Stable Rhythm Research Articles

Mathematical model for frequency modulation in the respiratory network

Neuromodulators, such as amines and neuropeptides, alter the activity of neurons and neuronal networks. In this work, we investigate how neuromodulators which activate G-proteins and second messenger systems can modulate the frequency of bursting neurons in a critical portion of the respiratory neural network, the pre-Botzinger complex (pBC). Inspiratory neurons in the pBC produce a regular bursting rhythm in phase with the activity of inspiratory muscles in the diaphragm. These neurons are a vital part of the ponto-medullary neuronal network, which generates a stable respiratory rhythm [1]. The frequency of pBC depends on the concentration of Serotonin (5-HT) and Substance P (SP), neurotransmitters released by the nearby Raphe nucleus. Both neurotransmitters, 5-HT and SP, affect pBC neurons by activating receptors coupled with the Gq protein pathway, thereby inducing Ca2+ release from the Endoplasmic Reticulum (ER). We have previously developed a mathematical model of the pBC neuron, which incorporates explicit activation of Gq-protein coupled receptors, and have shown that activation of these receptors can result in Ca2+ oscillations in the dendritic compartment [2]. The model exhibits two independent bursting mechanisms – bursting in the soma depends on persistent sodium current, whereas bursting in the dendrite follows Ca2+ oscillations. It has been recently found that the connection between the pBC and the Raphe nucleus is bi-directional: not only does the Raphe nucleus release 5-HT and SP to modulate the frequency of pBC neurons, but also the rhythmic activity in the pBC increases the firing of Raphe neurons [3]. In this work, we extend our model to a network of pBC neurons while incorporating this newly discovered interaction between Raphe and pBC nuclei. Using a simulated 50-cell network of excitatory connected pBC neurons with a heterogeneous distribution of persistent sodium conductance and ER Ca2+, we show that a tonic release of neurotransmitters acting on the Gq protein pathway increases the number of intrinsic bursters in such a network. However, when we simulated the application of different concentrations of SP or 5-HT, there was no dose-dependent frequency modulation. We then added a positive feedback between the Raphe excitability and pBC activity, representing the release of neurotransmitters from Raphe, and found that this feedback induces frequency modulation the pBC neurons (Figure ​(Figure1).1). Thus, our model shows that the frequency of the respiratory rhythm can be modulated via phasic release of 5-HT and SP from the Raphe nucleus. Figure 1 Inspiratory frequency modulation of pBC by excitatory neurotransmitters, which act on Gq-coupled receptor. [NT] represents neurotransmitter concentration. (A-C) Example of raster plots for three different neurotransmitter concentrations. (A) Rhythmic ...

Neurologic Recovery Following Prolonged Out-of-Hospital Cardiac Arrest With Resuscitation Guided by Continuous Capnography

A 54-year-old man with no known cardiac disease collapsed outdoors in a small rural community. The cardiac arrest was witnessed, and immediate cardiopulmonary resuscitation was begun by a bystander and a trained first responder who was nearby. The patient was moved into a building across the street for continued resuscitation. First responders arrived with an automated external defibrillator, and ventricular fibrillation was documented. First responders delivered 6 defibrillation shocks, 4 of which transiently restored an organized electrocardiographic rhythm but with no pulse at any time. Additional emergency medical services personnel from nearby communities and an advanced life support (ALS) flight crew arrived. The flight crew initiated ALS care. The trachea was intubated, ventilation controlled, and end-tidal carbon dioxide tension continuously monitored. Antiarrhythmic and inotropic drugs were administered intravenously. An additional 6 shocks were delivered using the ALS defibrillator. End-tidal carbon dioxide measurements confirmed good pulmonary blood flow with chest compressions, and resuscitation was continued until a stable cardiac rhythm was restored after 96 minutes of pulselessness. The patient was transported by helicopter to the hospital. He was in cardiogenic shock but maintained a spontaneous circulation. Coronary angiography confirmed a left anterior descending coronary artery thrombotic occlusion that was treated successfully. After hospital admission, the patient required circulatory and ventilatory support and hemodialysis for acute renal failure. He experienced a complete neurologic recovery to his pre-cardiac arrest state. To our knowledge, this is the longest duration of pulselessness in an out-of-hospital arrest with a good outcome. Good pulmonary blood flow was documented throughout by end-tidal carbon dioxide measurements.

