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PubMed1984

Electrical stimulation to reduce chronic toe-flexor hypertonicity. A case report.

Electrical stimulation reduces hypertonicity, but the mechanism for the effectiveness is not well understood. In this particular case, electrical stimulation to the toe extensors resulted in inhibition of the toe-flexor hypertonicity. This phenomenon may be explained by Sherrington's theory of reciprocal inhibition. Liberson found that electrical stimulation of an agonist is associated with a concomitant inhibition of the antagonist in the healthy individual. I applied Liberson's findings in my treatment of the patient. By facilitating the toe extensors, and thus inhibiting the toe flexors, toe posturing improved considerably and allowed the patient volitionally to control his toes, which, in turn, improved his foot and toe comfort. Stimulation also allowed the patient to assume a plantigrade and forefoot weight-bearing position to improve his gait. This patient benefitted dramatically from the use of electrical stimulation in inhibiting hypertonicity, and I believe this modality may be helpful in other cases dealing with increased muscle tone. The patient will continue to be observed on a regular basis for reassessment of the long-term effects of electrical stimulation on hypertonicity and on the skin at the electrode sites.

Adult↗
PubMed1979

Vasoconstriction of the isolated communicating cerebral artery induced by field electrical stimulation.

The vasoconstrictor effect elicited by field electrical stimulation of the posterior communicating cerebral artery of the goat was analyzed before and after treatment with pharmacological agents to find out if the adrenergic system was involved in this response. For this purpose, trains of 300 square wave pulses (1-32 Hz, 0.5 msec.) at supramaximal voltage were applies to these arteries producing a frequency-dependent increase in tension. The vasoconstrictor response was significantly reduced by tetrodotoxin (3 x 10(-6) M), phentolamine (10(-6) M) and bretylium (5 x 10(-4) M), but it was not modified by cocaine (10(-6) M). The contraction produced by electrical stimulation of arterial segments from goats pretreated with reserpine (0.02 mg/kg/day for three days) and from goats on which a bilateral superior cervical gangliectomy had been performed 12 days previously, was significantly reduced as compared with controls. These results show that a large part of the vasoconstrictor response of the goat cerebral vessels to field electrical stimulation is mediated by an adrenergic mechanism.

Adrenergic Fibers↗
PubMed1999

A computational model of electrical stimulation of the retinal ganglion cell.

Localized retinal electrical stimulation in blind volunteers results in discrete round visual percepts corresponding to the location of the stimulating electrode. The success of such an approach to provide useful vision depends on elucidating the neuronal target of surface electrical stimulation. To determine if electrodes preferentially stimulate ganglion cells directly below them or passing fibers from distant ganglion cells, we developed a compartmental model for electric field stimulation of the retinal ganglion cell (RGC). In this model a RGC is stimulated by extracellular electrical fields with active channels and realistic cell morphology derived directly from a neuronal tracing. Three membrane models were applied: a linear passive model, a Hodgkin-Huxley model with passive dendrites (HH), and a model composed of all active compartments (FCM) with five nonlinear ion channels. Idealized monopolar point and disk stimulating electrodes were positioned above the cell. For the HH and FCM models, the position of lowest cathodal threshold to propagate an action potential was over the soma. Brief (100 microseconds) cathodic stimuli were 20% (HH with disk electrode) to 73% (FCM with point-source) more effective over the soma than over the axon. In the passive model, the axon is preferentially stimulated versus the soma. Although it may be possible to electrically stimulate RGC's near their cell body at lower thresholds than at their axon, these differences are relatively small. Alternative explanations should be sought to explain the focal perceptions observed in previously reported patient trials.

Action Potentials↗
PubMed2005

Cross-talk along gastrointestinal tract during electrical stimulation: effects and mechanisms of gastric/colonic stimulation on rectal tone in dogs.

