Acute peripheral nerve recording characteristics of polymer-based longitudinal intrafascicular electrodes

Journal ArticleWe examined the recording characteristics of two different types of polymer-based longitudinal intrafascicular electrodes (LIFEs) in peripheral nerve: single-stranded (s-polyLIFEs) and multistranded (m-polyLIFEs). Recordings were also made from Pt-Ir wire-based electrodes (PtIrLIFEs) as a control. The electrodes were implanted in either tibial or medial gastrocnemius branches of the rabbit sciatic nerve, and in the sciatic nerve of rats. Recorded neural activity induced by manually elicited afferent neural activity showed that both polyLIFE versions performed comparably to PtIrLIFEs

Non-Invasive Sensory Input Results in Changes in Non-Painful and Painful Sensations in Two Upper-Limb Amputees

Designs of active prostheses attempt to compensate for various functional losses following amputation. Integration of sensory feedback with the functional control re-enables sensory interaction with the environment through the prosthetic. Besides the functional and sensory loss, amputation induces anatomical and physiological changes of the sensory neural pathways, both peripherally and centrally, which can lead to phantom limb pain (PLP). Additionally, referred sensation areas (RSAs) likely originating from peripheral nerve sprouting, regeneration, and sensory reinnervation may develop. RSAs might provide a non-invasive access point to sensory neural pathways that project to the lost limb. This paper aims to report on the sensory input features, elicited using non-invasive electrical stimulation of RSAs that over time alleviated PLP in two upper-limb amputees. The distinct features of RSAs and sensation evoked using mechanical and electrical stimuli were characterized for the two participants over a period of 7 and 9 weeks, respectively. Both participants received transradial and transhumeral amputation following traumatic injuries. In one participant, a relatively low but stable number of RSAs provided a large variety of types of evoked phantom hand (PH) sensations. These included non-painful touch, vibration, tingling, stabbing, pressure, warmth/cold as well as the perception of various positions and movements of the phantom hand upon stimulation. Discomforting and painful sensations were induced with both mechanical and electrical stimuli. The other participant had a relatively large number of RSAs which varied over time. Stimulation of the RSAs provided mostly non-painful sensations of touch in the phantom hand. Temporary PLP alleviation and a change in the perception of the phantom hand from a tight to a more open fist were reported by both participants. The specificity of RSAs, dynamics in perception of the sensory input, and the associated alleviation of PLP could be effectively exploited by designs of future active prostheses. As such, techniques for the modulation of the sensory input associated with paradigms from interaction with the environment may add another dimension of protheses towards integrating personalized therapy for PLP

Geometric Characterization of Local Changes in Tungsten Microneedle Tips after In-Vivo Insertion into Peripheral Nerves

Peripheral neural interfaces are used to connect the peripheral nervous system to high-tech robotic devices and computer interfaces. Soft materials are nowadays used to build the main structural part of these interfaces because they are able to mimic the mechanical properties of peripheral nerves. However, if on the one hand soft materials provide effective connections, reducing mechanical mismatch with nervous tissues and creating a close contact between active sites and neural fibers, on the other hand, most of them are not mechanically stable during implantation. As a consequence, tungsten (W) microneedles are used to insert soft neural interfaces, because they are able to pierce the peripheral nervous tissue because of their high stiffness. Nevertheless, this stiffness cannot prevent microneedles from local microscopic structural damage, even after successful insertions. In addition, the nature of this damage is not totally clear. Therefore, this work aimed at quantitatively investigating the phenomenological changes of the microneedles’ tip shape after insertion into the in vivo peripheral nerves. In particular, a quantification of the interactions between peripheral nerves and W microneedles was proposed through the Oliver-Pharr formula, and the interaction force was found to be directly proportional to the power < m > = 2.124 of the normalized indentation depth. Moreover, an experimental correlation between insertion force and the opening tip angle was described together with an assessment of the minimum diameter to effectively puncture the peripheral nervous tissue. Finally, a computational framework was presented to describe the local changes affecting the microneedles’ tip shape. This approach was able to detect a bulging phenomenon along with the microneedle tips with a characteristic amplitude of approximately 100 μm, and a folding phenomenon, with a characteristic mean amplitude of less than 20 μm, affecting the extreme ending sections of the microneedle tips. These geometrical changes were related to the synergistic action of interaction forces likely resulting in compression and elastic instability of the tip