Pacing Conditions Research Articles

Noninvasive Personalization of a Cardiac Electrophysiology Model From Body Surface Potential Mapping.

We use noninvasive data (body surface potential mapping, BSPM) to personalize the main parameters of a cardiac electrophysiological (EP) model for predicting the response to different pacing conditions. First, an efficient forward model is proposed, coupling the Mitchell-Schaeffer transmembrane potential model with a current dipole formulation. Then, we estimate the main parameters of the cardiac model: activation onset location and tissue conductivity. A large patient-specific database of simulated BSPM is generated, from which specific features are extracted to train a machine learning algorithm. The activation onset location is computed from a Kernel Ridge Regression and a second regression calibrates the global ventricular conductivity. The evaluation of the results is done both on a benchmark dataset of a patient with premature ventricular contraction (PVC) and on five nonischaemic implanted cardiac resynchonization therapy (CRT) patients with a total of 21 different pacing conditions. Good personalization results were found in terms of the activation onset location for the PVC (mean distance error, MDE = 20.3mm), for the pacing sites (MDE = 21.7 mm) and for the CRT patients (MDE = 24.6 mm). We tested the predictive power of the personalized model for biventricular pacing and showed that we could predict the new electrical activity patterns with a good accuracy in terms of BSPM signals. We have personalized the cardiac EP model and predicted new patient-specific pacing conditions. This is an encouraging first step towards a noninvasive preoperative prediction of the response to different pacing conditions to assist clinicians for CRT patient selection and therapy planning.

Mechanical Stress Conditioning and Electrical Stimulation Promote Contractility and Force Maturation of Induced Pluripotent Stem Cell-Derived Human Cardiac Tissue.

Tissue engineering enables the generation of functional human cardiac tissue with cells derived in vitro in combination with biocompatible materials. Human-induced pluripotent stem cell-derived cardiomyocytes provide a cell source for cardiac tissue engineering; however, their immaturity limits their potential applications. Here we sought to study the effect of mechanical conditioning and electric pacing on the maturation of human-induced pluripotent stem cell-derived cardiac tissues. Cardiomyocytes derived from human-induced pluripotent stem cells were used to generate collagen-based bioengineered human cardiac tissue. Engineered tissue constructs were subjected to different mechanical stress and electric pacing conditions. The engineered human myocardium exhibits Frank-Starling-type force-length relationships. After 2 weeks of static stress conditioning, the engineered myocardium demonstrated increases in contractility (0.63±0.10 mN/mm2 vs 0.055±0.009 mN/mm2 for no stress), tensile stiffness, construct alignment, and cell size. Stress conditioning also increased SERCA2 (Sarco/Endoplasmic Reticulum Calcium ATPase 2) expression, which correlated with a less negative force-frequency relationship. When electric pacing was combined with static stress conditioning, the tissues showed an additional increase in force production (1.34±0.19 mN/mm2), with no change in construct alignment or cell size, suggesting maturation of excitation-contraction coupling. Supporting this notion, we found expression of RYR2 (Ryanodine Receptor 2) and SERCA2 further increased by combined static stress and electric stimulation. These studies demonstrate that electric pacing and mechanical stimulation promote maturation of the structural, mechanical, and force generation properties of human-induced pluripotent stem cell-derived cardiac tissues.

Influence of pacing on reliability of middle-distance cycling performance

The purpose of the present study was to examine the reliability of middle distance cycling time trials using fast-, even-, and slow-starts . Eighteen endurance-trained male cyclists [mean ± standard deviation; VO 2peak 63.1 ± 6.1 mL ⋅ kg -1 ⋅ min -1 ] performed nine cycling time trials where the total external work (96.5 ± 11.2 kJ) was identical to the better of two, 5-minute habituation time trials. Power output during the first quarter of the time-trials (24.1 ± 2.8 kJ) was fixed to induce fast-, even- or slow-starting strategies (60, 75 and 90 s, respectively). In consecutive sessions, participants performed three trials of each pacing condition although the order of these pacing conditions was counterbalanced. Average power output and performance time were unaffected by trial number in the fast- (P = 0.60), even- (P = 0.18) and slow-start (P = 0.53) trials. In all three pacing conditions, average power output was highly reliable and similar between trial 1 to 2 and trial 2 to 3 in fast- (standard error of measurement; SEM=8.3 and 8.2W), even (coefficient of variation; CV=2.8 and 2.4%) and slow-start (CV=2.4 and 1.5%) trials. In conclusion, the reproducibility of 5-min cycling time trials is unaffected by starting strategy and is acceptable following two self- paced habituation trials. Research examining the influence of pacing strategies may therefore be conducted without the need for familiarisation trials using each individual pacing condition.