Gastric electrical stimulation (GES) has been shown to alter motor and sensory functions of the stomach. However, its effects on other organs of the gut have rarely been investigated. The study was performed in 12 dogs implanted with two pairs of electrodes, one on the serosa of the stomach and the other on the colon. The study was composed of two experiments. Experiment 1 was designed to study the effects of GES on rectal tone and compliance in nine dogs compared with colonic electrical stimulation (CES). Rectal tone and compliance were assessed before and after GES or CES. Experiment 2 was performed to study the involvement of sympathetic pathway in 8 of the 12 dogs. The rectal tone was recorded for 30-40 min at baseline and 20 min after intravenous guanethidine. GES or CES was given for 20 min 20 min after the initiation of the infusion. It was found that both GES and CES reduced rectal tone with comparable potency. Rectal compliance was altered neither with GES, nor with CES. The inhibitory effect of GES but not CES on rectal tone was abolished by an adrenergic blockade, guanethidine. GES inhibited rectal tone with a comparable potency with CES but did not alter rectal compliance. The inhibitory effect of GES on rectal tone is mediated by the sympathetic pathway. It should be noted that electrical stimulation of one organ of the gut may have a beneficial or adverse effect on another organ of the gut.

Adrenergic Agents↗
PubMed1976

[The effect of low-frequency electric stimulation of the caudate nucleus on the electrical activity of the cortex and on the sleep-wakefulness cycle].

In cats, the effect of low-frequency electric stimulation of the caudate nucleus on electric activity of neo- and archipaleocortex and on wakefulness-sleep cycle, was studied. The data obtained suggest: 1) at threshold and suprathreshold single electric shocks applied to the caudate nucleus they evoked potential occurs more readily in the sensorimotor area of the neocortex than in the dorsal hippocampus. At 2-6/sec stimulation the evoked potentials in the hippocampus are facilitated and become very stable, whereas in the sensorimotor cortex the most obvious responses occur at the 6-8/sec frequency. However, the evoked potentials are variable in the sensorimotor cortex, and at prolonged 8-12/sec stimulation spindle activity soon develops; 2) behavioral correlate of the synchronized activity in the neo- and archipaleocortical structures during low-frequency stimulation of the caudate nucleus, may involve development of drowsiness with the cessation of stimulation, however, both the EEG and behavioral signs of the drowsiness disappear. The onset of drowsiness following withdrawal of the caudate stimulation, is a rare phenomenon only occurring because of an occasional coincidence of the stimulation with the spontaneous onset of natural sleep; 3) low-frequency caudate stimulation entailing the ECoG synchronization does not cause the transition of paradoxical phase into the slow-wave phase of sleep, and as soon as the stimulation ceases its normal structure recovers. However, if the stimulation of the caudate nucleus is repeated several times in one paradoxical phase, this would shorten the subsequent slow-wave phase and accelerate the onset of the next paradoxical phase; 4) prolonged low-frequency stimulation of the caudate nucleus causing the ECoG synchronization results in a considerable change of wakefulness-sleep cycle in the post-stimulation period: a decrease in the total time of slow-wave sleep due to shortening of its different phases, and an increase in the total amount of paradoxical sleep because of the onset of its phases is rendered more frequent. This effect is more obvious in the first half of the 8-hr cycle.

Animals↗
PubMed2004

Facilitatory effect on the motor cortex by electrical stimulation over the cerebellum in humans.

