jitter parameter (µs) represents the variability of interpotential intervals of two muscle fibers from the same motor unit. This narrative review reports SFEMG use in BoNT-A treatment. Twenty-four articles were selected from 175 eligible articles searched in Medline/Pubmed and Cochrane Library from their creation until May 2020. The results showed that jitter is sensitive to early NMJ modifications following BoNT-A injection, with an increase in the early days’ post-injection and a peak between Day 15 and 30, when symptoms diminish or disappear. The reappearance of sy...

Sensors, 2021

Peripheral Nerve Stimulation (PNS) is a promising approach in functional restoration following ne... more Peripheral Nerve Stimulation (PNS) is a promising approach in functional restoration following neural impairments. Although it proves to be advantageous in the number of implantation sites provided compared with intramuscular or epimysial stimulation and the fact that it does not require daily placement, as is the case with surface electrodes, the further advancement of PNS paradigms is hampered by the limitation of spatial selectivity due to the current spread and variations of nerve physiology. New electrode designs such as the Transverse Intrafascicular Multichannel Electrode (TIME) were proposed to resolve this issue, but their use was limited by a lack of innovative multichannel stimulation devices. In this study, we introduce a new portable multichannel stimulator—called STIMEP—and implement different stimulation protocols in rats to test its versatility and unveil the potential of its combined use with TIME electrodes in rehabilitation protocols. We developed and tested vario...

Journal of Neural Engineering, 2019

Objective: The goal of this study was to evaluate the long-term behavior of the surface electrode... more Objective: The goal of this study was to evaluate the long-term behavior of the surface electrode through electrochemical characterization and follow up of implanted parylene/platinum microelectrodes. Approach: To this aim, we designed and manufactured specific planar electrodes for cortical implantation for a rat model. This work was included in the INTENSE® project, one of the goals of which was to prove the feasibility of selective neural recording or stimulation with cuff electrodes around the vagus nerve. Main results: After a 12-week implantation on a rat model, we can report that these microelectrodes have withstood in-vivo use. Regarding the biocompatibility of the electrodes (materials and manufacturing process), no adverse effect was reported. Indeed, after the three months implantation, we characterized limited tissue reaction beneath the electrodes and showed an increase and a stabilization of their impedance. Interestingly, the follow up of the electrochemical impedance combined with electrical stimulation highlighted a drop of the impedance up to 60% @1kHz after ten minutes of electrical stimulation at 110Hz.

PLOS ONE, 2019

Neural multicontact cuff electrodes have the potential to activate selectively different groups o... more Neural multicontact cuff electrodes have the potential to activate selectively different groups of muscles and offer more possibilities of electrical configurations compared to whole ring cuffs. Several previous studies explored multicontact electrodes with a limited set of configurations which were sorted using a selectivity index only. The objective of the present study is to classify a larger number of configurations, i.e. the way the current is spread over the 12 contacts of the cuff electrode, using additional criteria such as robustness (i.e. ability to maintain selectivity within a range of current amplitudes) and efficiency (i.e. electrical consumption of the considered multipolar configuration versus the electrical consumption of the reference whole-ring configuration). Experiments were performed on the sciatic nerve of 4 rabbits. Results indicated that the optimal configuration depends on the weights applied to selectivity, robustness and efficiency criteria. Tripolar transverse is the most robust configuration and the less efficient, whereas tripolar longitudinal ring is efficient but not robust. New configurations issued from a previous theoretical study we carried out such as steering current ring appears as good compromise between the 3 criteria.

ABSTRACTMicro-fabricated neural interfaces based on polyimide (PI) are achieving increasing impor... more ABSTRACTMicro-fabricated neural interfaces based on polyimide (PI) are achieving increasing importance in translational research. The ability to produce well-defined micro-structures with properties that include chemical inertness, mechanical flexibility and low water uptake are key advantages for these devices. This paper reports the development of the transverse intrafascicular multichannel electrode (TIME) used to deliver intraneural sensory feedback to an upper-limb amputee in combination with a sensorized hand prosthesis. A first-in-human study limited to 30 days was performed. About 90 % of the stimulation contact sites of the TIMEs maintained electrical functionality and stability during the full implant period. However, optical analysis post-explantation revealed that 62.5 % of the stimulation contacts showed signs of mechanical damage at the metallization-PI interface. Such damage likely occurred due to handling during explantation and subsequent analysis, since a significa...

