Noninvasive method to control the human spinal locomotor systems

The mechanism of interactions between receptor activation in the musculoskeletal system and stimulation of the spinal cord in the regulation of locomotor behavior was studied in healthy subjects. Afferent stimulation was tested for effect on the patterns of stepping movements induced by percutaneous stimulation of the spinal cord. A combination of percutaneous spinal cord stimulation and vibratory stimulation was shown to increase the amplitude of leg movements. It was demonstrated that vibratory stimulation of limb muscles at a frequency of less than 30 Hz can be used to control involuntary movements elicited by noninvasive stimulation of the spinal cord.     

Relative contribution of neurotransmission failure to diaphragm fatigue

Two procedures were used to estimate the relative contribution of neurotransmission failure (NF) to fatigue of the rat diaphragm at different rates of phrenic nerve stimulation. In one, direct muscle stimulation was intermittently superimposed on neural stimulation of the diaphragm, and the relative contribution of NF was estimated by the difference in generated tension. In a second procedure, diaphragm fatigue was induced by using either direct muscle stimulation (with complete blockade of the neuromuscular junction by d-tubocurare) or phrenic nerve stimulation. The relative contribution of NF to diaphragm fatigue was then estimated by comparing the force loss during these two modes of stimulation. With both procedures, it was observed that 1) the relative contribution of NF to diaphragm fatigue was less than 45% at each frequency of phrenic nerve stimulation; 2) the relative contribution of NF to diaphragm fatigue increased at higher rates of phrenic stimulation, reaching a maximum at 75 pulses/s; and 3) the relative contribution of NF to diaphragm fatigue reached a plateau after 2 min of repetitive stimulation.     

Is maximum stimulation intensity required in the assessment of muscle activation capacity?

Voluntary activation assessment using the interpolation twitch technique (ITT) has almost invariably been done using maximal stimulation intensity, i.e., an intensity beyond which no additional joint moment or external force is produced by increasing further the intensity of stimulation. The aim of the study was to identify the minimum stimulation intensity at which percutaneous ITT yields valid results. Maximal stimulation intensity and the force produced at that intensity were identified for the quadriceps muscle using percutaneous electrodes in eight active men. The stimulation intensities producing 10–90% (in 10% increments) of that force were determined and subsequently applied during isometric contractions at 90% of maximum voluntary contraction (MVC) via twitch doublets. Muscle activation was calculated with the ITT and pain scores were obtained for each stimulation intensity and compared to the respective values at maximum stimulation intensity. Muscle activation at maximal stimulation intensity was 91.6 (2.5)%. The lowest stimulation intensity yielding comparable muscle activation results to maximal stimulation was 50% (88.8 (3.9)%, p < 0.05). Pain score at maximal stimulation intensity was 6.6 (1.5) cm and it was significantly reduced at 60% stimulation intensity (3.7 (1.5) cm, p < 0.05) compared to maximal stimulation intensity. Submaximal stimulation can produce valid ITT results while reducing the discomfort obtained by the subjects, widening the assessment of ITT to situations where discomfort may otherwise impede maximal electrostimulation.     

Mechanically induced avoidance response of chloroplasts in fern protonemal cells.

Cell response to mechanical stimulation was investigated at a subcellular level in protonemal cells of the fern Adiantum capillus-veneris L. by pressing a small part of the cell with a microcapillary. In cells receiving local stimulation, the chloroplasts moved away from the site of stimulation, whereas the nuclei failed to show such avoidance movement. Mechanical stimulation for a period as short as 0.3 min was enough to induce the avoidance response to a maximal level. The avoidance movement of chloroplasts started within 30 min and the plateau level of avoidance was attained around 2 h after stimulation. By tracing the movement of chloroplasts during the response, it was shown that the mobility of chloroplasts near the stimulation site increased transiently within 1 h after the stimulation. After 2 to 3 h, it slowed down to the control level without stimulation. The avoidance response was inhibited by 0.1 mM cytochalasin B and 25 mM 2, 3-butanedione monoxime but not by 3.3 microM amiprophosmethyl or 5 mM colchicine. These findings indicate that the protonemal cells were very sensitive to mechanical stimulation and that chloroplasts moved away from the mechanically stimulated site through the actomyosin motile system.     