Electrical stimulation over the cerebellum is known to transiently suppress the contralateral motor cortex in humans. However, projections from the cerebellar nuclei to the primary motor cortex are disynaptic excitatory pathways through the ventral thalamus. In the present investigation we studied facilitatory effects on the motor cortical excitability elicited by electrical stimulation over the cerebellum by recording surface electromyographic (EMG) responses from the first dorsal interosseous (FDI) muscle in nine normal volunteers. For primary motor cortical activation magnetic stimuli were given over the contralateral hand motor area with a figure-of-eight shaped coil with a current to preferentially elicit I3-waves (test stimulus). For cerebellar stimulation high-voltage electric stimuli were given with an anode on the ipsilateral mastoid process and a cathode over the contralateral process as previously described (conditioning stimulus). The effect of conditioning-test interstimulus intervals was investigated. Anodal cerebellar stimuli increased the size of EMG responses to magnetic cortical stimulation at an interstimulus interval of 3 ms. Reversing the current of conditioning stimulus abolished the facilitation. The same (anodal) conditioning stimuli did not affect electrically evoked cortical responses. Based on the effective polarity of the conditioning stimulus and the time course of facilitation we consider that this effect is due to motor cortical facilitation elicited by activation of the excitatory dentatothalamocortical pathway at the deep cerebellar nuclei or superior cerebellar peduncle. We conclude that the motor cortical facilitation is evoked by cerebellar stimulation in humans.

Adult↗
PubMed1994

Diagnostic value of electrical stimulation of lumbosacral roots in radiculopathies.

Needle electrical stimulation of the lumbosacral roots at the laminar level of the Th12-L1 or L1-2 intervertebral spaces were performed in 24 normal subjects and 58 patients with various kinds of lumbar radiculopathy (unilateral L4, L5 and S1 herniated nucleus pulposus and lumber stenosis). The root stimulation method was compared with conventional needle EMG. Lumber electrical stimulation showed root abnormalities objectively in 80% of patients while the diagnostic value of needle EMG was 65%. Therefore, electrical root stimulation is superior to routine EMG for localizing lumbar root involvement. However, the only needle EMG demonstrated the root pathology in 7 cases (12%) and single electrophysiological abnormality was found by the root stimulation in 16 cases (27%). Thus, both electrophysiological methods should be complementary to each other in evaluation of the lumbar radioculopathy.

Action Potentials↗
PubMed1991

The renal response to electrical stimulation of renal efferent sympathetic nerves in the anaesthetized greyhound.

1. The effect of direct electrical stimulation of the renal efferent nerves upon renal haemodynamics and function was studied in greyhounds anaesthetized with chloralose and artificially ventilated. The left kidney was neurally and vascularly isolated, and perfused with blood from one of the femoral arteries at a constant pressure of 99 +/- 1 mmHg. Renal blood flow was measured with a cannulating electromagnetic flow probe placed in the perfusion circuit, glomerular filtration rate by creatinine clearance, urinary sodium excretion by flame photometry and solute excretion by osmometry. Beta-Adrenergic receptor activation was blocked by the infusion of dl-propranolol (17 micrograms kg-1 min-1). The peripheral ends of the ligated renal nerves were stimulated at 0.5, 1.0, 1.5 and 2.0 Hz. 2. At 0.5 Hz frequency only osmolar excretion was significantly reduced (10.3 +/- 3.2%, P less than 0.05, n = 6). Reductions in sodium excretion (53.6 +/- 8.5%, P less than 0.01, n = 6) and water excretion (26.9 +/- 8.0%, P less than 0.05, n = 6) and further reductions of osmolar excretion (20.7 +/- 3.7%, P less than 0.01, n = 6) were observed at 1.0 Hz; however, these were observed in the absence of significant changes in renal blood flow and glomerular filtration rate. Significant reductions were observed in glomerular filtration rate at 1.5 Hz (16.3 +/- 4.1%, P less than 0.02, n = 5) and in renal blood flow at 2.0 Hz (13.1 +/- 4.0%, P less than 0.05, n = 5). Further reductions in urine flow and sodium excretion were also observed at these higher frequencies. 3. These results clearly show that significant changes in renal tubular function can occur in the absence of changes in renal blood flow and glomerular filtration rate when the renal nerves are stimulated electrically from a zero baseline activity up to a frequency of 1.5 Hz. Higher frequencies caused significant changes in both renal haemodynamics and function.

Anesthesia↗
PubMed1998

The effect of electrical stimulation on colonic transit following spinal cord injury in cats.

