Biology subjects

Raspopovic, S.

Publications and source records attributed to Raspopovic, S..

6 recordsLinked to original sources

bioRxiv2023

Biomimetic computer-to-brain communication restoring naturalistic touch sensations via peripheral nerve stimulation

Artificial communication with the brain through peripheral nerve stimulation recently showed promising results in people with sensorimotor deficits. However, these efforts fall short in delivering close-to-natural rich sensory experience, resulting in the necessity to propose novel venues for converting sensory information into neural stimulation patterns, which would possibly enable intuitive and natural sensations. To this aim, we designed and tested a biomimetic neurostimulation framework inspired by nature, able "to write" physiologically plausible information back into the residual healthy nervous system. Starting from the in-silico model of mechanoreceptors, we designed biomimetic policies of stimulation, emulating the activity of different afferent units. Then, we experimentally assessed these novel paradigms, alongside mechanical touch and commonly used, linear neuromodulations. We explored the somatosensory neuroaxis by stimulating the nerve while recording the neural responses at the dorsal root ganglion and spinal cord of decerebrated cats. Biomimetic stimulation resulted in a neural activity that travels consistently along the neuroaxis, producing the spatio-temporal neural dynamic more like the naturally evoked one. Finally, we then implemented these paradigms within the bionic device and tested it with patients. Biomimetic neurostimulations resulted in higher mobility and decreased mental effort compared to traditional approaches. The results of this neuroscience-driven technology inspired by the human body could be a model for the development of novel assistive neurotechnologies.

neuroscience↗

bioRxiv2021

Disruption Of Proprioceptive Information During Electrical Stimulation Of The Cutaneous Afferents

While neurostimulation technologies are rapidly approaching clinical applications for sensorimotor disorders, the impact of electrical stimulation on network dynamics is still unknown. Given the high degree of shared processing in neural structures, it is critical to understand if neurostimulation affects functions that are related to, but not targeted by the intervention. Here we approached this question by studying the effects of electrical stimulation of cutaneous afferents on unrelated processing of proprioceptive inputs. We recorded intra-spinal neural activity in four monkeys while generating proprioceptive inputs from the radial nerve. We then applied continuous stimulation to the radial nerve cutaneous branch and quantified the impact of the stimulation on spinal processing of proprioceptive inputs via neural population dynamics. Proprioceptive pulses consistently produced neural trajectories that were disrupted by concurrent cutaneous stimulation. This disruption propagated to the somatosensory cortex, suggesting that electrical stimulation can perturb natural information processing across the neural axis.

neuroscience↗

bioRxiv2020

A psychometric platform to collect somatosensory sensations for neuroprosthetic use

Somatosensory neuroprostheses exploit invasive and non-invasive feedback technologies to restore sensorimotor functions lost to disease or trauma. These devices use electrical stimulation to communicate sensory information to the brain. A sensation characterization procedure is thus necessary to determine the appropriate stimulation parameters and to establish a clear personalized map of the sensations that can be restored. Several questionnaires have been described in the literature to collect the quality, type, location and intensity of the evoked sensations, but there is still no standard psychometric platform. Here we propose a new psychometric system containing previously validated questionnaires on evoked sensations, which can be applied to any kind of somatosensory neuroprosthesis. The platform collects stimulation parameters used to elicit sensations; records subjects percepts in terms of sensation location, type, quality, perceptual threshold, and intensity. It further collects data using standardized assessment questionnaires and scales, performs measurements over time, and collects phantom limb pain syndrome data. The psychometric platform is user-friendly and provides clinicians with all the information needed to assess the sensory feedback. The psychometric platform was validated with three trans-radial amputees. They platform was used to assess intraneural sensory feedback provided through implanted peripheral nerve interfaces. The proposed platform could act as a new standardized assessment toolbox to homogenize the reporting of results obtained with different technologies in the field of somatosensory neuroprosthetics.

neuroscience↗

bioRxiv2019

On the Reliability of Chronically Implanted Thin-Film Electrodes in Human Arm Nerves for Neuroprosthetic Applications

Direct stimulation of peripheral nerves can successfully provide sensory feedback to amputees while using hand prostheses. Recent clinical studies have addressed this important limitation of current prostheses solutions using different implantable electrode concepts. Longevity of the electrodes is key to success. We have improved the long-term stability of the polyimide-based transverse intrafascicular multichannel electrode (TIME) that showed promising performance in clinical trials by integration of silicon carbide adhesion layers. The TIMEs were implanted in the median and ulnar nerves of three trans-radial amputees for up to six months. Here, we present the characterization of the electrical properties of the thin-film metallization as well as material status post explantationem for the first time. The TIMEs showed reliable performance in terms of eliciting sensation and stayed within the electrochemical safe limits maintaining a good working range with respect to amplitude modulation. After termination of the trials and explantation of the probes, no signs of corrosion or morphological change to the thin-film metallization was observed by means of electrochemical and optical analysis. Damage to the metallization was assigned exclusively to mechanical impacts during explantation and handling. The results indicate that thin-film metallization on polymer substrates is applicable in permanent implant system.

bioengineering↗

bioRxiv2019

Stability of Thin-Film Metallization in Flexible Stimulation Electrodes: Analysis and Improvement of in vivo Performance

Micro-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 significant change in impedance was not observed in vivo. Nevertheless, whereas device integrity is mandatory for long-term functionality in chronic implantation, measures to increase the bonding strength of the metallization-PI interface deserve further investigation. We report here that silicon carbide (SiC) is an effective adhesion-promoting layer resisting heavy electrical stimulation conditions in vivo. Optical analysis of the new electrodes revealed that the metallization remained unaltered after delivering over 14 million pulses in vivo without signs of delamination at the metallization-PI interface. Reliable adhesion of thin-film metallization to substrate has been proven using SiC, improving the potential transfer of micro-fabricated neural electrodes for chronic clinical applications.

bioengineering↗

bioRxiv2018

A closed-loop hand prosthesis with simultaneous intraneural tactile and position feedback

Current myoelectric prostheses allow upper-limb amputees to regain voluntary motor control of their artificial limb by exploiting residual muscle function in the forearm1. However, the over-reliance on visual cues resulting from a lack of sensory feedback is a common complaint2,3. Recently, several groups have provided tactile feedback in upper-limb amputees by using implanted electrodes4,5,6,7,8, surface nerve stimulation9,10 or sensory substitution11,12. These approaches have led to improved function and prosthesis embodiment4,5,6,7,13,14. Nevertheless, the provided information remains limited to a subset of the rich sensory cues available to healthy individuals. More specifically, proprioception, the sense of limb position and movement, is predominantly absent from current systems. Here we show that sensory substitution based on intraneural stimulation can deliver position feedback in real-time and in conjunction with somatotopic tactile feedback. This approach allowed two trans-radial amputees to regain high and close-to-natural remapped proprioceptive acuity, with a median joint angle reproduction accuracy of 9.1{degrees} and a median threshold to detection of passive movements of 9.5{degrees}, which was compatible with results obtained in healthy subjects15,16,17. The simultaneous delivery of position information and somatotopic tactile feedback allowed both amputees to discriminate object size and compliance with high levels of accuracy (75.5%). These results demonstrate that touch information delivered via somatotopic neural stimulation and position information delivered via sensory substitution can be exploited simultaneously and efficiently by trans-radial amputees. This study paves the way towards more sophisticated bidirectional bionic limbs conveying rich, multimodal sensations.

neuroscience↗