蓝斑核调制电刺激包钦格复合体引起的吸气抑制效应

实验选用成年健康家兔,用乌拉坦麻醉,以膈神经放电为指标,观察了电刺激和化学刺激脑桥蓝斑核对延髓包钦格复合体吸气抑制效应的影响。结果观察到:(1)长串电刺激蓝斑核后,在一定时间之内电刺激包钦格复合体所导致的膈神经放电抑制效应明显减弱,与对照组(仅刺激包钦格复合体)相比,抑制程度减弱(28.78 ±19.49)%。(2)蓝斑核内微量注射谷氨酸钠后,电刺激包钦格复合体导致的膈神经放电抑制效应明显减弱,与对照组相比,抑制程度减弱(19.18 ±8.06)%,与长串电刺激蓝斑核的效应一致。这些结果提示,蓝斑核对包钦格复合体吸气抑制效应具有调制作用。     

躯体传入冲动抑制中枢性心肌缺血的脊髓机制

本工作在58只尿酯-氯醛糖麻醉,三碘季铵酚制动,人工呼吸,切断迷走神经的兔上进行。结果显示:电刺激正中神经(MN)和腓深神经(DPN)均能抑制或部分抑制下丘脑背内侧核(DMH)诱发的缺血性心电 ST 段偏移,以刺激 MN 的抑制作用更为明显。蛛网膜下腔注射(ith)吗啡(40μg)也能抑制这种缺血性心电变化。ith 纳洛酮(20μg)则可阻断刺激 MN 对中枢性心肌缺血的抑制作用。完整兔在刺激左侧 MN 或 DPN 后,用放射免疫技术测得胸 2—5(T_2-5)节段两侧中间外侧柱(IML)中亮氨酸脑啡肽(LENK)含量明显增加。在颈1(C_1)水平横断脊髓,以同样参数刺激左侧 MN,同侧胸髓 IML 中 LENK 含量明显增加,而对侧胸髓 IML 中 LENK 含量无明显改变;刺激一侧 DPN,T_(2-5)的两侧 IML 中 LENK 含量均无明显变化。上述结果表明,刺激 MN 与 DPN 均能抑制 DMH 诱发的中枢性心肌缺血,但以MN 作用较明显。我们推测这种抑制作用可能与通过脊上机制双侧性增加 IML 中 LENK 含量有关,MN 的抑制作用可能尚包括直接激活胸髓内的脑啡肽系统,增加同侧 IML 中 LENK含量,加强了对交感输出活动的抑制作用。     

Maps of somatosensory evoked potentials (SEPs) to mechanical (tapping) stimuli: comparison with P14, N20, P22, N30 of electrically elicited SEPs

Bit mapped color imaging of SEPs was recorded from 19 derivations in 11 healthy volunteers after electrical stimulation of the median nerve at the wrist, index finger digital nerve stimulation, and mechanical stimulation of the index fingertips by an electromechanically driven vibrating thin metallic plate. The latencies of SEP components increased for the various stimulation modalities, being shortestafter median nerve stimulation at the wrist and longest after mechanical stimulation of the index fingertips.The scalp distribution of SEPs to mechanical stimuli was, however, the same as other SEPs, independently of the stimulation employed, and components corresponding to N20 and P22 were recorded only contralaterally to the stimulated side.     

Neurophysiological analysis of efferent-afferent interaction of neurons of the parietal associate cortex in cats

Neuronal responses of the parietal associate cortex (field 5) was recorded in waking cat during electrical stimulation of the pyramidal tract axons and afferent stimulation. The electrical stimulation of the pyramid evoked marked responses in 39% of neurons. 87% of these neurons increased spike activity during sematic nociceptive stimulation, 61% of test neurons were activated by light or tonal stimulation. Neuronal activity was recorded during defensive conditioning to the pyramidal tract axons stimulation. It has been shown that conditioned stimulation of the pyramidal tract evoked plastic changes of responses in 66% of neurons of the parietal cortex. These data are discussed relative to the possible functional role of the efferent-afferent interaction to field 5.     

