Ken Yoshida

Bio: Ken Yoshida is an academic researcher from Indiana University – Purdue University Indianapolis. The author has contributed to research in topics: Spike sorting & Muscle spindle. The author has an hindex of 33, co-authored 124 publications receiving 3651 citations. Previous affiliations of Ken Yoshida include Aalborg University & University of Indianapolis.

Assessment of Biocompatibility of Chronically Implanted Polyimide and Platinum Intrafascicular Electrodes

Abstract: Longitudinal intrafascicular electrodes (LIFEs) are electrodes designed to be placed inside the peripheral nerve to improve stimulation selectivity and to increase the recording signal-to-noise ratio. We evaluated the functional and morphological effects of either Pt wire LIFEs or polyimide-based thin-film LIFEs implanted in the rat sciatic nerve for 3 mo. The newly designed thin-film LIFEs are more flexible, can be micromachined and allow placement of more active electrode sites than conventional Pt LIFEs. Functional results at 1 mo indicated an initial decline in the nerve conduction velocity and in the amplitude of muscle responses, which recovered during the following 2 mo towards normal values. Morphological results showed that both types of LIFEs induced a mild scar response and a focal but chronic inflammatory reaction, which were limited to a small area around the electrode placed in the nerve. Both types of LIFEs can be considered biocompatible and cause reversible, minimal nerve damage

Selective stimulation of peripheral nerve fibers using dual intrafascicular electrodes

Abstract: The authors have studied activation of nerve fibers by pairs of Pt-Ir wire electrodes implanted within single fascicles of the nerve innervating the gastrocnemius muscle in cats The purpose of this study was to determine if these intrafascicular electrodes can activate nerve fibers in different fascicles independently of each other and if they can also be used to activate separate subsets of axonal populations within a single fascicle The average overlap of activated nerve fiber populations was 55% between fascicles and 27% within a fascicle, indicating that such selective activation is possible with these electrodes >

A 32-site neural recording probe fabricated by DRIE of SOI substrates

Abstract: An all-dry silicon-etch based micromachining process for neural probes was demonstrated in the manufacture of a probe with a 32-site recording electrode array. The fork-like probe shafts were formed by double-sided deep reactive ion etching (DRIE) of a silicon-on-insulator (SOI) substrate, with the buried SiO2 layer acting as an etch stop. The shafts typically had the dimensions 5 mm × 25 μm × 20 μm and ended in chisel-shaped tips with lateral taper angles of 4°. An array of Ir electrodes, each 100 μm2, and Au conductor traces were formed on top of the shafts by e-beam evaporation. An accompanying interconnect solution based on flexible printed circuitry was designed, enabling precise and flexible positioning of the probes in neural tissue. SEM studies showed sharply defined probes and probe tips. The electrical yield and function were verified in bench-top measurements in saline. The magnitude of the electrode impedance was in the 1 MΩ range at 1 kHz, which is consistent with neurophysiological recordings.

Closed-loop control of ankle position using muscle afferent feedback with functional neuromuscular stimulation

Abstract: Describes a closed-loop functional neuromuscular stimulation system that uses afferent neural activity from muscle spindle fibers as feedback for controlling position of the ankle joint. Ankle extension against a load was effected by neural stimulation through a dual channel intrafascicular electrode of a fascicle of the tibial nerve that innervated the gastrocnemius muscle. Ankle joint angle was estimated from recordings of tibialis anterior and lateral gastrocnemius spindle fiber activity made with dual channel intrafascicular electrodes. Experiments were conducted in neurally intact anesthetized cats and in unanesthetized decerebrate cats to demonstrate the feasibility of this system. The system was able to reach and maintain a fixed target ankle position in the presence of a varying external moment ranging in magnitude between 7.3 and 22 N-cm opposing the action of the ankle extensor, as well as track a sinusoidal target ankle position up to a frequency of 1 Hz in the presence of a constant magnitude 22- or 37-N-cm external moment.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Large-scale recording of neuronal ensembles

Abstract: How does the brain orchestrate perceptions, thoughts and actions from the spiking activity of its neurons? Early single-neuron recording research treated spike pattern variability as noise that needed to be averaged out to reveal the brain's representation of invariant input. Another view is that variability of spikes is centrally coordinated and that this brain-generated ensemble pattern in cortical structures is itself a potential source of cognition. Large-scale recordings from neuronal ensembles now offer the opportunity to test these competing theoretical frameworks. Currently, wire and micro-machined silicon electrode arrays can record from large numbers of neurons and monitor local neural circuits at work. Achieving the full potential of massively parallel neuronal recordings, however, will require further development of the neuron–electrode interface, automated and efficient spike-sorting algorithms for effective isolation and identification of single neurons, and new mathematical insights for the analysis of network properties.

Metallic implant biomaterials

Abstract: Human tissue is structured mainly of self-assembled polymers (proteins) and ceramics (bone minerals), with metals present as trace elements with molecular scale functions. However, metals and their alloys have played a predominant role as structural biomaterials in reconstructive surgery, especially orthopedics, with more recent uses in non-osseous tissues, such as blood vessels. With the successful routine use of a large variety of metal implants clinically, issues associated with long-term maintenance of implant integrity have also emerged. This review focuses on metallic implant biomaterials, identifying and discussing critical issues in their clinical applications, including the systemic toxicity of released metal ions due to corrosion, fatigue failure of structural components due to repeated loading, and wearing of joint replacements due to movement. This is followed by detailed reviews on specific metallic biomaterials made from stainless steels, alloys of cobalt, titanium and magnesium, as well as shape memory alloys of nickel–titanium, silver, tantalum and zirconium. For each, the properties that affect biocompatibility and mechanical integrity (especially corrosion fatigue) are discussed in detail. Finally, the most critical challenges for metallic implant biomaterials are summarized, with emphasis on the most promising approaches and strategies.