Selective Nerve Stimulation Research Articles

Conditioning stimulus can influence an external urethral sphincter contraction evoked by a magnetic stimulation

To study the effect of a conditioning stimulus on an external urethral sphincter (EUS)contraction evoked by a magnetic stimulation at different time intervals. Seven healthy male volunteers underwent EUS pressure measurement. At baseline, magnetic stimulation of the lumbosacral spinal cord above the motor threshold was performed and evoked EUS pressure responses were recorded. The lumbosacral magnetic stimulation was repeated with same intensity, while a selective electrical dorsal penile nerve stimulation below the bulbocavernosus reflex (BCR) threshold was preceding at five different intervals (10, 20, 30, 50, 100 msec). The protocol was performed with empty and full bladder (BLA), and baseline responses were statistically compared to those with combined stimulation. When the dorsal penile nerve electrical stimulation preceded the lumbosacral magnetic stimulation by 20 msec (P=0.0048), 50 msec (P=0.0039), or 100 msec (P=0.0002), the amplitudes of the EUS pressure response with empty BLA were significantly reduced compared to lumbosacral magnetic stimulation alone. With a filled BLA, the amplitudes of the EUS were significantly reduced only at an interval of 50 msec (P<0.0001). A conditional sensory pudendal stimulation seems to have the capacity to inhibit the external urethral sphincter contraction induced by a magnetic stimulation. The inhibitory effect seems to depend on the latency between the peripheral and lumbosacral stimulation as well as on the degree of BLA filling. It remains to be proved if the neuromodulative effect of the conditional stimulus occurs at a spinal or supraspinal level.

Modulation of visceral function by selective stimulation of the left vagus nerve in dogs.

The superficial regions of the left vagus nerves of a dog were selectively stimulated with 39-electrode spiral cuffs having 13 circumferential groups of three electrodes (GTE) to modulate the function of the innervated internal organs and glands. Under general anaesthesia, the cuffs were chronically implanted around the nerve in the neck in two adult Beagle dogs and remained viable for 16 months. The regions were stimulated with biphasic, rectangular current pulses (2 mA, 200 micros, 20 Hz) delivered to the group of GTE lying close to the region innervating the specific internal organs or glands. The results showed that specific electrode configurations had actions on the heart (GTE 9), lungs (GTE 4) and pressure in the urinary bladder (GTE 1). It was also shown that GTE no. 10 significantly modified the endocrine function of the pancreas. The results of this study clearly demonstrate that internal organs and glands can be selectively stimulated via the selective stimulation of innervating superficial regions of the autonomous peripheral nerve.

Eye movements evoked by selective saccular nerve stimulation in cats

Objective: Because of technical obstacles in controlling current spread to adjacent peripheral nerve, eye movements evoked by activation of the otolith organs have not been investigated in detail compared to eye movements evoked by activation of the canal organs. We attempted to solve this problem by applying more sensitive methods using fine needle and strictly controlling stimulus current intensity compare with filed potential for selective stimulation. Methods: Eye movements evoked by selective, unilateral saccular (SAC) nerve stimulation were investigated using both electrooculography (EOG) and video recording in decerebrated cats in the presence or absence of anesthesia. Electrical stimulation was applied to the SAC nerve through implanted acupuncture needles. Results: In the absence of anesthesia and with stimulus intensities less than (3.1±2.7)×N 1T, we found supraduction in both eyes or in either the ipsilateral or contralateral eye of different cats. We observed downward eye movements using a stronger stimulus intensity ((6.2±2.9)×N 1T). The threshold for downward eye movements was significantly greater than that for upward eye movements ( P<0.05). In anesthetized cats, only downward eye movements were observed when stimulus intensities less than 10×N 1T ((7.8±2.3)×N 1T) were used. Conclusion: These results confirm the known sacculo-ocular anatomical connections, which are involved predominantly in vertical eye movements. Because the sacculo-ocular connections are relatively weak, the normal supraduction evoked by SAC activation can be easily modified by factors such as level of anesthesia and the method of stimulation.