Unit responses of the cat somatosensory cortex to stimulation of the reticular and anteroventral thalamic nuclei

Responses of 189 neurons of the somatosensory cortex to stimulation of the nonspecific reticular (R) and anteroventral (AV) nuclei of the thalamus were studied in cats anesthetized with thiopental and immobilized with tubocurarine. In the series of experiments with stimulation of R and, for comparison, of the specific ventral posterolateral nucleus (VPL), 132 neurons were recorded, of which 22 (16.7%) did not respond to stimulation of these nuclei, 77 (58.3%) responded only to stimulation of VPL, and 33 (25%) responded to stimulation of both VPL and R. In the series of experiments in which AV was stimulated, 57 neurons were recorded. Eight (14.8%) responded to neither stimulus and 25 (43.1%) responded only to stimulation of VPL; 24 responded to stimulation of AV (42.1%), and of these, 10 also responded to stimulation of VPL. A characteristic feature of unit responses in the somatosensory cortex to stimulation of the nonspecific nuclei was the irregularity of the responses and their longer latent period. Only five cells responded sooner to stimulation of the nonspecific nuclei than to stimulation of VPL. Responses of the nonspecific nuclei to stimulation appeared clearly only if the stimulation was repetitive. Preliminary stimulation of R blocks the response to stimulation of VPL during the subsequent 40–60 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol.4, No.4, pp. 384–390, July–August, 1972.     

The Effects of Alpha (10-Hz) and Beta (22-Hz) “Entrainment” Stimulation on the Alpha and Beta EEG Bands: Individual Differences Are Critical to Prediction of Effects

Two different groups of normal college students were formed: One (the alpha group) received 10-Hz audiovisual (AV) stimulation for 8 minutes, and the other (beta) group received 22-Hz AV stimulation for 8 minutes. EEG power in the alpha (8-13 Hz) and beta (13-30 Hz) bands was FFT-extracted before, during, and for 24 minutes after stimulation. It was found that baseline (prestimulation) alpha and beta power predict the effects of stimulation, leading to individual differences in responsivity. High-baseline alpha participants showed either no entrainment or relatively prolonged entrainment with alpha stimulation. Low-baseline participants showed transient entrainment. Baseline alpha also predicted the direction of change in alpha with beta stimulation. Baseline beta and alpha predicted beta band response to beta stimulation, which was transient enhancement in some participants, inhibition in others. Some participants showed relatively prolonged beta enhancement with beta stimulation.     

Blockage of induced pseudopregnancy by electrochemical stimulation of the limbic system.

Pseudopregnancy induced by cervical stimulation was inhibited by acute electrochemical stimulation of the corticomedial amygdala or dorsal hippocampus under sodium pentobarbital anesthesia (40 mg/kg) in adult, cyclic female Sprague-Dawley rats. The degree to which pseudopregnancy was blocked depended on temporal conditions of brain stimulation and sodium pentobarbital administration. Pentobarbital alone had a suppressing effect on the incidence of pseudopregnancy, especially when it preceded cervical stimulation. Limbic stimulation before cervical stimulation had a tendency to potentiate the suppression of pseudopregnancy by pentobarbital. After cervical stimulation, hippocampal stimulation tended to inhibit the development of pseudopregnancy, potentiating the pentobarbital suppression, while amygdala stimulation tended to override the pentobarbital blockage of pseudopregnancy. These findings suggest a negative influence of these two limbic structures and pentobarbital on the secretion of prolactin.     

Ovarian blood flow responses to electroacupuncture stimulation depend on estrous cycle and on site and frequency of stimulation in anesthetized rats.

Electroacupuncture (EA) applied to the abdomen and hindlimb modulates the ovarian blood flow (OBF) response. The present study aimed to further elucidate the role of the site and the frequency of short-term EA stimulation and the influence of the estrous cycle on the OBF response using anesthetized rats. EA stimulation was applied to the abdominal or the hindlimb muscles at three different frequencies (2, 10, and 80 Hz) during the estrus or diestrus phase. Involvement of spinal and supraspinal reflexes in OBF responses to EA stimulation was investigated by spinal cord transection. Abdominal EA stimulation at 10 Hz increased the OBF response, whereas hindlimb EA stimulation at 10 Hz and abdominal and hindlimb stimulation at 80 Hz decreased the OBF response; 2-Hz EA caused no OBF response. The OBF response to abdominal EA was more pronounced in the estrus than the diestrus phase. The OBF response to abdominal and hindlimb EA stimulation at both 10 and 80 Hz was almost abolished, both after severance of the sympathetic nerves and after spinal cord transection. In conclusion, the OBF response to both abdominal and hindlimb EA stimulation was mediated as a reflex response via the ovarian sympathetic nerves, and the response was controlled via supraspinal pathways. Furthermore, the OBF response to segmental abdominal EA stimulation was frequency dependent and amplified in the estrous phase.     