The effect of direct electrical stimulation on colinic transit and manometric recordings following spinal cord injury were assessed in five adult male cats. Intra-colonic catheters were surgically placed, stimulating electrodes were sutured to the colonic serosa and a laminectomy with spinal cord clamping at a T4 level was done to induce spinal cord injury (SCI). Twenty radiopaque markers were inserted through an intra-colonic catheter located 1 cm distal to the cecum and were monitored with daily fluoroscopy as a measure of colonic transit. Transit measurements were compared before SCI, after SCI and after SCI with electrical stimulation of 40 pps, 1 ms, and 0-50 mA. Colonic transit following SCI was significantly prolonged (P<0.05) when compared to the transit before SCI. Electrical stimulation following SCI improved colonic transit to values not significantly different from those before SCI. Spontaneous colonic phasic motor activity was similar both before and after SCI. Manometric defection patterns were also observed to be similar before SCI and after SCI with electrical stimulation. Based on our scoring criteria, the most frequent response to electrical stimulation was an abdominal contraction. These findings demonstrate that colonic transit is prolonged following SCI and that direct electrical stimulation of the colon following SCI improves colonic transit in an animal model.

Animals↗
PubMed2006

Magnetic stimulation of the quadriceps femoris muscle: comparison of pain with electrical stimulation.

OBJECTIVE: The objective of this study was to compare pain induced by magnetic stimulation of the quadriceps femoris (QF) muscle with that induced by transcutaneous neuromuscular electrical stimulation (NMES). DESIGN: Magnetic stimulation and transcutaneous NMES were applied to QF muscles of 17 normal volunteers. The intensity of each mode of stimulation was increased in a stepwise manner. Peak torque values of isometric contractions of QF muscles and visual analog scale (VAS) scores were recorded at each intensity level. The VAS scores of the two stimulating modalities were compared at the intensity-generating same peak torque values. RESULTS: The median VAS scores for electrical and magnetic stimulation were 5.7 and 0.3, respectively. The median difference between the VAS scores for electrical and magnetic stimulation was 3.7 (range, 1.7-8.5). The mean of the maximum peak torque obtained from each subject was higher in magnetic stimulation than in electrical stimulation (9.5 +/- 4.8 vs. 4.4 +/- 2.9 Nm). CONCLUSIONS: Magnetic stimulation of the QF muscle produced less pain at the same level of isometric peak torque than did transcutaneous NMES. Magnetic stimulation is a potential alternative to transcutaneous NMES, especially for persons with intact or residual sensory function.

Adult↗
PubMed1993

Cerebral-evoked potential responses following direct vagal and esophageal electrical stimulation in humans.

Cerebral evoked responses following direct electrical stimulation of the vagus and esophagus were compared in 8 epileptic subjects and with those recorded after esophageal stimulation in 12 healthy nonepileptic controls. Direct vagal stimulation was performed using a left cervical vagal pacemaker, which is used in the treatment of epilepsy. Esophageal stimulation was obtained with the use of an esophageal assembly incorporating two electrodes positioned 5 and 20 cm orad to the lower esophageal sphincter. Evoked potential responses were recorded with the use of 20 scalp electrodes. The evoked potential responses consisted of three distinct negative peaks and were similar with the use of either vagal or esophageal stimulation. The measured conduction velocity of the afferent response was 7.5 m/s in epileptic subjects and 10 m/s in healthy controls, suggesting that afferent conduction is through A delta-fibers rather than slower C afferent fibers. We conclude that the cortical-evoked potential responses following esophageal electrical stimulation are comparable to direct electrical stimulation of the vagus nerve and involve mostly A delta-fibers. This approach provides a method for the assessment of vagal afferent gastrointestinal sensory pathways in health and disease.

Adult↗
PubMed2001

Quadriceps femoris muscle torques and fatigue generated by neuromuscular electrical stimulation with three different waveforms.

