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At least 163 records · Page 9Linked to original sources
PubMed2005

Efficiency and efficacy of multi-channel gastric electrical stimulation.

Gastric electrical stimulation (GES) using single channel has been under investigation for its therapeutic potential for gastroparesis. The aim of this study was to study the efficacy and efficiency of multi-channel GES in accelerating gastric emptying in dogs. The study was performed in eight dogs, and gastric emptying of liquid was assessed in three randomized sessions of control, one-channel GES and four-channel GES. It was found that (i) GES of both one-channel and four-channel was able to completely entrain the slow waves in the entire stomach. However, the stimulation energy required by four-channel GES was only 1% of that required by one-channel GES. (ii) Four-channel, but not one-channel, GES significantly and substantially accelerated gastric emptying. An increase of 121.0 and 93.9% was noted with four-channel GES at 30 and 60 min after the meal, respectively. It was concluded that four-channel GES is substantially more efficient and effective than conventional single-channel GES in improving gastric emptying. It is worthy to explore its therapeutic potential for gastroparesis in clinical settings.

Animals↗
PubMed1984

Factors related to the induction of ventricular fibrillation in the normal canine heart by programmed electrical stimulation.

Programmed electrical stimulation was performed in eight normal dogs using a stimulator and endocardial electrode catheters identical to those used in human studies. The right and left ventricular apex were paced at a drive cycle length of 400 ms and, in some cases, 500 ms, with a pacing sequence of single (S1S2), double (S1S2S3) and triple (S1S2S3S4) premature impulses introduced after eight paced complexes. Pacing sequences were performed using combinations of pulse width (1, 2 and 4 ms) and current strengths of 2, 5 and 10 times diastolic threshold, and in three dogs, 15 times diastolic threshold. Twenty-two episodes of ventricular fibrillation were initiated in five dogs in 170 pacing sequences using current strengths up to 10 times diastolic threshold, and six episodes of ventricular fibrillation in the two of three remaining dogs tested at 15 times diastolic threshold. Ventricular fibrillation was reproducible on seven of nine occasions. Ventricular fibrillation was never induced by S1S2 at up to 15 times diastolic threshold; it was induced by S1S2S3 in 3 (1.8%) of 170 sequences, but only at 10 times diastolic threshold. It was induced by S1S2S3S4 in 19 (11.4%) of 167 sequences using 2 to 10 times diastolic threshold, although 20 of 28 episodes only occurred with S1S2S3S4 at 10 or more times diastolic threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A gated differential amplifier for recording physiological responses to electrical stimulation.

Artifact from electrical stimulation imposes a problem for the recording of physiological responses to electrical stimulation. Here we describe a simple, low-cost, gated differential amplifier for the recording of physiological responses to electrical stimulation. The gain of the amplifier is set to 1 during electrical stimulation by setting the gate input to a high logic state to avoid overloading of the amplifier by the artifact. Following electrical stimulation, the gate input is set to a low logic state, resulting in a gain of 1000 for frequencies between 300 Hz and 25 kHz (-3 dB points). The gain at low frequencies (0-0.2 Hz) is held constant at 1 to avoid transients in the output signal arising from changes in gain at these frequencies. The gain of the amplifier following stimulation (gate low) was independent of the magnitude of the artifact and was therefore suitable for the measurement of neural field potentials with low impedance electrodes.

Amplifiers, Electronic↗
PubMed1998

Microprocessor controlled movement of liquid gastric content using sequential neural electrical stimulation.