0307 : Acute activation of the hexosamine biosynthetic pathway promotes electrical instability

The hexosamine biosynthetic pathway (HBP) is heightened in cardiomyopathies. We aimed at understanding how over-activation of HBP impacts on cardiac electrophysiology, and acts as a trigger or a substrate of cardiac arrhythmias. Overactivation of the HBP by injection of glucosamine (GlcN 270mg/kg) was assessed under basal conditions and during beta-adrenergic stress on the myocardial energetic status (phosphocreatine to ATP ratio) of rats by 31 P nuclear magnetic resonance spectroscopy. Rat hearts were perfused ex vivo to evaluate the effects of the HBP activation (physiologically: glutamine 0.5mM – gln; overactivated: GlcN 1mM) on: cardiac function, MVO 2 , and arrhythmia score (AS) under basal (spontaneous arrhythmias: sAS) and pacing (pAS) conditions. At the cellular level (HL1 cells), HBP overactivation (GlcN) was assessed on conduction velocity characterized by micro-electrode arrays recordings, and properties of voltage gated ionic channels involved in cellular excitability and conduction by patch clamp experiments. In vivo GlcN did not modify PCr/ATP of the left ventricle under basal conditions. This ratio was significantly decreased during beta-adrenergic stress, while a similar increased heart rate was reported. When hearts were isolated and perfused ex vivo , GlcN induced a decrease of the heart rate and MVO 2 temporarily, and an increase of the sAS and pAS. Physiological activation of HBP with gln did not impact the ex vivo cardiac function and the sAS, but further increased the probability of atrial arrhythmias during pacing. In HL1 cells, GlcN reduced the rate of spontaneous depolarization, modified the direction and the velocity of the impulse propagation, and altered activation and inactivation properties of the sodium channel. Acute HBP activation is associated with an increased vulnerability for arrhythmias and alteration of impulse conduction, suggesting its potential role in the atrial and ventricular arrhythmias. The author hereby declares no conflict of interest

Major League Baseball pace-of-play rules and their influence on predicted muscle fatigue during simulated baseball games

ABSTRACTMajor League Baseball (MLB) has proposed rule changes to speed up baseball games. Reducing the time between pitches may impair recovery from fatigue. Fatigue is a known precursor to injury and may jeopardise joint stability. This study examined how fatigue accumulated during baseball games and how different pace of play initiatives may influence fatigue. Pitcher data were retrieved from a public database. A predictive model of muscle fatigue estimated muscle fatigue in 8 arm muscles. A self-selected pace (22.7 s), 12 s pace (Rule 8.04 from the MLB) and a 20 s rest (a pitch clock examined in the 2014 Arizona Fall League (AFL)) were examined. Significantly more muscle fatigue existed in both the AFL and Rule 8.04 conditions, when compared to the self-selected pace condition (5.01 ± 1.73%, 3.95 ± 1.20% and 3.70 ± 1.10% MVC force lost, respectively). Elevated levels of muscle fatigue are predicted in the flexor–pronator mass, which is responsible for providing elbow stability. Reduced effectiveness of the flexor–pronator mass may reduce the active contributions to joint rotational stiffness, increasing strain on the ulnar collateral ligament (UCL) and possibly increasing injury risk.

