Electrical Stimulation of Distal Tibial Nerve During Stance Phase of Walking May Reverse Effects of Unilateral Paw Pad Anesthesia in the Cat.

Cutaneous feedback from feet is involved in regulation of muscle activity during locomotion, and the lack of this feedback results in motor deficits. We tested the hypothesis that locomotor changes caused by local unilateral anesthesia of paw pads in the cat could be reduced/reversed by electrical stimulation of cutaneous and proprioceptive afferents in the distal tibial nerve during stance. Several split-belt conditions were investigated in four adult female cats.

Analyzing the Effects of Parameters for Tremor Modulation via Phase-Locked Electrical Stimulation on a Peripheral Nerve.

(1) Background: Non-invasive neuromodulation is a promising alternative to medication or deep-brain stimulation treatment for Parkinson's Disease or essential tremor. In previous work, we developed and tested a wearable system that modulates tremor via the non-invasive, electrical stimulation of peripheral nerves. In this article, we examine the proper range and the effects of various stimulation parameters for phase-locked stimulation.

Fitts' Law Based Performance Metrics to Quantify Tremor in Individuals With Essential Tremor.

Current methods of evaluating essential tremor (ET) either rely on subjective ratings or use limited tremor metrics (i.e., severity/amplitude and frequency).

Differential cardiovascular responses to cutaneous afferent subtypes in a nociceptive intersegmental spinal reflex.

Electrical stimulation to segmental dorsal cutaneous nerves (DCNs) activates a nociceptive sensorimotor reflex and the same afferent stimulation also evokes blood pressure (BP) and heart rate (HR) responses in rats. To investigate the relationship between those cardiovascular responses and the activation of nociceptive afferents, we analyzed BP and HR responses to electrical stimulations at each DCN from T6 to L1 at 0.5 mA to activate A-fiber alone or 5 mA to activate both A- and C-fibers at different frequencies.

Cutaneous sensory feedback from paw pads affects lateral balance control during split-belt locomotion in the cat.

Cutaneous sensory feedback from the paw pads plays an important role in regulating body balance, especially in challenging environments like ladder or slope walking. Here, we investigated the contribution of cutaneous sensory feedback from the paw pads to balance control in cats stepping on a split-belt treadmill. Forepaws and hindpaws were anesthetized unilaterally using lidocaine injections.

Temporal and spatial dynamics of spinal sensorimotor processing in an intersegmental cutaneous nociceptive reflex.

The cutaneus trunci muscle (CTM) reflex produces a skin "shrug" in response to pinch on a rat's back through a three-part neural circuit: ) A-fiber and C-fiber afferents in segmental dorsal cutaneous nerves (DCNs) from lumbar to cervical levels, ) ascending propriospinal interneurons, and ) the CTM motoneuron pool located at the cervicothoracic junction. We recorded neurograms from a CTM nerve branch in response to electrical stimulation. The pulse trains were delivered at multiple DCNs (T-L), on both sides of the midline, at two stimulus strengths (0.

A Prototype of a Neural, Powered, Transtibial Prosthesis for the Cat: Benchtop Characterization.

We developed a prototype of a neural, powered, transtibial prosthesis for the use in a feline model of prosthetic gait. The prosthesis was designed for attachment to a percutaneous porous titanium implant integrated with bone, skin, and residual nerves and muscles. In the benchtop testing, the prosthesis was fixed in a testing rig and subjected to rhythmic vertical displacements and interactions with the ground at a cadence corresponding to cat walking.

Optimization of Stimulation Parameters for Targeted Activation of Multiple Neurons Using Closed-Loop Search Methods.

Differential activation of neuronal populations can improve the efficacy of clinical devices such as sensory or cortical prostheses. Improving stimulus specificity will facilitate targeted neuronal activation to convey biologically realistic percepts. In order to deliver more complex stimuli to a neuronal population, stimulus optimization techniques must be developed that will enable a single electrode to activate subpopulations of neurons.

Longitudinal wearable tremor measurement system with activity recognition algorithms for upper limb tremor.

Assessments of tremor characteristics by movement disorder physicians are usually done at single time points in clinic settings, so that the description of the tremor does not take into account the dependence of the tremor on specific behavioral situations. Moreover, treatment-induced changes in tremor or behavior cannot be quantitatively tracked for extended periods of time. We developed a wearable tremor measurement system with tremor and activity recognition algorithms for long-term upper limb behavior tracking, to characterize tremor characteristics and treatment effects in their daily lives.

A Stretchable Microneedle Electrode Array for Stimulating and Measuring Intramuscular Electromyographic Activity.

We have developed a stretchablemicroneedle electrode array (sMEA) to stimulate andmeasure the electrical activity of muscle across multiple sites. The technology provides the signal fidelity and spatial resolution of intramuscular electrodesacross a large area of tissue. Our sMEA is composed of a polydimethylsiloxane (PDMS) substrate, conductive-PDMS traces, and stainless-steel penetrating electrodes.

Quantitative assessment of arm tremor in people with neurological disorders.

Abnormal oscillatory movement (i.e. tremor) is usually evaluated with qualitative assessment by clinicians, and quantified with subjective scoring methods.

A three-dimensional image processing program for accurate, rapid, and semi-automated segmentation of neuronal somata with dense neurite outgrowth.

Three-dimensional (3-D) image analysis techniques provide a powerful means to rapidly and accurately assess complex morphological and functional interactions between neural cells. Current software-based identification methods of neural cells generally fall into two applications: (1) segmentation of cell nuclei in high-density constructs or (2) tracing of cell neurites in single cell investigations. We have developed novel methodologies to permit the systematic identification of populations of neuronal somata possessing rich morphological detail and dense neurite arborization throughout thick tissue or 3-D in vitro constructs.