Optimal design method for selective nerve stimulation

AbstractThis paper discusses selective stimulation, which is a problem common to various electrical stimulation techniques. The induction of nerve activity by electrical stimulation is a technique which is widely used in medical and health care. In order to reduce unpleasant feelings during stimulation and to diversify the induced sensations, it is necessary to control the stimulus waveform and to design the electrode in appropriate ways. From the viewpoint of nerve stimulation, the above requirement can be interpreted as a selective stimulation problem in which the target nerve fiber is stimulated and the activities of other nerves are minimized. At the present stage of electrical stimulation, however, there is no means of representing selectivity of stimulation mathematically, although precise modeling of the stimulus site is possible. Consequently, the design for selective stimulation is based on trial and error. The purpose of this paper is to construct a mathematical framework for the design of selective stimulation. The requirement for selective stimulation is formulated as a quadratic programming problem which gives a route to the optimal stimulation technique. Several simple examples are solved, and the usefulness of the proposed method is shown through comparison to selective stimulation techniques that were proposed in the past. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(9): 62–72, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20098

Differential effect of nitric oxide synthase inhibition on sigmoid colon longitudinal and circular muscle responses to nicotine and nerve stimulation in vitro.

Nicotine has been shown to release nitric oxide from nerves in human sigmoid colon. This effect has been used to investigate the innervation and functional relationship of the longitudinal and circular muscle layers. Strips of longitudinal and circular muscle were obtained from 19 patients with colorectal cancer. The strips from ten patients were subjected to electrical field stimulation (EFS) in vitro using stimulus parameters for selective stimulation of nerves. The effect of nicotine 1-10 micromol/l on EFS responses was then measured in the presence and absence of a nitric oxide synthase inhibitor, nitro-L-arginine methyl ester (L-NAME) 200 micromol/l. The effect of nicotine on spontaneous activity was investigated in the muscle strips from the other nine patients. Both longitudinal and circular strips responded to EFS with contraction. The time to achieve a peak contractile response (time to peak; TTP) was significantly longer (P<0.001) in circular strips. L-NAME reduced the mean(s.e.m.) TTP in circular muscle from 23.3(2.0) to 17.2(1.5) s (P=0.007) and altered its pattern of response to resemble that of longitudinal muscle. Nicotine 10 micromol/l reduced the contraction to EFS in circular (P<0.001) but not in longitudinal (P=0.347) muscle. The nicotine-induced reduction in circular muscle contraction was blocked by L-NAME 200 micromol/l (P=0.005). These findings suggest that nitric oxide release on neural stimulation is greater in circular than in longitudinal muscle.

A novel alpha-conotoxin identified by gene sequencing is active in suppressing the vascular response to selective stimulation of sensory nerves in vivo.

We describe the identification of a conopeptide sequence in venom duct mRNA from Conus victoriae that suppresses a vascular response to pain in the rat. PCR-RACE was used to screen venom duct cDNAs for those transcripts that encode specific antagonists of vertebrate neuronal nicotinic acetylcholine receptors (nAChRs). One of these peptides, Vc1.1, was active as an antagonist of neuronal nAChRs in receptor binding and functional studies in bovine chromaffin cells. It also suppressed the vascular responses to unmyelinated sensory nerve C-fiber activation in rats. Such vascular responses are involved in pain transmission. Furthermore, its ability to suppress C-fiber function was greater than that of MVIIA, an omega-conotoxin with known analgesic activity in rats and humans. Vc1.1 has a high degree of sequence similarity to the alpha-conotoxin family of peptides and has the 4,7 loop structure characteristic of the subfamily of peptides that act on neuronal-type nAChRs. The results suggest that neuronal alpha-conotoxins should be further investigated with respect to their potential to suppress pain.

Selective stimulation of pig radial nerve: comparison of 12-polar and 18-polar cuff electrodes.

Aiming at the development of an implantable neuroprosthesis for restoration of hand function in tetraplegic patients (C5/C6), we examined and compared the stimulation performance of two different neural electrode designs. Our studies on the radial nerve of adult pigs proved the feasibility of selective control of different forearm muscles by using only one multichannel nerve cuff electrode. The results gained by applying a 12-polar cuff electrode design were poor, while the potential of an 18-polar design was very encouraging.