Flow and enjoyment beyond skill-demand balance: The role of game pacing curves and personality

According to flow theory, skill-demand balance is optimal for flow. Experimentally, balance has been tested only against strong overload and strong boredom. We assessed flow and enjoyment as distinct experiences and expected that they (a) are not optimized by constant balance, (b) experimentally dissociate, and (c) are supported by different personality traits. Beyond a constant balance condition (“balance”), we realized two dynamic pacing conditions where demands fluctuated through short breaks: one condition without overload (“dynamic medium”) and another with slight overload (“dynamic high”). Consistent with assumptions, constant balance was not optimal for flow (balance ≤ dynamic medium < dynamic high) and enjoyment (balance ≤ dynamic high < dynamic medium). Action orientation enabled high flow even under the suboptimal condition of balance. Sensation seeking increased enjoyment under the suboptimal but arousing dynamic high condition. We discuss dynamic changes in positive affect (seeking and mastering challenge) as an integral part of flow.

Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

The central nervous system has the ability to adapt our locomotor pattern to produce a wide range of gait modalities and velocities. In reacting to external pacing stimuli, deviations from an individual preferred cadence provoke a concurrent decrease in accuracy that suggests the existence of a trade-off between frequency and precision; a compromise that could result from the specialization within the control centers of locomotion to ensure a stable transition and optimal adaptation to changing environment. Here, we explore the neural correlates of such adaptive mechanisms by visually guiding a group of healthy subjects to follow three comfortable stepping frequencies while simultaneously recording their BOLD responses and lower limb kinematics with the use of a custom-built treadmill device. In following the visual stimuli, subjects adopt a common pattern of symmetric and anti-phase movements across pace conditions. However, when increasing the stimulus frequency, an improvement in motor performance (precision and stability) was found, which suggests a change in the control mode from reactive to predictive schemes. Brain activity patterns showed similar BOLD responses across pace conditions though significant differences were observed in parietal and cerebellar regions. Neural correlates of stepping precision were found in the insula, cerebellum, dorsolateral pons and inferior olivary nucleus, whereas neural correlates of stepping stability were found in a distributed network, suggesting a transition in the control strategy across the stimulated range of frequencies: from unstable/reactive at lower paces (i.e., stepping stability managed by subcortical regions) to stable/predictive at higher paces (i.e., stability managed by cortical regions). Hum Brain Mapp 37:1722-1737, 2016. © 2016 Wiley Periodicals, Inc.

Analysis of Activation-Recovery Intervals from Intracardiac Electrograms in Normal and Infarcted Porcine Hearts

Mapping of intracardiac electrical signals is a well-established clinical method used to identify the foci of abnormal heart rhythms associated with chronic myocardial infarct (a major cause of death). These foci reside in the ‘border zone’ (BZ) between healthy tissue and dense collagenous scar, and are the targets of ablation therapy. In this work we analyzed detailed features of the electrical signals recorded in a translational animal model of chronic infarct. Specifically, three-dimensional activation maps and bipolar voltages were recorded in vivo from 8 pigs at 5-6 weeks following infarct creation, as well as 7 control (normal) pigs. Endocardial and epicardial maps were obtained during normal sinus rhythm and/or pacing conditions via a catheter-based electro-anatomical CARTO-XP mapping system (Biosense, Webster). Next, depolarization and repolarization maps were derived through manual annotation of electro-cardiogram waves, where the peak of the QRS wave marked the time of depolarization and the peak of the T wave marked the recovery time. Then, at each recording point, activation-recovery intervals (ARI) were found by subtracting activation times from repolarization times. Such ARI maps are important clinical surrogates of action potential duration. Overall, we observed that ARI values in the BZ have recovered from the acute stage and were close to ARI values in normal tissue. Furthermore, in both infarcted and normal cases we observed: i) a weak negative correlation between the activation times and ARI values, and ii) not a significant variation (p<0.5) between mean ARI values in the BZ area and those in the healthy areas. Our future work will focus on personalizing mathematical models from these electrical maps per individual hearts, to enable accurate predictions of cardiac wave propagation and the inducibility of scar-related abnormal rhythms.

