Stimulation Rate Research Articles

Assessing subclinical hearing loss in musicians and nonmusicians using auditory brainstem responses and speech perception measures

In this study, the physiological and perceptual correlates of auditory function in student musicians and nonmusicians with normal hearing thresholds were investigated. The measures involved were auditory brainstem responses as a function of stimulation rate, spatial release from masking, and word intensity rollover functions. The results indicated that as the stimulation rate was increased, the wave I amplitude reductions were more abrupt in musicians than in nonmusicians. However, no significant group differences were observed for speech tasks. There were also no significant correlations between the results of speech perception and the measures of peripheral neural function.

Evaluation of Olfactory Thresholds in Patients of Allergic Rhinitis: Pre and Post Intranasal Steroid Therapy

characterized by one or more symptoms, including sneezing,itching, nasal congestion and rhinorrhoea along with usualsymptoms, and there is generally a decrease in the nasal airflowtherefore decrease in nasal air exchange, thereby decreasingthe rate of olfactory nerve ending stimulation hence decreasingthe perception of smell. We assessed the olfactory thresholdsin patients of allergic rhinitis using n-butanol solutions and theimpact of intranasal fluticasone furoate therapy on olfaction.Materials and methods: One hundred fifty patients withallergic rhinitis in the age group of 18 to 65 years were included.A total of 150 people from the general population as controls.In 6 weeks of fluticasone furoate nasal spray was administeredfor 6 weeks and olfactory threshold changes were observedat the end.Results: A significant change in n-butanol olfaction levels aftersteroid therapy was observed (p-value < 0.05).Conclusion: Intranasal steroid therapy shows remarkablebenefit in the improvement of allergic rhinitis and therebyimproving olfaction.

Effects of the Number of Channels and Channel Stimulation Rate on Speech Recognition and Sound Quality Using Precurved Electrode Arrays.

This study investigated the relationship between the number of active electrodes, channel stimulation rate, and their interaction on speech recognition and sound quality measures while controlling for electrode placement. Cochlear implant (CI) recipients with precurved electrode arrays placed entirely within scala tympani and closer to the modiolus were hypothesized to be able to utilize more channels and possibly higher stimulation rates to achieve better speech recognition performance and sound quality ratings than recipients in previous studies. Participants included seven postlingually deafened adult CI recipients with Advanced Bionics Mid-Scala electrode arrays confirmed to be entirely within scala tympani using postoperative computerized tomography. Twelve conditions were tested using four, eight, 12, and 16 electrodes and channel stimulation rates of 600 pulse per second (pps), 1,200 pps, and each participant's maximum allowable rate (1,245-4,800 pps). Measures of speech recognition and sound quality were acutely assessed. For the effect of channels, results showed no significant improvements beyond eight channels for all measures. For the effect of channel stimulation rate, results showed no significant improvements with higher rates, suggesting that 600 pps was sufficient for maximum speech recognition performance and sound quality ratings. However, across all conditions, there was a significant relationship between mean electrode-to-modiolus distance and all measures, suggesting that a lower mean electrode-to-modiolus distance was correlated with higher speech recognition scores and sound quality ratings. These findings suggest that even well-placed precurved electrode array recipients may not be able to take advantage of more than eight channels or higher channel stimulation rates (> 600 pps), but that closer electrode array placement to the modiolus correlates with better outcomes for these recipients.

Functional Outcomes and Satisfaction Rates of Sacral Nerve Stimulation in the Treatment of One and Multiples Pelvic Floor Dysfunctions

Abstract Objective Few studies have addressed the use of sacral nerve stimulation (SNS) in the treatment of patients with multiple pelvic floor dysfunctions (PFD). So, we evaluated the functional outcomes and level of satisfaction with SNS in selected patients with one or multiples PFD. Methods A prospective database was used to collect information on eligible patients treated for PFD with SNS, and severity of symptoms was assessed with scores and satisfaction rates by visual analogue scale (VAS) at baseline and by the end of follow-up. Results We recruited 70 patients, 98.6% of whom responded positively during the evaluation period (Global Response Assessment ≥ 50% for at least one type of PFD), resulting in the implantation of a permanent SNS device. Additionally, 49 of the patients (71%) had a single PFD (fecal incontinence [FI] = 38; constipation/obstructed defecation syndrome [C/ODS] = 11), while 20 (29%) had more than one PFD (double incontinence/n = 12; double incontinence + C/ODS/n = 8). All scores improved significantly between baseline (pre-SNS) and the end of follow-up (post-SNS), as did VAS in all groups (single and multiple PFD). The pre-SNS scores were higher in patients with a single PFD, including FI (Cleveland clinic Florida incontinence score [CCF-FI]) and C/ODS (Cleveland clinic constipation score [C-CCF] and the Renzi ODS score). The pre-SNS impact of VAS scores was similar in all groups (single and multiple PFD), but the VAS (post-SNS) was significantly lower (better response) for FI alone compared with multiple PFD. Conclusion The SNS technique is an effective and safe option for patients with one or more PFD refractory to conservative measures. Response was positive for at least two PFD, based on reduced correspondent scores and satisfaction rate.

