Swathi Sheshadri

Progress of Flexible Electronics in Neural Interfacing - A Self-Adaptive Non-Invasive Neural Ribbon Electrode for Small Nerves Recording.

A novel flexible neural ribbon electrode with a self-adaptive feature is successfully implemented for various small nerves recording. As a neural interface, the selective recording capability is characterized by having reliable signal acquisitions from the sciatic nerve and its branches such as the peroneal nerve, the tibial nerve, and the sural nerve.

Flexible Epineural Strip Electrode for Recording in Fine Nerves

This paper demonstrates flexible epineural strip electrodes (FLESE) for recording from small nerves. Small strip-shaped FLESE enables us to easily and closely stick on various sized nerves for less damage in a nerve and optimal recording quality. In addition, in order to enhance the neural interface, the gold electrode contacts were coated with carbon nanotubes, which reduced the impedance of the electrodes. We used the FLESEs to record electrically elicited nerve signals (compound neural action potentials) from the sciatic nerve in rats. Bipolar and differential bipolar configurations for the recording were investigated to optimize the recording configuration of the FLESEs. The successful results from differential bipolar recordings showed that the total length of FLESEs could be further reduced, maintaining the maximum recording ability, which would be beneficial for recording in very fine nerves. Our results demonstrate that new concept of FLESEs could play an important role in electroceuticals in near future.

Mapping of Small Nerve Trunks and Branches Using Adaptive Flexible Electrodes

Selective stimulation is delivered to the sciatic nerve using different paris of contacts on a split‐ring electrode, while simulatneous recordings are acquired by the neural ribbon electrodes on three different branches. Two hook electrodes are also implanted in the muscle to monitor the activated muscle responses. It shows that the high precision implantation of electrodes, increases the efficacy and reduces the incidence of side effects.

Neural prosthesis for motor function restoration in upper limb extremity

Restoration of motor function in cases of peripheral nerve injury is a challenging problem. Although peripheral nerves do regenerate, the time required for peripheral nerves to regenerate often causes atrophy to occur in the muscles before they can be re-innervated. This paper presents a solution through proximal recording of nerve signals and distal muscle stimulation. A fully implantable hardware architecture is described that can be operated by means of inductive power and MICS band data transmission schemes. Preliminary experiments and validation studies are reported with non-human primates based on recordings in the median nerve, stimulation of hand muscles, and task decoding and classification. This approach shows promise in creating a neural prosthesis capable of restoring hand movements in patients with upper limb peripheral nerve injuries.

Self-organization of "fibro-axonal" composite tissue around unmodified metallic micro-electrodes can form a functioning interface with a peripheral nerve: A new direction for creating long-term neural interfaces.

A long‐term peripheral neural interface is an area of intense research. The use of electrode interfaces is limited by the biological response to the electrode material.

An intrafascicular electrode with integrated amplifiers for peripheral nerve recording

Thin-film longitudinal intrafascicular electrodes (tf-LIFE) are widely used for peripheral nerve recordings. tf-LIFEs are also promising electrodes for neural signal acquisition in future peripheral nerve prostheses. However, common mode signal interference, and electrical artifacts originating from long wire leads and wire movement are known problems encountered when using such electrodes, which lead to degradation in the recording quality. Here, we report an active tf-LIFE electrode implemented by integrating a neural amplifier chip die in close proximity to a tf-LIFE electrode. Consuming only 1mW and measuring 37 mm×7.2 mm×2.4 mm, this active tf-LIFE electrode creates a reliable connection and considerably shortens the distance between the electrode site and neural amplifier. This active electrode has demonstrated repeatable in-vivo recordings of compound action potentials from the rat sciatic nerve. Our results show that this electrode is suitable for repeated in-vivo recordings of compound action potentials from nerves in applications such as peripheral and visceral nerve interfaces that require low-noise stable nerve recordings.

Selective stimulation of peripheral motor nerve using a flexible split-ring electrode

Selective fascicle stimulation is a requirement for the neuroprosthetic treatment of peripheral nerve injuries in order to achieve a proper functional recovery. Here we show that multi-contact polyimide-based flexible split-ring electrodes can provide selective motor stimulation of the rat sciatic nerve. Considering the results, these kinds of electrodes appear suitable for bidirectional nerve interfaces in chronic neuroprosthetic applications.

Classification of phases of hand grasp task by the extraction of miniature compound nerve action potentials (mCNAPs)

Interfacing with the nervous system to restore functional motor activity is a promising therapy to augment the classical surgical approaches to treating peripheral nerve injuries. Despite the advances in electrode microelectronics engineering, the challenge of extracting information from injured nerves to help restore motor function remains unsolved. Here we used waveform feature extraction and clustering techniques to identify a discrete set of events in intraneural recordings of the median nerve in a non-human primate (NHP) during grasping tasks. This analysis allowed the classification of the different phases of hand grasping. The waveform features were found to be significantly different for each phase of grasping. Since these waveforms can be seen as the minimal signal components that result from the activation of a group of nerve fibers, we denominated them miniature compound nerve action potentials (mCNAPs). The correlation between mCNAPs and the different stages of movement can be utilized in the near future to design high-performance neuroprosthetic therapies.

Flexible and self-adaptive neural ribbon with three-dimensional electrodes for sciatic nerve recording.

Various peripheral nerve interfaces have been developed in the last decades and transferred into neuroscientific researches or clinical applications. In this study, we present a novel flexible neural ribbon electrode that can achieve self-adaption to nerves in various diameters and have three dimensional (3D) contacts. Impedance spectroscopy of the neural ribbon electrode was carried out to determine its electrochemical characteristics during the recording. The recording capability of the neural ribbon on sciatic nerves with different diameter was demonstrated by successful signal acquisitions.