Abstract 11125: Increasing Stimulus Strength of Coronary Sinus Pacing Improved Left Ventricular Mechanical Dyssynchrony and Contractile Function in Patients With Reduced Ejection Fraction

Introduction: Increasing stimulus strength of left ventricular (LV) coronary sinus pacing decreases QRS duration and inter-ventricular conduction time. Hypothesis: Increasing stimulus strength of LV coronary sinus pacing improves LV mechanical dyssynchrony and myocardial function. Methods: We studied 36 patients with 6±4 months after cardiac resynchronization therapy (LV ejection fraction: 39±11%). The LV pacing lead was positioned in lateral or posterolateral coronary sinus vein. We measured standard deviation (SD) of time to negative peak circumferential strain (time-CircS) in 6 segments and peak global circumferential strain value (CircS) using two-dimensional speckle-tracking echocardiography to evaluate LV mechanical dyssynchrony and myocardial contractile function, respectively. Low (1.3±0.6V), clinical (2.6±1.0V), and high (7.3±1.1V) voltage conditions of LV coronary sinus pacing were performed under right ventricular pacing-off. Results: SD of time-CircS and global CircS under high voltage LV coronary sinus pacing was significantly better than those under low and clinical voltage (78±38 vs. 90±48 and 92±43msec, p=0.014 and 0.016; 5.7±3.4 vs. 5.4±3.3 and 5.4±3.4%, p=0.007 and 0.003). Moreover, global CircS significantly correlated with SD of time-CircS (r= -0.54, p&lt;0.001, n=108). Conclusions: Increasing stimulus strength of LV coronary sinus pacing improved LV mechanical dyssynchrony and LV contractile function, leading clinical implication for better management of heart failure patients with cardiac resynchronization therapy.

Perceptuo-motor compatibility governs multisensory integration in bimanual coordination dynamics.

The brain has the remarkable ability to bind together inputs from different sensory origin into a coherent percept. Behavioral benefits can result from such ability, e.g., a person typically responds faster and more accurately to cross-modal stimuli than to unimodal stimuli. To date, it is, however, largely unknown whether such multisensory benefits, shown for discrete reactive behaviors, generalize to the continuous coordination of movements. The present study addressed multisensory integration from the perspective of bimanual coordination dynamics, where the perceptual activity no longer triggers a single response but continuously guides the motor action. The task consisted in coordinating anti-symmetrically the continuous flexion-extension of the index fingers, while synchronizing with an external pacer. Three different configurations of metronome were tested, for which we examined whether a cross-modal pacing (audio-tactile beats) improved the stability of the coordination in comparison with unimodal pacing condition (auditory or tactile beats). We found a more stable bimanual coordination for cross-modal pacing, but only when the metronome configuration directly matched the anti-symmetric coordination pattern. We conclude that multisensory integration can benefit the continuous coordination of movements; however, this is constrained by whether the perceptual and motor activities match in space and time.

Impact de la redondance verbale et du contrôle du document pendant l’apprentissage multimédia

We analyzed the effects of redundancy arising from the duplication of spoken information in writing during the learning of a multimedia document, and sought to determine whether these effects persist when students can control the pace of presentation. In line with our hypotheses, results showed that verbal redundancy resulted in poorer performances. However, this effect was limited to the quality of diagram completion and did not show up either in a recall task or in a transfer task. The students who were able to peruse the document at their own pace spent far longer processing it, especially in the verbal redundancy condition, but there was no attendant improvement in learning. Contrary to our hypotheses, the negative impact of redundancy on diagram completion did not disappear in the pacing condition. We discuss these results in terms of strategies for compensating for the processing difficulties that arise from having to divide attention between multiple visual sources in a redundancy condition.

A Novel Classification Method with Superior Prediction of Drug Arrhythmia Risk

Many drugs, both cardiac and non-cardiac, cause fatal arrhythmias. Current assays to evaluate arrhythmia risk based on block of the delayed rectifier K+ current (hERG) and QT interval prolongation are limited by poor specificity. We hypothesize that physiological, dynamical simulations of drug effects on heart cells will yield better algorithms to discriminate between arrhythmogenic and safe drugs. To test this, we model drug action in cardiomyocyte models based on drug interaction with 3 cardiac ion channels: hERG, the L-type Ca2+ channel, and the fast Na+ channel. For 67 distinct drugs, we measure 15 cellular physiological metrics under multiple pacing conditions and in the 3 ventricular cell types, each in 3 human ventricular cell models. Additionally, we evaluate the influences of gender and inter-individual variability on risk by conducting simulations in both female and male models, and in a simulated population of individuals, respectively. Principal component analysis of these drug effect metrics reveals distinct behaviors of arrhythmogenic drugs. This segregation of drugs in principal component space facilitates their classification into arrhythmogenic and safe categories. Our classification by this method is more sensitive and specific than the hERG block assay or, to our knowledge, any other published predictors, with an area under the receiver-operator characteristic of 0.9630. Furthermore, because it is based on cellular physiological metrics, our algorithm can predict the arrhythmogenicity of drugs with a range of cardiac molecular targets, beyond those of the drugs used to train the algorithm. In conclusion, we have developed a classification algorithm using dynamical heart cell models, suitable for cardiac safety assessments early in drug development, that outperforms current methods in the discrimination of arrhythmogenic and safe drugs.