ID: 216812 Dynamic Stimulation Patterns Produce Varied Pain Coverage During Acute Spinal Cord Stimulation Evaluation

Introduction: Spinal Cord Stimulation (SCS) for chronic pain management typically uses static stimulation, a.k.a. tonic pulse-trains, where the amplitude, pulse width and rate of stimulation remain the same across time. Several SCS therapies, including both paresthesia-based that typically evoke “tingling” sensations and fast-acting paresthesia-free, are dependent on precise paresthesia-pain overlap. A recent publication demonstrates dynamic stimulation can improve efficacy of SCS in a preclinical rodent model1. We hypothesize that stimulation with dynamic pulse-trains may affect paresthesia-pain overlap. In this work, we evaluated paresthesia coverage of subjects experiencing static and dynamic SCS acutely.

Trigeminal Somatosensory Evoked Potentials During Neurosurgical Procedures Using Electrical Stimulation of the Lips Under General Anesthesia.

Background Intraoperative neurophysiology monitoring is rapidly evolving with the advent of newer modalities. Long latency sensory evoked potentials from the trigeminal nerve distribution have rarely been demonstrated during neurosurgical procedures. Trigeminal sensory evoked potential (TSEP) can be used to prevent nerve injury during surgical procedures, such as those for trigeminal neuralgia and tumors involving the trigeminal nerve and pathway. Methodology We attempted to record TSEP from 12 subjects who underwent various neurosurgical procedures with low doses of inhalational anesthetic agents. We stimulated the upper and lower lip and recorded from C6 and Fz locations. We used 14-17 mA current stimuli with a pulse width of 50-150 microseconds and a stimulation rate of2.1 Hz. Results We could obtain a clear, reproducible TSEP response in two out of 12 subjects. We observed a TSEP waveform with negative peaks at 13 and 27 milliseconds and a positive wave at around 19 milliseconds. Conclusions The TSEP produced by the electrical stimulation of the upper and lower lip can be detected from the scalp C5, C6, and Fz area even during neurosurgical procedures, even if inhalational anesthesia was used at induction, but only in a small proportion of cases. It appeared to reflect the activity of trigeminal cortical response. Avoiding the notch filter and turning off the inhalational agents are essential for a good response.

Cochlear implantation programming characteristics and outcomes of cochlear nerve deficiency.

Due to the specificity of cochlear implantation (CI) programming parameters and outcomes in cochlear nerve deficiency (CND) patients, this study aimed to investigate the correlation between programming parameters and outcomes and further compare the difference between normal and CND groups. Ninety (95 ears) CND patients (normal cochlea, 39; malformed cochlea, 56) and seventy-nine (81 ears) normal cochlea patients who underwent CI surgery with either Med-El or Cochlear devices were included. The programming parameters and outcomes evaluated by the questionnaires were collected and compared among the normal CND, malformed CND, and normal groups in the two device groups, and their correlation was analyzed. In the CND group, a reduced stimulation rate, higher pulse width, and triphasic pulse were needed in some cases. The stimulus levels of the CND group were significantly higher than that of the normal group (p < 0.05), but the outcomes of the CND group were significantly worse than that of the normal group (p < 0.05), and the stimulus level was significantly correlated with the outcomes (p < 0.05). However, there was no difference between normal and malformed CND groups. The non-auditory response was observed in the CND group, especially the ones with malformations. The CI programming parameters of some CND patients need to be adjusted, and a slower stimulation rate and higher pulse width are required sometimes. CND patients need a higher stimulus level than normal patients but their outcomes are poorer. Non-auditory response should be noticed in CND patients during programming.