Effect of rotating shift work on childbearing and birth weight: a study of women working in a semiconductor manufacturing factory

Stable circadian rhythm is important for both maternal and fetal health. This retrospective analysis of women in a semiconductor factory evaluated the effect of shift work exposure on childbearing and birth weight. Records of 440 female employees (initial mean age: 28.4 years) including 111 mothers who had 158 live births during the period of observation (1997-2007) were reviewed. The data analyzed included maternal age, general health condition, highest educational level, life-style and occupational factors, as well as newborn gender, birth weight, birth order and gestational age. The childbearing rates of female workers on three different work schedules (consistent daytime work (CDW), intermittent (i-) or persistent (p-) rotating shift works (RSW)) were 32.1%, 20.0% and 25.4%, respectively (P=0.047). After controlling for potential confounding factors, childbearing rates among women with CDW exceeded those of shift workers (odds ratio (OR), 1.7; 95% confidence interval (CI), 1.0-3.0). The birth weights of newborns from mothers on the three work schedules (CDW, i-RSW and p-RSW) were significantly different (3271.7±395.4, 3251.3±460.9, and 2998.5±381.2 g, respectively (P<0.01). Newborns within the lightest birth weight quintile were significantly more likely to be born to mothers with exposure to p-RSW (OR, 4.3; 95% CI, 1.1-16.8). Rotating shift work exposure was significantly associated with decreased childbearing and lighter birth weight in women working in this semiconductor manufacturing factory. Work schedules should be carefully planned for female employees who are pregnant or preparing for pregnancy. Prenatal evaluations for mothers with persistent day-night rotating shift work exposures are especially necessary.

Catheter Ablation of Electrical Storm in a Collaborative Hospital Network

An electrical storm (ES) is defined as multiple ventricular arrhythmia episodes leading to implantable cardioverter defibrillator interventions. Although conventional rhythm stabilization might be of help acutely, ES involves high mortality and morbidity. We evaluated the effect of catheter ablation strategies in the setting of an interhospital collaborative network on the recurrence of ventricular arrhythmia episodes and mortality in patients with ES. Consecutive patients presenting for invasive treatment of ES from December 2007 to December 2009 were included. All patients underwent catheter ablation of ventricular arrhythmia. The strategies were adapted to the individual cardiac pathologic features. The follow-up examination constituted periodic implantable cardioverter defibrillator interrogation. A total of 32 patients were included. Of the 32 patients, 29 (91%) had monomorphic ventricular tachycardia and 3 ventricular fibrillation. The mean number of implantable cardioverter defibrillator-treated episodes within 7 days before ablation was 16 ± 11. Of the 32 patients, 27 underwent ablation within 24 hours after admission, and 5 underwent acute ablation within 8 hours. In 3 patients, epicardial ablation was performed. In all but 2 patients (6%), the clinical arrhythmia was successfully ablated. During a median follow-up of 15 months, 10 patients (31%) had recurrences of sustained ventricular arrhythmia, including 2 patients (6%) with recurrent ES. Three patients (9%) died during the follow-up period. In conclusion, catheter ablation effectively suppressed ventricular arrhythmia midterm recurrences in patients presenting with ES. Catheter ablation is complex in these severely sick patients. The recurrence rate of ventricular arrhythmia appears to be 31% and the mortality rate to be 9%. Collaborative hospital networks to increase the prompt availability of ES ablation might help to optimize the ES outcome.

Stable production rhythms across languages for bilingual speakers.

There has been a great deal of work on classifying spoken languages according to their perceived or acoustically‐measured rhythmic structures. The current study examined the speech of 12 Spanish‐English bilinguals producing sentences in both languages using rhythmic measures based on the amplitude envelopes extracted from different frequency regions—the envelope modulation spectrum (EMS). Using discriminant factor analysis, EMS variables demonstrated a moderate ability to classify the language being spoken suggesting that rhythmic differences between languages survive even when speaker is controlled. More interesting is the fact that EMS variables could reliably classify which speaker produced each sentence even across languages. This result suggests that there are stable rhythmic structures in an individual talker’s speech that are apparent above and beyond the structural constraints of the language spoken. The EMS appears capable of describing systematic characteristics of both the talker and the language spoken. [Work supported by NIH‐NIDCD].