Rate-Related Kinematic Changes in Younger and Older Adults

Aims: This study aimed to investigate the effects of speech rate changes on kinematic characteristics and stability of speech movements in younger and older speakers using electromagnetic midsagittal articulography. Patients and Methods: Eight young adults and 8 older adults engaged in a series of syllable repetition tasks of /pa/, /sa/ and /ta/ obtained at self-paced slow, habitual and fast speech rates, as well as in a series of metronome-guided speech rates, ranging from 2 to 4 syllables per second. The kinematic parameters duration, amplitude and peak velocity were obtained for opening and closing movements. Results: Older speakers were able to increase speech rate to the same degree or higher compared to younger speakers in both pacing conditions. Kinematic data show that older adults increased duration and decreased peak velocity in closing movements of alveolar constrictions at slower rates more prominently than younger adults. The results on movement stability revealed no differences between age groups. Conclusions: The results suggest that an age-related difference in speed-accuracy trade-off can be ruled out. Differences in kinematic characteristics point towards the possibility that older adults aimed to facilitate a closed-loop control system to maintain movement stability at slower speech rates.

Dynamic Tracking of a 2.4GHz Waist Mounted Beacon for Indoor Basketball Player Positioning

Wireless player tracking is being considered for use within indoor team sports for coaching assistance. Few research studies exist into wireless RF signal tracking of players in indoor team sports, in particular the game of basketball. Utilising the RF signal trilateration positioning technique with three anchor nodes per quarter court, players wearing RF beacons could be tracked and their positional data recorded in real time. This study builds on a previous study conducted under static conditions by Kirkup et al. (2013). Identifying the player with the ball is also important in recording and assessing team strategies. Accelerometer sensors located on the body have been widely used to monitor the movements of the body and can potentially be used to recognize when a player is bouncing the basketball (dribbling). This paper reports the findings of using the received signal strength positioning technique with one anchor node to estimate the position of a moving basketball player towards the node and the use of a wearable triaxial accelerometer sensor to identify the person bouncing the ball. Both slow and fast game pace conditions are tested. Player position accuracy can be achieved to within 0.5m for distances less than 9m. A study of the power law variation in signal strength over distance gives an exponent n of 2.23 under moderate paced conditions with a Pearson squared correlation coefficients of r2 = 0.42. This means that 42% of the variation can be explained by the approximation. Under moving conditions, changes in the transmit antenna orientation will result in an increase of random variation in position prediction which is included in this result. The acceleration signature from a wrist sensor of the hand-ball contact process while dribbling distinctively shows ball dribbling possession. A single moving player scenario is discussed and measured results with and without the basketball demonstrate the accuracy and feasibility of the positioning and ball possession techniques. The techniques will provide valuable information for further study into multiple player and multiple beacon wireless indoor positioning.

Chronic low back pain sufferers exhibit freezing-like behaviors when asked to move their trunk as fast as possible