Neurographic assessment of lesions of single proper digital nerves

Objective: To investigate which strategy should be used to assess lesions of single proper digital nerves by means of nerve conduction studies. Methods: Comparison of the results of various orthodromic and antidromic tests with surface electrodes and needle electrodes for stimulation and recording in two patients with a lesion of a single proper digital nerve of the middle finger. Results: It is shown that orthodromic and antidromic nerve conduction tests over the wrist-finger segment yield misleading results because of innervation overlap, volume conduction and co-stimulation. These problems could be avoided by selective stimulation of common digital nerves distally in the palm of the hand and recording with ring electrodes around the relevant finger. Efficacy and selectivity of stimulation are verified by simultaneous recordings from the neighbouring fingers. Conclusion: Lesions of single volar proper digital nerves are by no means rare, but no nerve conduction studies have been published so far to assess such lesions adequately. A novel, simple and reliable technique for this purpose is described.

Selective stimulation of cat sciatic nerve using an array of varying-length microelectrodes.

Restoration of motor function to individuals who have had spinal cord injuries or stroke has been hampered by the lack of an interface to the peripheral nervous system. A suitable interface should provide selective stimulation of a large number of individual muscle groups with graded recruitment of force. We have developed a new neural interface, the Utah Slanted Electrode Array (USEA), that was designed to be implanted into peripheral nerves. Its goal is to provide such an interface that could be useful in rehabilitation as well as neuroscience applications. In this study, the stimulation capabilities of the USEA were evaluated in acute experiments in cat sciatic nerve. The recruitment properties and the selectivity of stimulation were examined by determining the target muscles excited by stimulation via each of the 100 electrodes in the array and using force transducers to record the force produced in these muscles. It is shown in the results that groups of up to 15 electrodes were inserted into individual fascicles. Stimulation slightly above threshold was selective to one muscle group for most individual electrodes. At higher currents, co-activation of agonist but not antagonist muscles was observed in some instances. Recruitment curves for the electrode array were broader with twitch thresholds starting at much lower currents than for cuff electrodes. In these experiments, it is also shown that certain combinations of electrode pairs, inserted into an individual fascicle, excite fiber populations with substantial overlap, whereas other pairs appear to address independent populations. We conclude that the USEA permits more selective stimulation at much lower current intensities with more graded recruitment of individual muscles than is achieved by conventional cuff electrodes.

Conditioning of heteronymous H reflex in human temporalis muscle by stimulation of perioral afferents.

A heteronymous H reflex in the temporalis muscle can be elicited by selective stimulation of the masseteric nerve. The present study aimed at defining the optimal amplitude of the H reflex to detect inhibitory changes induced by stimulation of the perioral afferents and at providing new information on the control of masticatory muscles. Sixteen healthy volunteers participated in the experiment. A conditioning stimulus (CS) to the perioral skin was applied at various delays before an ipsilateral selective masseteric nerve stimulation (test stimulus: TS) while the subject was clenching the teeth at 25% of the maximal voluntary contraction. Two intensities of CS and TS were employed, high and low. The peak-to-peak amplitude of the H reflex (TS) and the root-mean-square value of the preceding electromyography were measured and the data analyzed by three-way analysis of variance and Tukey's posthoc tests. For both intensities used the heteronymous H reflex in the temporalis muscle was significantly decreased by prior activation of perioral afferents for delays from 5 to 60 ms. With a delay of 5 and 35 ms the preceding EMG level was not changed, while it was reduced at 20 and 60 ms delay. The intensities used to elicit the heteronymous H reflex of the temporalis muscle were appropriate to detect a reduction in motoneuron excitability. The reduction in the H reflex without a change in the preceding EMG at 5 and 35 ms delays could be due to presynaptic inhibition of the masseteric afferents exerted by the ipsilateral perioral afferents.