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, Aug 1, 2016

In the context of functional electrical stimulation of peripheral nerves, the control of a specif... more In the context of functional electrical stimulation of peripheral nerves, the control of a specific motor or sensory functions may need selective stimulation to target the desired effect without others. In implanted stimulation, spatial selectivity is obtained using multipolar CUFF electrodes with specific spread of the current over each contact. Furthermore, electrical stimulation recruits large fibers before small ones, whereas the targeted function could be elicited by a specific fiber type i.e. fiber diameter. In our work, numerical simulations were used to investigate the combination of multipolar configuration and prepulses, in order to obtain spatially reverse recruitment order. Multipolar stimulation provides efficient spatial selectivity, whereas sub-threshold prepulses were used to reverse recruitment order with a reasonable increase of the injected charges. We compared several selective configurations combined with prepulses to show that some are able to guarantee both th...

Journal of neurology, neurosurgery, and psychiatry, Jan 12, 2018

Biosystems & Biorobotics, 2016

Transversal intrafascicular multichannel electrodes (TIME) have been developed to interface with ... more Transversal intrafascicular multichannel electrodes (TIME) have been developed to interface with peripheral nerves after upper limb amputation. Intended use is the electrical stimulation of the median and ulnar nerve to deliver sensory feedback during phantom limb pain treatment and artificial hand control. Miniaturized electrode arrays were developed on polyimide substrates with thin film metallization using sputtered iridium oxide as electrode coating. Here, we report on the essential requirements including biocompatibility, mechanical and stimulation stability that have been investigated before permission was granted by the legal authorities to conduct subchronic first-in-man clinical trials. Explants have been investigated to identify possible first failure points and optimize the devices for chronic implantation.

European Journal of Translational Myology, 2016

In functional electrical stimulation, selective stimulation of axons is desirable to activate a s... more In functional electrical stimulation, selective stimulation of axons is desirable to activate a specific target, in particular muscular function. This implies to simulate a fascicule without activating neighboring ones i.e. to be spatially selective. Spatial selectivity is achieved by the use of multicontact cuff electrodes over which the stimulation current is distributed. Because of the large number of parameters involved, numerical simulations provide a way to find and optimize electrode configuration. The present work offers a computation effective scheme and associated tool chain capable of simulating electrode-nerve interface and find the best spread of current to achieve spatial selectivity.

European Journal of Translational Myology, 2016

Spinal cord injuries (SCI) result in the loss of movement and sensory feedback as well as organs ... more Spinal cord injuries (SCI) result in the loss of movement and sensory feedback as well as organs dysfunctions. For example, nearly all SCI subjects loose their bladder control and are prone to kidney failure if they do not proceed to intermittent (self-) catheterization. Electrical stimulation of the sacral spinal roots with an implantable neuroprosthesis is a promising approach, with commercialized products, to restore continence and control micturition. However, many persons do not ask for this intervention since a surgical deafferentation is needed and the loss of sensory functions and reflexes become serious side effects of this procedure. Recent results renewed interest in spinal cord stimulation. Stimulation of existing pre-cabled neural networks involved in physiological processes regulation is suspected to enable synergic recruitment of spinal fibers. The development of direct spinal stimulation strategies aiming at bladder and bowel functions restoration would therefore app...

Journal of Neural Engineering, 2016

Neural signals along the vagus nerve (VN) drive many somatic and autonomic functions. The clinica... more Neural signals along the vagus nerve (VN) drive many somatic and autonomic functions. The clinical interest of VN stimulation (VNS) is thus potentially huge and has already been demonstrated in epilepsy. However, side effects are often elicited, in addition to the targeted neuromodulation. This review examines the state of the art of VNS applied to two emerging modulations of autonomic function: heart failure and obesity, especially morbid obesity. We report that VNS may benefit from improved stimulation delivery using very advanced technologies. However, most of the results from fundamental animal studies still need to be demonstrated in humans.

2015 IEEE Computer Society Annual Symposium on VLSI, 2015

This paper presents an original method to emulate a single fiber action potential in a quasi-infi... more This paper presents an original method to emulate a single fiber action potential in a quasi-infinite conductive volume, suitable for reproducible testing of bio-potential recording systems. The model is accurate for reproducing the biopotential even for a small electrode to fiber radial distances. Established current activities of axon is used and programmed in the developed FPGA-based instrument, the model takes into consideration action potential propagation properties, electrode to fiber radial distances, medium conductivity. This paper investigates differences in the action potential amplitude for two longitudinal probe positions one in front of a node of Ranvier (NOR) and one between two NOR, for a large range of radial distances. Results are reported and compared with simulation with a correlation level of 97.6 %. The model is realistic enough to help the design of new recording systems.