BACKGROUND: Gastric electrical stimulation has been attempted for several years with little success. AIMS: To determine whether movement of liquid gastric content could be achieved using microprocessor controlled sequential electrical stimulation. METHODS: Eight anaesthetised dogs underwent laparotomy and implantation of four sets of bipolar stainless steel wire electrodes. Each set consisted of two to six electrodes (10x0.25 mm, 3 cm apart) implanted circumferentially. The stomach was filled with water and the process of gastric emptying was monitored. Artificial contractions were produced using microprocessor controlled phase locked bipolar four second trains of 50 Hz, 14 V (peak to peak) rectangular voltage. In four of the dogs four force transducers were implanted close to each circumferential electrode set. In one gastroparetic patient the effect of direct electrical stimulation was determined at laparotomy. RESULTS: Using the above stimulating parameters circumferential gastric contractions were produced which were artificially propagated distally by phase locking the stimulating voltage. Averaged stimulated gastric emptying times were significantly shorter than spontaneus emptying times (t1/2 6.7 (3.0) versus 25.3 (12.9) minutes, p<0.01). Gastric electrical stimulation of the gastroparetic patient at operation produced circumferential contractions. CONCLUSIONS: Microprocessor controlled electrical stimulation produced artificial peristalsis and notably accelerated the movement of liquid gastric content.

Animals↗
PubMed1991

Effect of adenosine on 45Ca2+ uptake by electrically stimulated rat brain synaptosomes.

The effect of adenosine on 45Ca2+ uptake by rat brain synaptosomes stimulated by electrical pulses was investigated. 45Ca2+ uptake was voltage dependent. Adenosine (1 nM-1 microM) decreased the uptake of 45Ca2+ induced by electrical stimulation (amplitude, 20 V; duration, 400 microseconds; frequency, 10 pulses/s) in a concentration-dependent manner. At a concentration of 1 microM, adenosine almost abolished the 45Ca2+ uptake induced by electrical stimulation (92.9 +/- 5.3% inhibition), but when the calcium uptake was induced by high-K+ (60 mM) medium, the effect of adenosine (1 microM) was smaller (43.8 +/- 5.2% inhibition). The inhibitory effect of 1 microM adenosine on calcium uptake induced by electrical stimulation was antagonized by 1,3-dipropyl-8-p-sulfophenylxanthine (5 microM). The possibility that adenosine interacts with the calcium channels opened by electrical stimulation is discussed.

Adenosine↗
PubMed2005

Colon emptying induced by sequential electrical stimulation in rats.

Electrical stimulation could be used to induce colon emptying. The present experiments were performed to establish a stimulation pattern to optimize the stimulation parameters and to test neural involvement in propulsion induced by electrical stimulation. Colon segments were sequentially stimulated using rectangular pulses. The resulting propulsive activity displaced intraluminal content in consecutive propulsion steps. The propulsion steps differed in displacement latency, distance, and velocity along the stimulated colon. Increasing the pulse duration or amplitude resulted in a decrease of the latency. Increasing the stimulation amplitude doubled the displacement distance. The frequencies tested in the present study did not affect propulsion. Inhibition of cholinergic and nitrergic pathways inhibited propulsion. Electrical stimulation can induce colonic propulsion. Motor differences are present along the descending colon. The most suitable combination of pulse parameters regarding colon stimulation is 0.3 ms, 5 mA, 10 Hz. Neural circuits are involved in propulsion when using these values.

Animals↗
PubMed2003

[Intercavitary electrical stimulation of the gastrointestinal tract and mucosa with a stand-alone electric stimulator in the treatment of patients in the physicochemical stage of gallbladder disease].

The use of the SAE for the GIT and MC has a stimulating effect on the processes of bile production and secretion for patients with the physical and chemical stage of the gallstone disease. Over a short period of time the SAE for the GIT and MC normalizes the biliary tract motor functions removing the dissynergism of the biliary tract sphincter organ and restoring the sphincter motor functions. The SAE for the GIT and MC has a positive effect on major factors of bile concentration and components ratio aimed at the reduction of lithogenicity and its colloid stability improvement. The intracavitary electrical stimulation with the SAE for the GIT and MC both as a monotherapy and one of the complex anti-relapse methods is an efficient and simple method and has no side effects or complications. Therefore, it may be recommended for the treatment of patients with the physical and chemical stage of the gallstone disease.

Bile↗
PubMed2006

Stimulation parameter optimization for functional electrical stimulation assisted gait in human spinal cord injury using response surface methodology.