An implant for chronic selective stimulation of nerves

An implantable stimulator system has been developed for nerve stimulation. The system is capable of stimulating selectively, either by fibre position, fibre size or by sending action potentials in one direction only, based on the use of nerve cuffs. The stimulator produces either quasi-trapezoidal current pulses, to allow anodal blocking, or conventional rectangular-shaped current pulses, of amplitude 20 μA to 5 mA (in 20 μA steps) with duration of 16 μs to 1 ms (in 8 μs steps). For safety, both active and passive charge balancing is used. The amplitude of the active charge-balancing phase can be varied between 1/7 and 1/47 of the pulse amplitude. During manufacture, each implant is customised so as to drive either 6 quasi-tripolar (dipolar), 4 tripolar or 2 pentapolar cuffs. Possible applications of the device are: improved defaecation and bladder voiding after spinal cord injury, by stimulation of the sacral motor roots; neuromodulation to reduce hyperreflexia without concomitant muscle contractions; in stroke patients, to enable balanced inversion–eversion while dorsiflexing the ankle by stimulating the peroneal nerve. It may also be used in chronic animal experiments. This paper describes the implant system, its hardware and communication protocol, and shows results from in vitro tests of the device and the first acute anodal-blocking experiments in pigs.

Spatial distribution of semicircular canal nerve evoked monosynaptic response components in frog vestibular nuclei

Most second-order vestibular neurons receive a canal-specific monosynaptic excitation, although the central projections of semicircular canal afferents overlap extensively. This remarkable canal specificity prompted us to study the spatial organization of evoked field potentials following selective stimulation of individual canal nerves. Electrically evoked responses in the vestibular nuclei were mapped systematically in vitro. Constructed activation maps were superimposed on a cytoarchitectonically defined anatomical map. The spatial activation maps for pre- and postsynaptic response components evoked by stimulation of a given canal nerve were similar. Activation maps for monosynaptic inputs from different canals tended to show a differential distribution of their peak amplitudes, although the overlap was considerable. Anterior vertical canal signals peaked in the superior vestibular nucleus, posterior vertical canal signals peaked in the descending and in the dorsal part of the lateral vestibular nucleus, whereas horizontal canal signals peaked in the descending and in the ventral part of the lateral vestibular nucleus. A similar, differential but overlapping, spatial organization of the canal inputs was described also for other vertebrates, suggesting a crude but rather conservative topographical organization of semicircular canal nerve projections within the vestibular nuclei. Differences in the precision of topological representations between vestibular and other sensory modalities are discussed.

A Novel Scheme for the Selective Stimulation of Nerve Fibers Using Nonlinear Properties of Action Potentials

In this paper, we propose a novel technique for selective stimulation of nerve fibers. We show that a set of point electrodes arranged in the 3-D space around a nerve trunk can be used to systematically synthesize highly useful activation patterns within the nerve, by exploiting the spatial arrangement of the electrodes and the excitation currents. Using such activation patterns, we present a novel scheme to selectively stimulate nerve fibers, based on the nonlinear properties of action potential generation. We illustrate the developed techniques via computer simulations of a nerve trunk consisting of a large number of nerve fibers. The results indicate that the proposed technique has great potential to achieve position selective stimulation of nerve in FES.

INFLUENCE OF SACRAL NEUROMODULATION ON ELECTROSENSATION OF THE LOWER URINARY TRACT

We prospectively investigated whether neuromodulation of the S3 root influences the sensory threshold to electrical stimulation in the lower urinary tract. The study included 7 women and 3 men receiving S3 neuromodulation at 210 msec. and 25 Hz. with the Interstim PNE system for a mean of 5 days. Neuromodulation was done unilaterally in 6 cases and bilaterally in 4. The sensory threshold was determined by electrodes placed randomly against the mucosa of the empty bladder on the left and right sides, in the urethra in women, and in the prostatic and penile urethra in men. Thresholds were measured at each location with neuromodulation on and off. With bilateral neuromodulation on all 4 patients had a lower bladder threshold than with neuromodulation off. In unilateral neuromodulation the threshold was significantly lower during neurostimulation on the ipsilateral side. There was no effect on the threshold on the arm or in the urethra. The effect was noted in patients in whom neuromodulation was and was not clinically successful. Neuromodulation on S3 influences the nervous system involved in electrosensation of the bladder but not the skin afferent innervation or the nerves involved in urethral electrosensation. These data support the hypothesis that S3 neurostimulation is effective mainly through the afferent nervous system in the pelvic nerves.