Background contextThe effect of chronic low back pain (CLBP) on the kinematic parameters of trunk motion has received much more interest in this last decade. However, there are no descriptions of the motor strategies that occur when patients perform trunk movements in the three anatomical planes at different pace conditions. PurposeTo investigate motor strategies used by CLBP patients and asymptomatic people while performing different go and back trunk movements in an upright standing position. Study designA comparative study. Patient sampleThe control group (CG, n=33) included 14 men and 19 women with no history of low back pain, and the chronic low back pain group (CLBPG, n=49) included 21 men and 28 women. Outcome measuresKinematic data were analyzed during six trunk movements: flexion, extension, left and right lateral bendings, and rotations under two pace conditions (preferred and fast paces). MethodsA three-dimensional optoelectronic motion analysis system was used to assess static (trunk inclinations and base of support) and dynamic (range of motion [ROM] and mean angular velocity of the trunk) parameters during the go and back phases of trunk movements. ResultsIn the initial position, CLBPG showed a more forward-tilted trunk inclination (2.1°±1.1°, p=.013) compared with CG. The base of support was significantly higher in CG (+22.7 cm2, p=.009) during the fast pace when compared with the preferred pace. Regardless of the pace condition, ROM and mean angular velocity of the trunk were significantly lower in CLBPG for all examined movements and the pace condition did not significantly alter ROM. At the preferred pace, both groups displayed the same motor strategy: they all went faster during the second phase of movement than during the first phase. However, at the fast pace, while CG was going faster during the first phase than during the second, CLBPG maintained the same motor strategy as at the preferred pace. ConclusionsContrary to CG who changed its motor behavior from a preferred pace to a fast pace, CLBPG exhibited freezing-like behaviors. This original result highlights the importance of studying the velocity. The use of this parameter may improve the diagnosis of CLBP patients and could be a key indicator for treatment progress and long-term monitoring.

Effectiveness of epicardial atrial pacing using a bipolar steroid-eluting endocardial lead with active fixation in an experimental model

To assess the effectiveness of bipolar epicardial atrial pacing using an active fixation bipolar endocardial lead implanted on the atrial surface in an experimental model. A total of ten Large White adult pigs underwent pacemaker implantation under general anesthesia. Atrial pacing and sensing parameters were obtained at the procedure, immediate postoperative period and on the 7th and the 30th postoperative in unipolar and bipolar configurations. All procedures were successfully performed. There were no perioperative complications and no early deaths. Atrial pacing and sensing parameters for both unipolar and bipolar modes remained stable throughout the study. We observed a progressive increase in atrial thresholds, ranging from 0.49 ± 0.35 (at implantation) to 1.86 ± 1.31 volts (30th postoperative day), in unipolar mode. Atrial impedance measurements decreased slightly over time, ranging from 486.80 ± 126.35 Ohms (at implantation) to 385.0 ± 80.52 Ohms (30th postoperative day). Atrial sensing measures remained stable from the immediate postoperative period until the end of the study. The bipolar active fixation endocardial lead implanted epicardially can provide stable conditions of pacing and sensing parameters throughout the postoperative follow-up.

RAnoLazIne for the Treatment of Diastolic Heart Failure in Patients With Preserved Ejection Fraction: The RALI-DHF Proof-of-Concept Study

This study investigated whether inhibiting late Na(+) current by using ranolazine improved diastolic function in patients with heart failure with preserved ejection fraction (HFpEF). HFpEF accounts for >50% of all HF patients, but no specific treatment exists. The RALI-DHF (RAnoLazIne for the Treatment of Diastolic Heart Failure) study was a prospective, randomized, double-blind, placebo-controlled small proof-of-concept study. Inclusion criteria were EF≥45%, a mitral E-wave velocity/mitral annular velocity ratio (E/E') >15 or N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentration >220 pg/ml, a left ventricular end-diastolic pressure (LVEDP)≥18 mm Hg, and time-constant of relaxation (tau)≥50 ms. Patients were randomized to ranolazine (n= 12) or placebo (n= 8). Treatment consisted of intravenous infusion for 24 h, followed by oral treatment for 13 days. After 30 min of infusion, LVEDP (p= 0.04) and pulmonary capillary wedge pressure (p= 0.04) decreased in the ranolazine group but not in the placebo group. Mean pulmonary artery pressure showed a trend toward a decrease in the ranolazine group that was significant under pacing conditions at 120 beats/min (p= 0.02), but not for the placebo group. These changes occurred without changes in left ventricular end-systolic pressure or systemic or pulmonary resistance but in the presence of a small but significant decrease in cardiac output (p= 0.04). Relaxation parameters (e.g., tau, rate of decline of left ventricular pressure per minute [dP/dtmin]) were unaltered. Echocardiographically, the E/E' ratio did not significantly change after 22 h. After 14 days of treatment, no significant changes were observed in echocardiographic or cardiopulmonary exercise test parameters. There were no significant effects on NT-pro-BNP levels. Results of this proof-of-concept study revealed that ranolazine improved measures of hemodynamics but that there was no improvement in relaxation parameters. (Ranolazine in Diastolic Heart Failure [RALI-DHF]; NCT01163734).