BACKGROUND: The aims of this study were to identify the reflex moment induced by flexion withdrawal reflex and to optimize stimulation parameters for restoring swing motion with respect to initial kinematic conditions in human with spinal cord injury. METHODS: The influence of hip position and passive movement in the reflex moment were tested in six subjects with chronic spinal cord injury. The two-dimensional dynamic models consisted of thigh, shank and foot segments were developed to compute the swing-phase response and the response surface method was also used to optimize stimulation parameters for restoration of gait by functional electrical stimulation. FINDINGS: At three different hip positions, significant linear relationship was found between the reflex moment and hip angle (P < 0.05) and hip movement also increased the reflex moment compare to isometric conditions. The hip and knee flexion velocities significantly contributed to the hip and knee flexion angle during the swing-phase (P < 0.05) and increase of initial joint velocity resulted in a decrease of the burst frequency and duration time for optimal swing motion in spinal cord injured patients. INTERPRETATION: From dynamic simulation, we concluded that optimal solutions of pulse amplitude, frequency and duration time of burst for electrical stimulation assisted gait were influenced by initial kinematic conditions at toe-off. The reflex model and the results of this study can be applied to the design and control strategies of neuroprosthetic devices using functional electrical stimulation for spinal cord injured patients.

Adult↗
PubMed2005

Brain stimulation and conscious experience: electrical stimulation of the cortical surface at a threshold current evokes sustained neuronal activity only after a prolonged latency.

Libet demonstrated that a substantial duration (>0.5-1.0 s) of direct electrical stimulation of the surface of a sensory cortex at a threshold or liminal current is required before a subject can experience a percept. Libet and his co-workers originally proposed that the result could be due either to spatial and temporal facilitation of the underlying neurons or additionally to a prolonged central processing time. However, over the next four decades, Libet chose to attribute the prolonged latency for evoking conscious experience to a prolonged central processing time. In my view, Libet has not provided any convincing evidence, either on the basis of his own past work or in his critique of my paper, for his hypothesis of a central processing time exceeding 0.5s before conscious experience emerges following direct electrical threshold stimulation of the cortical surface. I stand by my original results and conclusion that such prolonged latencies are largely the consequence of a dynamically increasing cortical facilitatory process that begins hundreds of milliseconds before there is a sustained neuronal activation. In some cases, the facilitatory process must overcome an initial stimulus-induced inhibition before neuronal firing commences.

Consciousness↗
PubMed2002

Development of an EMG recording device from stimulation electrodes for functional electrical stimulation.

A device that records voluntary EMG from a pair of surface stimulation electrodes has been developed for functional electrical stimulation (FES). The device can apply to a small muscle on which it is difficult to locate both the stimulation electrodes and recording electrodes. The device utilizes photo-MOS relays to disconnect the stimulator when it is not active, to ground the electrodes after delivering the stimulation pulses, and to drop the gain of the EMG amplifier during the stimulus period. The device is able to detect the voluntary EMG of a small muscle from the stimulation electrodes for the EMG-controlled FES system.

Adult↗
PubMed1987

Relaxation of canine coronary artery to electrical stimulation: limited role of free radicals.

Electrical stimulation induces tetrodotoxin-insensitive relaxation of the canine coronary artery. The present study was designed to verify whether this relaxation involves the production of oxygen-derived free radicals. Isolated rings of canine coronary arteries were suspended for isometric tension recording in organ chambers filled with Krebs-Ringer bicarbonate solution. They were stimulated electrically (9 V, 3 Hz, 2 ms for 2 min) by means of two platinum electrodes during contractions evoked by various vasoactive agonists. Under control conditions, electrical stimulation caused rapid, reversible relaxations. Superoxide dismutase in association with catalase or mannitol, sodium ascorbate, dimethyl sulfoxide, and glutathione did not inhibit the relaxation caused by stimulation applied for only 2 min; neither did the removal of chloride ions from the salt solution nor the association of Cl-free solution in the presence of mannitol, superoxide dismutase, and catalase. Prolonging the electrical stimulation (9 V, 3 Hz, 2 ms) for up to 20 min produced a secondary relaxation. This second phase was inhibited by sodium ascorbate. These experiments indicate that the rapid relaxation induced by short-lasting electrical stimulation is probably not due to the generation of oxygen-derived free radicals. However, prolonged stimulation causes the production of such radicals, which then evoke irreversible inhibition of the vascular smooth muscle of the canine coronary artery.