Adrenal functional reserve in the full spectrum of chronic kidney disease.

Altered cortisol levels have been associated with an increase in mortality and a decrease in health-related quality of life in patients with chronic kidney disease (CKD); however, adrenal response to adrenocorticotropic hormone (ACTH) stimulation test has not been evaluated in patients with stage 3a to 5 CKD with and without renal replacement therapy (RRT). To evaluate adrenal function in patients with CKD. Adults with CKD underwent a low-dose cosyntropin stimulation test (1 µg synthetic ACTH), with serum cortisol levels being measured at 0, +30 and +60 minutes post-test. Sixty participants with stage 3, 4 and 5 CKD (with and without RRT) were included. None of the patients had adrenal insufficiency (AI). The correlation observed between cortisol concentration at baseline and 30 minutes and 1 hour after stimulation and glomerular filtration rate (GFR) was negative and statistically significant (r: -0.39 [p = 0.002], r: -0.363 [p = 0.004], r: -0.4 [p = 0.002], respectively). Since CKD early stages, cortisol levels increase as GFR decreases. Therefore, we conclude that systematic screening for AI is not necessary in CKD patients.

The Effect of Different Stimulation Rates on Brainstem Auditory-Evoked-Potential Responses.

Introduction Auditory-evoked potentials are influenced by several factors, including polarity, filter, stimulus intensity and stimulation rate. The presentation of higher rates of stimuli per second enables the collection of a greater number of responses in a given period of time, promoting a shorter testing time; however, the collected recordings are subject to changes related to wave morphology. Objectives To compare the brainstem auditory-evoked-potential responses with click stimulus with the most commonly used stimulation rates in the clinical practice. Methods The present cross-sectional analytical study was performed with fifteen participants of both genders and normal hearing thresholds. The brainstem auditory-evoked potential was performed at four different stimulation rates (21.1, 26.7, and 27.7 stimuli/s, and a rate determined based on a mathematical calculation using the a measurement of the transmission frequency of the power grid at the time of the examination). Results We observed that the rate of 21.1 stimuli/s showed the highest amplitudes for waves I, III, and V when compared with the other rates. The rate of 26.7 stimuli/s, when compared with 27.7 stimuli/s, showed a higher amplitude for wave V. The latency if wave V was significantly lower with the rate of 21.1 stimuli/s than with 27.7 stimuli/s. Conclusions The stimulation rate interferes with wave latencies and amplitudes; its decrease from 27.7 to 21.1 stimuli/s decreases the latency of wave V and increases the amplitues and improves the morphology of waves I, III and V. In addition, we found evidence that suggests an improvement in the visualization of wave III by adjusting the stimulation rate based on a measurement of the local transmission frequency of the power grid.

Optimization of signal-to-noise ratio in short-duration SEP recordings by variation of stimulation rate

ObjectiveThe intraoperative averaging of the somatosensory evoked potential (SEP) requires reliable recordings within the shortest possible duration. We here systematically optimized the repetition rate of stimulus presentation. MethodsWe recorded medianus and tibial nerve SEP during 22 surgeries and varied the rate of stimulus presentation between 2.7 Hz and 28.7 Hz. We randomly sampled a number of sweeps corresponding to recording durations up to 20 s and calculated the signal-to-noise ratio (SNR). ResultsFor the medianus nerve at 5 s recording duration, SEP stimulation rate at 12.7 Hz obtained the highest median SNR = 22.9 for the N20, which was higher than for rate 4.7 Hz (p = 1.5e-4). When increasing the stimulation rate, latency increased and amplitude decayed for cortical but not for peripheral recording sites. For the tibial nerve, the rate 4.7 Hz achieved the highest SNR for all durations. ConclusionsWe determined the time-dependence of SNR for N20 and elucidated the underlying physiology. For short recordings, rapid reduction of noise through averaging at high stimulation rate outweighs the disadvantage of smaller amplitude. SignificanceFor a short duration of medianus nerve SEP recording only, it may be advantageous to stimulate with a repetition rate of 12.7 Hz.

Lateralization of interaural time differences with mixed rates of stimulation in bilateral cochlear implant listeners.