Evaluation of techniques for estimating the power spectral density of RR-intervals under paced respiration conditions

Heart rate variability (HRV) analysis is increasingly used in anaesthesia and intensive care monitoring of spontaneous breathing and mechanical ventilated patients. In the frequency domain, different estimation methods of the power spectral density (PSD) of RR-intervals lead to different results. Therefore, we investigated the PSD estimates of fast Fourier transform (FFT), autoregressive modeling (AR) and Lomb-Scargle periodogram (LSP) for 25 young healthy subjects subjected to metronomic breathing. The optimum method for determination of HRV spectral parameters under paced respiration was identified by evaluating the relative error (RE) and the root mean square relative error (RMSRE) for each breathing frequency (BF) and spectral estimation method. Additionally, the sympathovagal balance was investigated by calculating the low frequency/high frequency (LF/HF) ratio. Above 7 breaths per minute, all methods showed a significant increase in LF/HF ratio with increasing BF. On average, the RMSRE of FFT was lower than for LSP and AR. Therefore, under paced respiration conditions, estimating RR-interval PSD using FFT is recommend.

Influence of Pacing by Periodic Auditory Stimuli on Movement Continuation: Comparison with Self-regulated Periodic Movement

[Purpose] The purpose of this study was to investigate the influence of external pacing with periodic auditory stimuli on the control of periodic movement. [Subjects and Methods] Eighteen healthy subjects performed self-paced, synchronization-continuation, and syncopation-continuation tapping. Inter-onset intervals were 1,000, 2,000 and 5,000 ms. The variability of inter-tap intervals was compared between the different pacing conditions and between self-paced tapping and each continuation phase. [Results] There were no significant differences in the mean and standard deviation of the inter-tap interval between pacing conditions. For the 1,000 and 5,000 ms tasks, there were significant differences in the mean inter-tap interval following auditory pacing compared with self-pacing. For the 2,000 ms syncopation condition and 5,000 ms task, there were significant differences from self-pacing in the standard deviation of the inter-tap interval following auditory pacing. [Conclusion] These results suggest that the accuracy of periodic movement with intervals of 1,000 and 5,000 ms can be improved by the use of auditory pacing. However, the consistency of periodic movement is mainly dependent on the inherent skill of the individual; thus, improvement of consistency based on pacing is unlikely.

Repeated paced mating promotes the arrival of more newborn neurons in the main and accessory olfactory bulbs of adult female rats

We have previously shown that the first-paced mating encounter increases the number of newborn cells in the granule cell layer (Gra; also known as internal cell layer, ICL) of the accessory olfactory bulb (AOB) in the adult female rat (Corona et al., 2011). In the present study we evaluated if repetition of the stimulus (paced mating) could increase the arrival of more newborn neurons in the olfactory bulb generated during the first session of paced sexual contact. Sexually naive female rats were bilaterally ovariectomized, hormonally supplemented with estradiol (E2) and progesterone (P) and randomly assigned to one of four groups: (1) without sexual contact, (2) one session of paced mating, (3) four sessions of paced mating, and (4) four sessions of non-paced mating. We also included a group of gonadally intact females. On the first day of the experiment, all females were i.p. injected with the marker of DNA synthesis bromodeoxyuridine and were killed 16 days later. Blood was collected at sacrifice to determine the plasma levels of E2 and P. The number of newborn neurons that arrived at the ICL of the AOB and the Gra of the main olfactory bulb (MOB) increased, relative to all other groups, only in the group that repeatedly mated under pacing conditions. No differences were found in E2 and P levels between supplemented groups indicating that our results are not influenced by changes in hormone concentrations. We suggest that repeated paced mating promotes the arrival of more newborn neurons in the AOB and MOB.