Fatigue of isolated rat diaphragm: role of impaired neuromuscular transmission

We compared the contributions of impaired neuromuscular transmission (transmission fatigue) and impaired muscle contractility (contractile fatigue) to fatigue of the isolated rat diaphragm. To make this comparison, we measured the differences in active tension elicited by direct muscle stimulation and by indirect (phrenic nerve) stimulation before and after fatigue induced by indirect supramaximal stimulation at varying frequencies and durations. Transmission fatigue was observed after all experimental protocols. Although significant contractile fatigue was not demonstrated after brief periods of low-frequency stimulation (6 min, 15 Hz, 25% duty cycle), it was present after longer or higher frequency stimulation. We repeated the direct stimulation in the presence of neuromuscular blockade with 6 microM d-tubocurarine to demonstrate that a reduced response to stimulation of intramuscular branches of the phrenic nerve during direct stimulation was not responsible for the apparent contractile fatigue. Since we found significant decreases in the response to direct stimulation even after neuromuscular blockade, we could verify the presence of contractile fatigue. We conclude that both contractile and transmission fatigue can occur in the isolated rat diaphragm and that transmission fatigue is a much more important factor after brief periods of fatiguing contractions.     

Convergence of antennal and ocellar inputs in the insect brain

Summary Unitary responses were recorded from the brain of the fleshfly, Boettcherisca peregrina, during olfactory or mechanical stimulation of the antenna, and simultaneous photic stimulation of the ocelli. Convergence from the two inputs, the antenna and the ocelli, was observed. The response to antennal stimulation was facilitated by photic stimulation in most units. The responses to the antennal stimuli were facilitated greatly at the peak of the photic response. Some units responded both to ocellar illumination and antennal stimulation. Their response to antennal stimulation seemed independent of the light-condition during the light-adapted state, but was facilitated at the onset of the ocellar illumination, and occluded just after its cessation. In addition, there were some units which responded to antennal stimulation but not to the ocellar illumination; some of them also showed facilitation of the response to antennal stimulation during ocellar illumination.     

Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation.

Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered to triceps surae and wrist flexors (muscle stimulation) and to median and tibial nerves (nerve stimulation) at two intensities. Contractions were evaluated for amplitude, consistency, and stability. Surface electromyograph was collected to assess how H-reflexes and M-waves contribute. In the triceps surae, muscle stimulation produced the largest absolute contractions (23% maximal voluntary contraction), evoked the largest extra contractions as torque increased by 412% after the 100-Hz stimulation, and was more consistent and stable compared with tibial nerve stimulation. Absolute and extra contraction amplitude, consistency, and stability of evoked wrist flexor torques were similar between stimulation types: torques reached 11% maximal voluntary contraction, and extra contractions increased torque by 161%. Extra contractions were 10 times larger in plantar flexors compared with wrist flexors with muscle stimulation but were similar with nerve stimulation. For triceps surae, H reflexes were 3.4 times larger than M waves during nerve stimulation, yet M waves were 15 times larger than H reflexes during muscle stimulation. M waves in the wrist flexors were larger than H reflexes during nerve (8.5 times) and muscle (18.5 times) stimulation. This is an initial step toward utilizing extra contractions for neuromuscular electrical stimulation and the first to demonstrate their presence in the wrist flexors.     

Distribution of lumbar spinal evoked potentials and their correlation with stimulation-induced paresthesiae