Nerve Stimulation With A Multi-Contact Cuff Electrode: Validation Of Model Predictions

The recruitment characteristics of muscle selective nerve stimulation by a multi-contact nerve cuff electrode, as predicted by computer modeling, have been investigated in acute experiments on rabbits. A nerve cuff containing five or six dot electrodes was placed around the sciatic nerve in five rabbits. M-waves were recorded with wire electrodes from the lateral gastrocnemius, soleus, tibialis anterior, and extensor digitorum longus muscles. The muscle recruitment performances of three contact configurations (monopole, transverse bipole, transverse tripole) were compared. The selectivity was quantified by the recruitment of two muscles (one extensor and one flexor) in response to a particular stimulus. The results showed that only in a few cases, transverse bi- and tripolar stimulation provided a better selectivity than monopolar stimulation. Neither of the two extensors, nor of the two flexors could be stimulated separately. In accordance with the results of the modeling studies, bi- and tripolar stimulation required higher stimulus currents than monopolar stimulation, whereas maximum recruitment and slopes of recruitment curves were lower. The rabbit sciatic nerve appears to be a less suitable preparation for reproducible selectivity experiments, due to the variability in the number and size of the fascicles and their position in this nerve.

Electronic design of a multichannel programmable implant for neuromuscular electrical stimulation.

An advanced stimulator for neuromuscular stimulation of spinal cord injured patients has been developed. The stimulator is externally controlled and powered by a single encoded radio frequency carrier and has four independently controlled bipolar stimulation channels. It offers a wide range of reprogrammability and flexibility, and can be used in many neuromuscular electrical stimulation applications. The implant system is adaptable to patient's needs and to future developments in stimulation algorithms by reprogramming the stimulator. The stimulator is capable of generating a wide range of stimulation waveforms and stimulation patterns and therefore is very suitable for selective nerve stimulation techniques. The reliability of the implant has been increased by using a forward error detection and correction communication protocol and by designing the chip for structural testability based on scan test approach. Implemented testability scheme makes it possible to verify the complete functionality of the implant before and after implantation. The stimulators architecture is designed to be modular and therefore its different blocks can be reused as standard building blocks in the design and implementation of other neuromuscular prostheses. Design for low-power techniques have also been employed to reduce power consumption of the electronic circuitry.

EXTRADURAL COLD BLOCK FOR SELECTIVE NEUROSTIMULATION OF THE BLADDER: DEVELOPMENT OF A NEW TECHNIQUE

Purpose Cryotechnique for selective block of the urethral sphincter and simultaneous activation of the bladder was developed to achieve physiological micturition during sacral anterior root stimulation (SARS). Materials and Methods In ten foxhounds SARS of S2 was carried out while extradurally both spinal nerves S2 were cooled down from positive 25C in a stepwise fashion until a sphincter block was observed. Subsequently, SARS of S2 was performed while the pudendal nerves were cooled down from +15C. The effects of spinal and pudendal nerve cold block on the urethral sphincter and bladder during SARS and the recovery time were monitored by urodynamic investigation. Results A complete cold block of the urethral sphincter during spinal nerve cooling was achieved in all cases. During pudendal nerve cooling, the sphincter was completely blocked in two, and incompletely blocked in four dogs. Cold block temperature of the spinal nerves averaged +11.7C and of the pudendal nerves +6.2C. During SARS and spinal nerve cooling, an increase in intravesical pressure up to 13 cm. water was recognized, and recovery time was an average 6.6 minutes. Intravesical pressure remained unchanged during pudendal nerve cooling, with recovery time being less than 1 minute. The cold block was always reversible. Conclusions Cryotechnique is an excellent method for selective and reversible block of the urethral sphincter during SARS to avoid detrusor-sphincter-dyssynergia. The application of cryotechnique in functional electrical stimulation leads to an improvement of quality of life in para- or tetraplegic patients because of selective nerve stimulation with optimization of micturition, standing, walking and grasping and does so without the necessity of surgical dorsal root rhizotomy.