While listeners with bilateral cochlear implants (BiCIs) are able to access information in both ears, they still struggle to perform well on spatial hearing tasks when compared to normal hearing listeners. This performance gap could be attributed to the high stimulation rates used for speech representation in clinical processors. Prior work has shown that spatial cues, such as interaural time differences (ITDs), are best conveyed at low rates. Further, BiCI listeners are sensitive to ITDs with a mixture of high and low rates. However, it remains unclear whether mixed-rate stimuli are perceived as unitary percepts and spatially mapped to intracranial locations. Here, electrical pulse trains were presented on five, interaurally pitch-matched electrode pairs using research processors, at either uniformly high rates, low rates, or mixed rates. Eight post-lingually deafened adults were tested on perceived intracranial lateralization of ITDs ranging from 50 to 1600 μs. Extent of lateralization depended on the location of low-rate stimulation along the electrode array: greatest in the low- and mixed-rate configurations, and smallest in the high-rate configuration. All but one listener perceived a unitary auditory object. These findings suggest that a mixed-rate processing strategy can result in good lateralization and convey a unitary auditory object with ITDs.

Effect of laparoscopic ovarian cystectomy on ovarian reserve and the outcomes of in vitro fertilization patients with benign ovarian cysts

Objective: To investigate the effect of laparoscopic ovarian cystectomy on anti-Mullerian hormone (AMH) level, ovarian response to gonadotropin stimulation and pregnancy rate for in vitro fertilization (IVF) patients with benign ovarian cysts. Methods: Patients with benign ovarian cysts who were admitted for cystectomy and had undergone IVF treatment were enrolled in the study. There were 373 participants with ovarian cysts underwent laparoscopic ovarian cystectomy in the experimental group. According to duration of post-surgery, there were four sub-groups: 1 year post-surgery (1Y POST), 2 years post-surgery (2Y POST), 4 years post-surgery (4Y POST) and ≥5 years post-surgery (≥5Y POST) in the experimental group. According to histopathologic types of ovarian cysts, there were two sub-groups: ovarian endometriotic cysts and ovarian non-endometriotic cysts. Two hundreds and three patients with no history of ovarian cysts and ovarian surgery were in the control group. The level of AMH and basic concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P), estradiol (E2) were measured. Antral follicle counts (AFC) were calculated. There were other study variables: total dose of gonadotropins, duration of ovarian stimulation, the number of oocyte retrieved, the number of embryo obtained, blastocyst transfer rate and pregnancy rate. Results: The control group was matched as closely as possible to the experimental group, including age, body mass index and menstrual cycle (all P>0.05). Compared to the women in control group, the women in ovarian endometriotic cystectomy sub-group had significantly higher levels of basal FSH and basal P, lower level of AMH (all P<0.05); the women in ovarian endometriotic cysts sub-group had significantly higher dose of gonadotropins (all P<0.05); the women in ovarian endometriotic cysts ≥5Y POST sub-group had significantly lower number of oocyte retrieved, lower number of embryo obtained, lower blastocyst transfer rate, and lower pregnancy rate (all P<0.05). Compared to the women in control group, the women in ovarian non-endometriotic cysts sub-group had a significantly higher level of basal FSH and basal P (all P<0.05). The women in ovarian non-endometriotic cysts sub-group had lower level of AMH, higher dose of gonadotropins, lower number of oocyte retrieved, lower number of embryo obtained, lower rate of blastocyst transfer and lower rate of pregnancy than the control group but there were no statistically significant differences among them (all P>0.05). The women with unilateral ovarian endometriotic cysts had significantly lower number of oocyte retrieved on the side of surgery than another side (P<0.05). Conclusions: In short term laparoscopic ovarian cystectomy has no significant effect on ovarian reserve. But with long-term follow-up ovarian reserve, ovarian response to gonadotropin stimulation and pregnancy rate are decreased. The effect of laparoscopic ovarian cystectomy in benign cysts on ovarian is associated with whether or not it is the surgical side.