In 7 awake patients with neuropathic lower extremity pain, spinal somatosensory evoked potentials (SEP) were elicited from the non-painful leg by electrical stimulation of the peroneal nerve and mechanical stimulation of the hallux ball. Recording was made epidurally in the thoraco-lumbar region by means of an electrode temporarily inserted for trial of pain-suppressing stimulation.In response to peroneal nerve stimulation, two major SEP complexes were found. The first complex consisted, as has been described earlier, of an initial positivity (P12), a spike-like negativity (N14), a slow negativity (N16) and a slow positivity (P23). The second complex consisted of a slow biphasic wave, conceivably mediated by a supraspinal loop. Both complexes had a similar longitudinal distribution with amplitude maxima at the T12 vertebral body.The SEP evoked by mechanical hallux ball stimulation had a relatively small amplitude, and there was no significant second complex. The relationship between stimulus intensity and SEP amplitude was negatively accelerating.The longitudinal distribution of spinal SEP was compated with the somatotopic distribution of paresthesiae induced by stimulation through the epidural electrode. It was found that stimulation applied at the level of maximal SEP generally induced paresthesiae in the corresponding peripheral region. Therefore, spinal SEP may be used as a guide for optimal positioning of a spinal electrode for therapeutic stimulation when implanted under general anesthesia.An attempt was made to record the antidromic potential in the peroneal nerve elicited from the dorsal columns by epidural stimulation. The antidromic response was, however, very sensitive to minimal changes of stimulus strength and body position of the patient, and was also contaminated by simultaneously evoked muscular reflex potentials.Thus, peripheral responses evoked by epidural stimulation appeared too unreliable to be useful for the permanent implantation of a spinal electrode for therapeutic stimulation.     

Trace rhythm recruitment by the neurons of the rabbit sensorimotor cortex in old age]

Spectral analysis (ACG and gSP) of the impulse activity of the neurones of the old rabbits sensorimotor cortex allowed to reveal a trace recruitment of the rhythm--CR analogue to time--in after-action f rhythmic stimulation. Connection was established between the number of presented series of periodic electrocutaneous stimulation and expressiveness of the trace rhythm recruitment depending on the animals age. Trace rhythm recruitment took place slower in old animals (54-56 months) than in young ones (up to 1 year), chiefly in 2-3 experimental days after 2-4 series of rhythmic stimulation and was preserved in a small percent of cases the next day after stimulation. In the background activity of a number of neurones an initial periodicity was discovered, which was intensified under the influence of stimulation by another frequency, or the initial rhythm was extinguished, and stimulation rhythm was reproduced. Periodical stimulation in very old animals (66-85 months) practically did not evoke plastic reconstructions of the cortical neurones. Under the influence of the stimulation a non-specific trace increase of the frequency of neurones background activity of the old animals was observed. The revealed characteristics of plastic neurones properties may testify to projected disturbances of mnestic processes at definite age stages of normal aging.     

Prolonged poststimulation inhibition of bladder activity induced by tibial nerve stimulation in cats

Inhibition of bladder activity by tibial nerve stimulation was investigated in α-chloralose-anesthetized cats with an intact spinal cord. Short-duration (3-5 min) tibial nerve stimulation at both low (5 Hz) and high (30 Hz) frequencies applied repeatedly during rhythmic isovolumetric bladder contractions was effective in inhibiting reflex bladder activity. Both frequencies of stimulation were also effective in inducing inhibition that persisted after the termination of the stimulation. The poststimulation inhibitory effect induced by the short-duration stimulation significantly increased bladder capacity to 181.6 ± 24.36% of the control capacity measured before applying the stimulation. Thirty-minute continuous stimulation induced prolonged poststimulation inhibition of bladder activity, which lasted for more than 2 h and significantly increased bladder capacity to 161.1 ± 2.9% of the control capacity. During the poststimulation periods, 5-Hz stimulation applied during the cystometrogram elicited a further increase (~30% on average) in bladder capacity, but 30-Hz stimulation was ineffective. These results in cats support the clinical observation that tibial nerve neuromodulation induces a long-lasting poststimulation inhibitory effect that is useful in treating overactive bladder symptoms.     

室旁核在刺激肾神经传入纤维对血浆皮质醇浓度影响中的作用

本文在氯醛糖麻醉猫中探讨室旁核毁损前、后,电刺激肾神经传入纤维对血浆皮质醇浓度的影响。在动脉压力感受器完整猫中,刺激肾神经传入纤维对血浆皮质醇浓度无明显影响,但在动脉压力感受器去神经和迷走神经切断(SAD+VD)后,电刺激肾神经中枢端引起血浆皮质醇浓度升高。微量注射红藻氨酸毁损双侧室旁核后,可阻断刺激肾神经传入纤维引起的血浆皮质醇浓度升高,这些结果表明:动脉压力感受性反射可抑制刺激猫肾神经传入纤维引起的血浆皮质醇浓度升高;室旁核在刺激肾神经传入纤维引起的血浆皮质醇浓度升高效应中起重要作用。