Multielectrode Nerve Cuff Stimulation of the Median Nerve Produces Selective Movements in a Raccoon Animal Model

In this study, an electrode system consisting of twelve small platinum dot electrodes imbedded in a spiral silicone rubber insulating cuff was used to investigate the feasibility of selective (regional) stimulation of the median nerves of the raccoon. Acute experiments in four raccoons consisted of functional response observations, isometric force recordings from tendon attachments and postmortem fascicular mapping. Functional responses (elbow, wrist and/or digit flexion, pronation and/or thumb abduction) to selective stimulation were noted as dependent upon cuff electrode configuration (longitudinal tripole with and without field steering, as well as a transverse bipolar arrangement) and current level (threshold, 1/2 maximal, maximal). Muscle force recruitment curves (force as a function of stimulus amplitude) were plotted for flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, palmaris longus and pronator teres of three raccoons. Fascicular maps at the level of the nerve cuff were created indicating the approximate position of innervation to each of the aforementioned muscles, as well as other innervation such as paw fascicles, sensory fascicles, and elbow innervation (such as coracobrachialis). The greatest selectivity was observed at or near threshold current levels. In all tour raccoons studied, a threshold electrode choice and stimulation strategy could be identified enabling selective production of either digit flexion, wrist flexion and/or digit and wrist flexion. It was possible to elicit a selective pronation response at threshold in three of the four animals. Selective elbow flexion at threshold could be produced in all four experiments. With stronger currents, additional movements were usually induced. The raccoon therefore appears to be a suitable, if challenging, animal model for further development of not only nerve cuff electrode approaches but perhaps other stimulation electrode technologies prior to human neuroprosthetic studies. (J Spinal Cord Med 1997; 20:233-243)

Inflammation impairs neurally mediated responses to electrical field stimulation in isolated strips of human gallbladder muscle.

Strips from human gallbladder removed at surgery were exposed to cholecystokinin octopeptide CCK-OP 15 nM and were subjected to electrical field stimulation (EFS) in vitro using parameters for selective stimulation of nerves (5- to 10-sec trains of 0.3-msec pulses at 10 Hz). An adjacent strip from the same specimen was processed for histological examination. These preparations were given a numerical score for inflammatory change. The strength of contraction in response to CCK-OP was inversely related to the severity of inflammation. Gallbladders with no response to EFS had a higher inflammation score (median 11, range 5-16) than those with a response (median 7, range 3-12). We conclude that inflammatory changes in human gallbladder impair responses to neural and hormonal stimulation, but we are unable to determine unequivocally in this study whether this is a result of damage to nerves or muscle cells. However, the observation that some strips were able to contract in response to CCK-OP but not to neural stimulation suggests the possibility of neural damage in gallbladder inflammation.

Nervous control of juvenile hormone biosynthesis in Locusta migratoria.

In Locusta migratoria migratorioides R. and F., two types of brain neurons innervate the juvenile hormone (JH)-producing corpora allata (CA). Thirteen cells in each pars lateralis (PL) innervate the ipsilateral CA, while four cells (two in each PL) innervate both glands. We investigated possible influences of these two neuronal types on JH production by a newly developed method. A radiochemical assay was used to measure hourly JH production by a CA with intact nerve connections to the brain. Then, changes in hormone production due to selective nerve stimulation or transection were assessed. In control preparations JH production per h remained approximately constant for at least 9 h. Simultaneous electrical stimulation of all neurons innervating one CA (i.e., 13 ipsilateral plus 4 bilaterally innervating cells) always inhibited JH production, while their transection led to a rapid progressive increase in JH biosynthesis in CA from females with oocytes longer than 4.5 mm. Thus, there is strong neurally mediated inhibition of the CA at certain phases of the vitellogenic cycle. The dramatic effects of nerve transection show that in vitro rates of JH production are an unreliable indicator of in vivo levels. Selective stimulation of the four neurons innervating both CA suggests that they do modulate JH biosynthesis but the effect varies qualitatively depending on the phase of the vitellogenic cycle.