Enabling techniques for in vitro studies on mammalian spinal locomotor mechanisms.

The neonatal rodent spinal cord maintained in vitro is a powerful model system to understand the central properties of spinal circuits generating mammalian locomotion. We describe three enabling approaches that incorporate afferent input and attached hindlimbs. (i) Sacral dorsal column stimulation recruits and strengthens ongoing locomotor-like activity, and implementation of a closed positive-feedback paradigm is shown to support its stimulation as an untapped therapeutic site for locomotor modulation.

Selective stimulation of the spinal cord surface using a stretchable microelectrode array.

By electrically stimulating the spinal cord, it is possible to activate functional populations of neurons that modulate motor and sensory function. One method for accessing these neurons is via their associated axons, which project as functionally segregated longitudinal columns of white-matter funiculi (i.e.

An effective lift-off method for patterning high-density gold interconnects on an elastomeric substrate.

are effectively patterned on an elastomeric substrate. A 3cm cable of ten gold wires with 10μm width and 20μm pitch is achieved, successfully demonstrating density increases of more than one order of magnitude from previously established work. Many applications in the fields of stretchable electronics and conformable neural interfaces will benefit from these fabrication developments.

Interleaved multichannel epimysial stimulation for eliciting smooth contraction of muscle with reduced fatigue.

Functional electrical stimulation (FES) refers to the method by which sensory or motor functionality is restored through the use of coordinated stimulation of tissue. Our group has developed a mechanically conformable multielectrode array (cMEA) that can stimulate and record from the surface of muscles with high fidelity and low invasiveness, making the device well suited for various FES applications. The research presented here investigates the feasibility of using a cMEA to deliver asynchronous spatiotemporal stimulation patterns epimysially (on the surface of muscles).

High-density stretchable electronics: toward an integrated multilayer composite.

High-density stretchable electronics is achieved using multilayer interconnects on an elastomeric substrate. Two major challenges associated with stretchable electronics—increasing integration density and improving electrical bonding—have been addressed by our innovative multilayer via-bonding technology. The resulting multichip-module architecture provides an elastic, high-density solution for numerous potential applications.

A PDMS-based conical-well microelectrode array for surface stimulation and recording of neural tissues.

A method for fabricating polydimethylsiloxane (PDMS) based microelectrode arrays (MEAs) featuring novel conical-well microelectrodes is described. The fabrication technique is reliable and efficient, and facilitates controllability over both the depth and the slope of the conical wells. Because of the high-PDMS elasticity (as compared to other MEA substrate materials), this type of compliant MEA is promising for acute and chronic implantation in applications that benefit from conformable device contact with biological tissue surfaces and from minimal tissue damage.

PDMS-based conformable microelectrode arrays with selectable novel 3-D microelectrode geometries for surface stimulation and recording.

A method for fabricating polydimethylsiloxane (PDMS) based conformable microelectrode arrays (MEAs) with selectable novel 3-D microelectrode geometries is presented. Simply recessed, conically recessed, exponentially recessed, and protruded-well microelectrodes have been fabricated on the MEA with a diameter as small as 10microm. 3-D microelectrode geometry parameters (recess depth, recess slope & profile, and protrusion/planar) can be controlled independently during fabrication.

Implementation of integratable PDMS-based conformable microelectrode arrays using a multilayer wiring interconnect technology.

To meet the emerging demand of high-throughput intimate interfaces in neuroscience research and neural prosthetics, a multilayer wiring interconnect technology for implementing high-density, integratable polydimethylsiloxane (PDMS) based conformable microelectrode arrays (MEAs) is developed. This technology has two parts: first, multilayer interconnects are fabricated within PDMS, which provides the potential for implementing high-density, large-capacity PDMS-based MEAs; second, interconnects are fabricated between PDMS and a substrate material, e.g.

Neuromechanical tuning of nonlinear postural control dynamics.

Postural control may be an ideal physiological motor task for elucidating general questions about the organization, diversity, flexibility, and variability of biological motor behaviors using nonlinear dynamical analysis techniques. Rather than presenting "problems" to the nervous system, the redundancy of biological systems and variability in their behaviors may actually be exploited to allow for the flexible achievement of multiple and concurrent task-level goals associated with movement. Such variability may reflect the constant "tuning" of neuromechanical elements and their interactions for movement control.

A retrofitted neural recording system with a novel stimulation IC to monitor early neural responses from a stimulating electrode.

Extracellular electrical stimulation is increasingly used for in vitro neural experimentation, including brain slices and cultured cells. Although it is desirable to record directly from the stimulating electrode, relatively high stimulation levels make it extremely difficult to record immediately after the stimulation. We have shown that this is feasible by a stimulation system (analog IC) that includes the feature of active electrode discharge.

Experimental platform for the study of region specific excitation and inhibition in neural tissue.

Willfully controlling the focus of an extracellular stimulus remains a significant challenge in the development of neural prosthetics and therapeutic devices. In part, this is due to the fact that experimental validation of the evoked response to stimuli is an arduous and time-consuming task. The development of a high-throughput data acquisition and analysis tool would greatly facilitate the design of spatially selective stimulation protocols.

Passive dynamics of a hybrid neuromechanical joint incorporating living muscle.

We have developed a hybrid neuromechanical joint to investigate the nonlinear properties of muscle in a physiologically relevant context. We constructed the hybrid system by connecting a live frog gastrocnemius muscle to a joint which is simulated as an inverted pendulum. We first tested this hybrid system with a spring as the actuator to ensure that the perturbation-response trajectories using living muscle would accurately describe the mechanical properties of the muscle.