Graded optogenetic activation of the auditory pathway for hearing restoration

Optogenetic control of neural activity enables innovative approaches to improve functional restoration of diseased sensory and motor systems. For clinical translation to succeed, optogenetic stimulation needs to closely match the coding properties of the targeted neuronal population and employ optimally operating emitters. This requires the customization of channelrhodopsins, emitters and coding strategies. Here, we provide a framework to parametrize optogenetic neural control and apply it to the auditory pathway that requires high temporal fidelity of stimulation. We used a viral gene transfer of ultrafast targeting-optimized Chronos into spiral ganglion neurons (SGNs) of the cochlea of mice. We characterized the light-evoked response by in vivo recordings from individual SGNs and neurons of the anteroventral cochlear nucleus (AVCN) that detect coincident SGN inputs. Our recordings from single SGNs demonstrated that their spike probability can be graded by adjusting the duration of light pulses at constant intensity, which optimally serves efficient laser diode operation. We identified an effective pulse width of 1.6 ms to maximize encoding in SGNs at the maximal light intensity employed here (∼35 mW). Alternatively, SGNs were activated at lower energy thresholds using short light pulses (<1 ms). An upper boundary of optical stimulation rates was identified at 316 Hz, inducing a robust spike rate adaptation that required a few tens of milliseconds to recover. We developed a semi-stochastic stimulation paradigm to rapidly (within minutes) estimate the input/output function from light to SGN firing and approximate the time constant of neuronal integration in the AVCN. By that, our data pave the way to design the sound coding strategies of future optical cochlear implants.

The contribution of the cervix to sexual response: an online survey study.

The role of the cervix in sexual response has been poorly studied, despite previous research indicating that some women experience pleasurable sexual sensations from cervical stimulation; given previous reports of sexual issues after cervix electrocautery, it is possible that cervical injury may compromise the role of the cervix in sexual functioning. The aims of this study were to examine locations of pleasurable sexual sensations, to identify sexual communication barriers, and to investigate if cervical procedures are associated with negative impacts on sexual function. Women with (n = 72) and without (n = 235) a history of a gynecological procedure completed an online survey assessing demographics, medical history, sexual function (including locations of sexual pleasure and pain on diagrams), and barriers. The procedure group was divided into subgroups of those who had experienced a cervical (n = 47) or noncervical (n = 25) procedure. Chi-square analyses and t tests were conducted. Outcomes included locations and ratings of pleasurable and painful sexual stimulation, as well as sexual function. Over 16% of participants reported experiencing some pleasurable sexual sensations from the cervix. The gynecological procedure group (n = 72) reported significantly higher pain in the vagina and lower rates of pleasure in their external genitals, vagina, deep vagina, anterior and posterior vaginal walls, and clitoris vs the non-gynecological procedure (n = 235) group. The gynecological procedure group and the cervical procedure subgroup (n = 47) reported significant decreases in desire, arousal, and lubrication and increased avoidance of sexual activity due to vaginal dryness. The gynecological procedure group reported significant pain with vaginal stimulation, whereas the cervical subgroup identified significant pain with cervical and clitoral stimulation. Cervical stimulation elicits some pleasurable sexual sensations for many women, and gynecological procedures that affect the cervix are associated with pain and sexual issues; thus, health care providers should counsel patients about the possibility of related sexual concerns. This study is the first to examine locations of pleasure and pain and experiences of sexual pleasure and function in participants who underwent a gynecological procedure. A hybrid measure was used to assess sexual issues, including symptoms of dysfunction. Results indicate an association between cervical procedures and sexual issues, supporting the need to inform patients of this possibility following cervical procedures.

On the Effect of High Stimulation Rates on Temporal Loudness Integration in Cochlear Implant Users.

Long stimuli have lower detection thresholds or are perceived louder than short stimuli with the same intensity, an effect known as temporal loudness integration (TLI). In electric hearing, TLI for pulse trains with a fixed rate but varying number of pulses, i.e. stimulus duration, has mainly been investigated at clinically used stimulation rates. To study the effect of an overall effective stimulation rate at 100% channel crosstalk, we investigated TLI with (a) a clinically used single-channel stimulation rate of 1,500 pps and (b) a high stimulation rate of 18,000 pps, both for an apical and a basal electrode. Thresholds (THR), a line of equal loudness (BAL), and maximum acceptable levels (MALs) were measured in 10 MED-EL cochlear implant users. Stimulus durations varied from a single pulse to 300 ms long pulse trains. At 18,000 pps, the dynamic range (DR) increased by dB for the 300 ms pulse train. Amplitudes at THR, BAL, and MAL decreased monotonically with increasing stimulus duration. The decline was fitted with high accuracy with a power law function (). Threshold slopes were and dB per doubling of duration for the low and high rate, respectively, and were shallower than for acoustic hearing. The electrode location did not affect the amplitudes or slopes of the TLI curves. THR, BAL, and MAL were always lower for the higher rate and the DR was larger at the higher rate at all measured durations.