BACKGROUND AND PURPOSE: Neuromuscular electrical stimulation is used by physical therapists to improve muscle performance. Optimal forms of stimulation settings are yet to be determined, as are possible sex-related differences in responsiveness to electrical stimulation. The objectives of the study were: (1) to compare the ability of 3 different waveforms to generate isometric contractions of the quadriceps femoris muscles of individuals without known impairments, (2) to compare muscle fatigue caused by repeated contractions induced by these same waveforms, and (3) to examine the effect of sex on muscle force production and fatigue induced by electrical stimulation. SUBJECTS: Fifteen women and 15 men (mean age=29.5 years, SD=5.4, range=22-38) participated in the study. METHODS: A portable battery-operated stimulator was used to generate either a monophasic or biphasic rectangular waveform. A stimulator that was plugged into an electrical outlet was used to generate a 2,500-Hz alternating current. Phase duration, frequency, and on-off ratios were kept identical for both stimulators. Participants did not know the type of waveform being used. Torque was measured using a computerized dynamometer. A maximal voluntary isometric contraction (MVIC) of the right quadriceps femoris muscle set at 60 degrees of knee flexion was determined during the first session. In each of the 3 testing sessions, torque of contraction and fatigue elicited by one waveform were measured. Order of testing was randomized. Torque elicited by electrical stimulation was expressed as a percentage of average MVIC. A mixed-model analysis of variance was used to determine the effect of stimulation and sex on strength of contraction and fatigue. Bonferroni-corrected post hoc tests were used to further distinguish between the effects of the 3 stimulus waveforms. RESULTS: The results indicated that the monophasic and biphasic waveforms generated contractions with greater torque than the polyphasic waveform. These 2 waveforms also were less fatiguing. The torques from the maximally tolerated electrically elicited contractions were greater for the male subjects than for the female subjects. DISCUSSION AND CONCLUSION: Muscle torque and fatigue of electrically induced contractions depend on the waveform used to stimulate the contraction, with monophasic and biphasic waveforms having an advantage over the polyphasic waveform. All tested waveforms elicited, on average, stronger contractions in male subjects than in female subjects when measured as a percentage of MVIC.

Adult↗
PubMed2005

Simulation of intra-orbital optic nerve electrical stimulation.

In blind subjects who still have functional retinal ganglion cells, electrical stimuli applied to the optic nerve can produce localised visual sensations. This has been demonstrated with an intracranially implanted self-sizing spiral cuff electrode, but, to avoid skull opening, intra-orbital cuff implantation is now considered. In its orbital segment, the optic nerve is surrounded by subarachnoidal cerebrospinal fluid (CSF) and dura mater. Dura mater is a tough fibrous tissue that can impede electrical stimulation. In the study, the issue of whether or not to remove the dura mater at the implantation site was addressed using simulation on numerical models. Several volume conductor models were built representing, respectively: the cuff implanted directly around the nerve; the cuff over the nerve after connective tissue encapsulated the implant; and the cuff electrode placed around the dura mater. Stimulation-induced electric potential fields were computed for these configurations using a full 3D finite elements software. Responses of fibres within the nerve were computed. A large range of dural conductivities and several CSF thicknesses were considered. In all simulated conditions, the presence of dura mater around a layer of CSF increased excitation thresholds. Selectivity performance also decreased, but was found to be independent of the CSF thickness. However, simulations showed that, if the diameter of the cuff electrode is adapted to the target nerve, the injected charge associated with activation is limited within a reasonable range. Electrical stimulation of the optic nerve with a cuff electrode implanted around the dura mater should therefore be feasible.

Dura Mater↗
PubMedDate not supplied

A new method to generate canine seminal emission and its application to men: direct electrical stimulation of the vas deferens.