Animals↗
PubMed2003

Increased c-Fos expression in select lateral parabrachial subnuclei following chemical versus electrical stimulation of the dorsal periaqueductal gray in rats.

The parabrachial nucleus (PBN) is located in the rostral dorsolateral pons and has been identified as a critical relay for cardiovascular responses (sympathoexcitation and baroreflex attenuation) evoked by the dorsal periaqueductal gray (PAG). We examined the pattern of c-Fos protein immunoreactivity throughout the rostral-caudal extent of the PBN in four groups of anesthetized male Sprague-Dawley rats to identify the specific PBN regions activated by dorsal PAG stimulation. Both electrical stimulation and chemical (0.3 mM bicuculline methobromide) activation of the dorsal PAG elicited a selective increase in Fos-like immunoreactivity (FLI) in the superior lateral and central lateral subnuclei of the rostral lateral PBN (LPBN) relative to surgery and blood pressure control groups. In the middle LPBN chemical stimulation of the dorsal PAG selectively increased FLI in the central lateral subnucleus while electrical stimulation increased FLI in the Kolliker-Fuse area only. Finally, in the caudal LPBN only electrical stimulation of the dorsal PAG induced significant changes in FLI above control. Significant changes in FLI in the medial PBN were not observed under any experimental conditions. These results confirm neuroanatomical data demonstrating that neurons in superior lateral and central lateral subnuclei of the rostral and middle LPBN are the primary targets of the dorsal PAG. Our results also demonstrate that this descending projection to the central lateral and superior lateral subnuclei of the LPBN is in part excitatory. Finally, our results raise the possibility that neurons in the central lateral subnucleus of the middle and rostral LPBN are integrally involved in descending modulation of sympathetic drive associated with dorsal PAG activation.

Animals↗
PubMed1981

Somatosensory evoked potentials elicited by mechanical and electrical stimulation of each single pain or tactile spot of the skin.

Single pain and tactile spots on the dorsum of the right hand in man were stimulated by electric pulses and mechanical taps using a needle to a pain spot and a horse tail bristle to a tactile one. Somatosensory evoked potentials (SEPs) and far field potentials (FFPs) were observed in three volunteers by averaging of 200 or 400 samples of responses recorded from scalp points corresponding to the left and right somatosensory areas (LSA and RSA). For SEP measurements, the difference between responses at LSA and RSA was obtained in order to specify the optimum response at LSA. The patterns of SEPs elicited by mechanical or electrical stimulation to a pain spot were similar to those to a tactile one. The typical SEP to mechanical stimulation consisted of N23, P31, N40, P49, N64, P87, N114 and P147, while that to electrical stimulation did of N24, P33, N42, P52, N66, P95, N122 and P156. Consequently, mean peak latencies of the later components in SEPs elicited by mechanical stimulation were earlier than those to electrical one. The SEP amplitudes for mechanical stimulation were 1-3 microV and were larger than those to electrical one. By mechanical stimulation FFPs could not be obtained, while by electrical stimulation FFPs in peak latency of approximately 14 msec (P14) were seen. No specific components to sensory modality of pain or tactile sensation were observed either in SEPs or in FFPs.

Adult↗
PubMed1977

Dissociation of hippocampal EEG from its behavioral correlates by septal and hippocampal electrical stimulation.

(1) Electrical stimulation of septum or hippocampus produced frequency specific hippocampal synchrony and hippocampal desynchrony. (2) Behaviors normally correlated with the occurrence of hippocampal desynchrony continued during elicitation of synchrony. Similarly, behaviors normally correlated with the occurrence of synchrony continued during elicitation of desynchrony. Stated conversely, specific hippocampal patterns were elicited without eliciting the behaviors which occur when similar patterns are generated by the spontaneously behaving animal. (3) These results suggest that the import of hippocampal patterns highly correlated with specific types of behaviors might best be sought in processes remote from the endpoint of motor performance per se.

Animals↗