Dynamic accentuated antagonism of heart rate control during different levels of vagal nerve stimulation intensity in rats.

Accentuated antagonism refers to a phenomenon in which the vagal effect on heart rate (HR) is augmented by background sympathetic tone. The dynamic aspect of accentuated antagonism remains to be elucidated during different levels of vagal nerve stimulation (VNS) intensity. We performed VNS on anesthetized rats (n = 8) according to a binary white noise signal with a switching interval of 500 ms at three different stimulation rates (low-intensity: 0-10 Hz, moderate-intensity: 0-20 Hz, and high-intensity: 0-40 Hz). The transfer function from VNS to HR was estimated with and without concomitant tonic sympathetic nerve stimulation (SNS) at 5 Hz. The asymptotic low-frequency (LF) gain (in beats/min/Hz) of the transfer function increased with SNS regardless of the VNS rate [low-intensity: 3.93 ± 0.70 vs. 5.82 ± 0.65 (P = 0.021), moderate-intensity: 3.87 ± 0.62 vs. 5.36 ± 0.53 (P = 0.018), high-intensity: 4.77 ± 0.85 vs. 7.39 ± 1.36 (P = 0.011)]. Moreover, SNS slightly increased the ratio of high-frequency (HF) gain to the LF gain. These effects of SNS were canceled by the pretreatment of ivabradine, an inhibitor of hyperpolarization-activated cyclic nucleotide-gated channels, in another group of rats (n = 6). Although background sympathetic tone antagonizes the vagal effect on mean HR, it enables finer HR control by increasing the dynamic gain of the vagal HR transfer function regardless of VNS intensity. When interpreting the HF component of HR variability, the augmenting effect from background sympathetic tone needs to be considered.

Adding Core Muscle Contraction to Wrist-Ankle Rhythmical Skeletal Muscle Tension Increases Respiratory Sinus Arrhythmia and Low-Frequency Power.

Paced breathing and rhythmical skeletal muscle tension (RSMT) at an individual's resonance frequency [~ 6 breaths or contractions per min (cpm)] can stimulate the arterial and vascular tone baroreflexes. Lehrer (Appl Psychophysiol Biofeedback 1-10, 2022, https://doi.org/10.1007/s10484-022-09535-5 ) has explained that the stimulation rate is important, not the modality. Early RSMT protocols differed in the muscles recruited and whether legs were crossed or uncrossed (in France et al. Clin Physiol Funct Imaging 26: 21-25, 2006, https://doi.org/10.1111/j.1475-097X.2005.00642.x ; Leher et al. Biol Psychol 81: 24-30, 2009, https://doi.org/10.1016/j.biopsycho.2009.01.003 ; Vaschillo et al. Psychophysiology, 48: 927-936, 2011, https://doi.org/10.1111/j.1469-8986.2010.01156.x ). Whereas core muscle RSMT with crossed legs and wrist-ankle RSMT with uncrossed legs produced resonance effects, researchers have not directly compared the effect of these exercises on respiratory sinus arrhythmia (RSA) and low-frequency (LF) power. The current within-subjects experiment investigated whether crossing the legs and recruiting core muscles enhances wrist-ankle RSMT effects on RSA and LF power. We trained 35 participants to complete 6-cpm wrist-ankle RSMT (ankles uncrossed), 6-cpm wrist-core-ankle RSMT (ankles crossed), and a control condition in which participants sat quietly (ankles uncrossed) without performing RSMT. We predicted that 6-cpm wrist-core-ankle RSMT would produce greater heart rate (HR), HR Max-HR Min, and LF power than the other conditions. The experimental findings supported our predictions. Both RSMT conditions produced greater HR, HR Max-HR Min, and LF power than the control condition. Wrist-core-ankle yielded greater HR and HR Max-HR Min than wrist-ankle RSMT. Future research should compare wrist-ankle and wrist-core-ankle RSMT with legs crossed. The practical implication for HRV biofeedback training is that wrist-core-ankle RSMT with legs crossed may more powerfully stimulate the baroreflex than wrist-ankle RSMT with legs uncrossed.

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro.