Seminal emission from the ejaculatory duct (SEED) by direct electrical stimulation of the vas deferens was investigated in the dog, and the technique was applied to men. The stimulus parameters used were 2 msec, 10 Hz, and 8 V for dogs or 15-20 V for humans. In vitro studies using tetrodotoxin demonstrated that the major portion of the muscle contraction under the above stimulation was neurogenic. The stimulation of the pars epididymica, the middle vas, or the ampulla of the vas caused SEED in all dogs having intact hypogastric nerves (HNs) and receiving transection of bilateral HNs 1, 6, and 12 months before electrical stimulation. The dye instilled into the canine cauda epididymis was transported to the ampulla and emitted into the posterior urethra by electrical stimulation of the vas regardless of the site stimulated. The electrical stimulation of eight vasa deferentia (pars epididymica) of five prostatic carcinoma patients generated emission from the severed proximal end of all vasa examined at orchidectomy. All of the stimulations of 13 middle vasa of seven patients with emission loss caused SEED. The above results indicate that direct electrical stimulation of the canine and human vas deferens causes SEED regardless of the site stimulated or the absence of HNs, which are the major pathway of the efferent signal for SEED.

Animals↗
PubMed1991

Electrical stimulation of peripheral and central pathways for the relief of musculoskeletal pain.

One method for the treatment of chronic musculoskeletal pain involves stimulation of the peripheral or central nervous system. Such stimulation includes transcutaneous electrical nerve stimulation, dorsal column stimulation, and deep brain stimulation. This review discusses the clinical use of electrical stimulation for the relief of musculoskeletal pain, and describes the results of studies conducted in our laboratory suggesting that such stimulation reduces pain transmission along sensory-discriminative pathways.

Animals↗
PubMed2005

Predicting optimal electrical stimulation for repetitive human muscle activation.

Functional electrical stimulation is the use of electrical currents to activate paralyzed muscles to produce functional movements. Muscle force output must meet or exceed the external load to maintain a posture or produce movements. A mathematical force-fatigue modeling system that predicts muscle force responses during repetitive electrical stimulation has been developed in our laboratory to help identify stimulation patterns that optimize force output for individual subjects. This study tests how well this model predicts the number of contractions that can be maintained above a required force level (successful contractions) during repetitive activation of a muscle. Healthy human quadriceps muscles were tested isometrically on 12 subjects. Data were first collected and used to parameterize the model. Next, the model was used to predict the number of successful contractions that were produced by trains with frequencies ranging from 5 to 100 Hz while the pulse durations and amplitudes were held constant. Finally, three clinically relevant stimulation frequencies were selected and tested to verify the model's predictions. Under these conditions, the model accurately predicted the number of successful contractions for clinically relevant stimulation frequencies. Furthermore, the model appears to have the potential to identify the stimulation frequency that maximizes muscle force output and minimizes fatigue for each subject.

Action Potentials↗
PubMed2003

Agonist contractions against electrically stimulated antagonists.

OBJECTIVE: To assess an exercise program that uses electrically stimulated antagonists to resist agonist muscle contractions. DESIGN: In 1 limb, electrically stimulated antagonists resisted elbow flexion and extension. In the other, stimulation occurred without volitional muscle contraction. SETTING: A biomechanics laboratory in Japan. PARTICIPANTS: Twelve men between the ages of 19 and 24 years. Subjects served as their own controls. INTERVENTION: Subjects trained 3 times a week for 12 weeks. Each session consisted of 10 sets of 10 elbow flexor and extensor contractions. MAIN OUTCOME MEASURES: Isokinetic elbow extension and flexion torques. Biceps and triceps brachii cross-sectional areas. RESULTS: Elbow extension torques increased (32.85% at 30 degrees/s, 27.20% at 60 degrees/s, 26.16% at 90 degrees/s; all P<or=.02) over the training period in limbs that trained against electrically stimulated antagonists. Control limb extension torque increases were smaller (8.52% -14.91%) and did not reach statistical significance. Elbow flexion torques improved in both groups, but the changes did not reach statistical significance. Cross-sectional areas increased in all muscles but were most marked in the antagonist stimulated limbs: triceps 16.20% versus 4.25% (P=.01) and biceps 16.65% versus 7.00% (P=.005). CONCLUSIONS: Exercises that use electrically stimulated antagonist muscles may be effective in increasing muscle strength and mass.

Adult↗