Neuromuscular efficiency is defined as the ratio of work output to stimulation rate. The purpose of these experiments was to test the hypothesis that neuromuscular efficiency would be increased in proportion to posttetanic potentiation, that is, the stimulation-induced increase in work output displayed by rodent fast-twitch muscle. To this end, extensor digitorum longus muscles from wild-type and skeletal myosin light chain kinase knockout (skMLCK-/- ) mice were surgically isolated and suspended in vitro (25°C). Concentric force development during shortening at 70% of maximal unloaded shortening velocity was tested at stimulus frequencies between 10 and 80 Hz both before and after a potentiating tetanus. A strong genotype-dependent difference in the potentiation of concentric work output was observed; concentric work output of wild-type muscles was increased by 51%-88% while that of skMLCK-/- muscles was increased by only 20%-34% across the frequencies tested. As a result, comparison of work - frequency plots revealed that the frequency required for peak and 50% peak unpotentiated work of wild-type muscles was decreased from ~80 to 52 Hz and from ~48 to 21 Hz, respectively. By contrast, the frequency required for peak and 50% peak unpotentiated work of skMLCK-/- muscles was decreased from ~80 to 68 Hz and from ~51 to 41 Hz, respectively. Thus, wild-type muscles with the ability to phosphorylate myosin displayed larger increases in neuromuscular efficiency than skMLCK-/- muscles (25-30 vs 10-15 Hz, respectively). This suggests that the presence of myosin phosphorylation may ameliorate or mitigate fatigue mechanisms associated with high-frequency stimulation rates.

Temporal frequency dependence of the polarity inversion between upper and lower visual field in the pattern-onset steady-state visual evoked potential

PurposeAccording to the cruciform model, the upper and lower halves of the visual field representation in the primary visual cortex are located mainly on the opposite sides of the calcarine sulcus. Such a shape would have consequences for the surface-recorded visual evoked potential (VEP), as V1 responses to stimulation of the upper and lower hemifield manifest with opposite polarity (i.e., polarity inversion). However, the steady-state VEP results from a complex superposition of response components from different cortical sources, which can obscure the inversion of polarity. The present study assesses the issue for different stimulation frequencies which result in different patterns of superposition in the steady-state response.MethodsSequences of brief pattern-onset stimuli were presented at different stimulation rates ranging from 2 Hz (transient VEP) to 13 Hz (steady-state VEP). The upper and lower hemifields were tested separately and simultaneously. The data were assessed both in the time domain and in the frequency domain.ResultsComparing the responses to the stimulation of upper and lower hemifield, polarity inversion was present within a limited time interval following individual stimulus onsets. With increasing frequency, this resulted in an approximate inversion of the full steady-state response and consequently in a phase shift of approximately 180° in the time-domain response. Polarity inversion was more prominent at electrode Pz, also for transient responses. Our data also demonstrated that the sum of the hemifield responses is a good approximation of the full-field response.ConclusionWhile the basic phenomenon of polarity inversion occurs irrespective of the stimulus frequency, its relative impact on the steady-state response as a whole is the largest for high stimulation rates. We propose that this is because longer-lasting response components from other visual areas are not well represented in the steady-state VEP at higher frequencies.

Misconceptions in IONM Part III: Stimulation Repetition Rate Effects on Intraoperative Somatosensory Evoked Potential Amplitude and Latency

ABSTRACT The rate at which stimulation is applied to peripheral nerves is critical to generating high-quality intraoperative somatosensory evoked potentials (SSEPs) in a timely manner. Guidelines based on a limited study and anecdotal evidence present differing, incorrect, or incomplete stimulation rate recommendations. We examined the effect stimulating the ulnar and tibial nerves at 1.05, 2.79, 5.69, and 8.44 Hz had on cortical, subcortical, and peripheral response amplitude and latency in 10 subjects with neuromuscular blockade (NMB) and 10 without NMB in the operating room under general anesthesia. As the stimulation repetition rate increased, the amplitude of upper and lower extremity cortical responses decreased equally in both groups. The ulnar nerve N20 cortical response amplitude decreased 27.9% at 2.79 Hz, 48.8% at 5.69 Hz, and 53.8% at 8.44 Hz. The tibial nerve P37 cortical response amplitude decreased 30.3% at 2.79 Hz, 53.8% at 5.69 Hz, and 56.8% at 8.44 Hz. Neither upper or lower extremity peripheral or subcortical amplitudes nor upper and lower extremity subcortical or peripheral latencies were affected by increasing repetition rate in either group. Low SSEP stimulation repetition rates ensure the highest quality cortical responses.