The Robust Ticking of a Circadian Clock

Many organisms use circadian clocks to anticipate changes between day and night. It had long been believed that these clocks are driven primarily by transcription translation cycles (TTCs) built on negative feedback on gene expression. However, while circadian clocks can maintain robust rhythms for years in the absence of any daily cue, recent experiments have vividly demonstrated that gene expression is often highly stochastic. This raises the question of how these clocks can be so robust against biochemical noise. In multicellular organisms, the robustness might be explained by intercellular interactions, but it is now known that even unicellular organisms can have very stable circadian rhythms. The clock of the cyanobacterium S. elongatus, for example, has a correlation time of several months, even though the clocks of the different cells in a population hardly interact with one another. How circadian clocks can be so stable even at the single cell level is not understood. Interestingly, it has recently been discovered that the S. elongatus clock also includes a protein phosphorylation cycle (PPC) that can run independently of the transcription-translation cycle (TTC). Here, we use mathematical modeling to study how these two clocks interact in growing, dividing cells. We find that a clock built on a PPC alone is highly stable when protein turnover is low. For high protein turnover rates, however, a PPC becomes unstable; indeed, at high growth rates, when protein turnover is necessarily high, a TTC becomes indispensable for the PPC to function. On the other hand, a clock based on a TTC alone functions only when the protein turnover rate is large; it fails dramatically at low growth rates in the absence of active protein degradation. The power of coupling a PPC to a TTC is that the clock becomes robust over the full range of growth conditions. Importantly, the TTC and the PPC in S. elongatus are much more tightly intertwined than conventional coupled phase oscillators; as a result, particularly for intermediate growth rates, the combination of the two far outperforms not just each of its two components individually, but also a hypothetical system in which the two parts are coupled in normal textbook fashion.

Unexpected pacing inhibition upon exposure to the 3T static magnetic field prior to imaging acquisition: What is the mechanism?

A 62-year-old man with an implantable cardioverter-defibrillator (ICD) and a history of lung cancer developed severe headaches. During performance of cranial 3T (Signa Excite-HD, General Electric, Waukesha, WI, USA) magnetic resonance imaging (MRI), the patient was monitored with both ECG and pulse oximetry. 1 Gimbel J.R. Magnetic resonance imaging of implantable cardiac rhythm devices at 3.0 tesla. Pacing Clin Electrophysiol. 2008; 31: 795-801 Crossref PubMed Scopus (73) Google Scholar The patient's hemodynamically stable underlying rhythm was sinus at 40 to 45 bpm with a narrow QRS and normal PR interval (Figure 1A). The pre-MRI programming strategy chosen for the patient's St. Jude Medical (Sylmar, CA, USA) Atlas II+ DR V-238 (A-lead: St. Jude Medical 1388TC-52 cm; V-lead: Medtronic [Mounds View, MN, USA] 6947-58 cm) was all tachycardia therapies “off”, AAI pacing at 70 ppm, and nominal sensitivities. The patient's paced rhythm through the programmer just prior to the patient being placed on the table in the MRI suite is shown in Figure 1B.

Bifurcation analysis of bursting solutions of two Hindmarsh-Rose neurons with joint electrical and synaptic coupling

In this paper, we investigate the dynamic behavior of a system of two coupled Hindmarsh-Rose (HR) neurons, based on bifurcation analysis of its fast subsystem. The individual HR neuron has chaotic behavior, but they can become regularized when coupled through synaptic coupling or joint electrical-synaptic coupling. Through numerical methods we first investigate the bifurcation structure of its fast subsystem. We show that the emerging of periodic patterns of neurons is related to topological changes of its underlying bifurcations. The Lyaponov exponent calculations further reveal the pathway from chaotic bursting behavior to regular bursting of HR neurons. Finally, we include both electrical and synaptic coupling in the system, and numerically calculate the time dynamics. Even though electrical couplings (or gap junctions) usually does not regularize chaotic trajectories, but joint coupling has been more effective than synaptic coupling alone in producing stable rhythms. The main contribution of this paper is that we provide a mathematical description for transitions of neuron dynamics from chaotic trajectories to regular bursting when synaptic and electrical-synaptic coupling strengthens, using bifurcation analysis.

Robust circadian clocks from coupled protein-modification and transcription–translation cycles

The cyanobacterium Synechococcus elongatus uses both a protein phosphorylation cycle and a transcription-translation cycle to generate circadian rhythms that are highly robust against biochemical noise. We use stochastic simulations to analyze how these cycles interact to generate stable rhythms in growing, dividing cells. We find that a protein phosphorylation cycle by itself is robust when protein turnover is low. For high decay or dilution rates (and compensating synthesis rates), however, the phosphorylation-based oscillator loses its integrity. Circadian rhythms thus cannot be generated with a phosphorylation cycle alone when the growth rate, and consequently the rate of protein dilution, is high enough; in practice, a purely posttranslational clock ceases to function well when the cell doubling time drops below the 24-h clock period. At higher growth rates, a transcription-translation cycle becomes essential for generating robust circadian rhythms. Interestingly, although a transcription-translation cycle is necessary to sustain a phosphorylation cycle at high growth rates, a phosphorylation cycle can dramatically enhance the robustness of a transcription-translation cycle at lower protein decay or dilution rates. In fact, the full oscillator built from these two tightly intertwined cycles far outperforms not just each of its two components individually, but also a hypothetical system in which the two parts are coupled as in textbook models of coupled phase oscillators. Our analysis thus predicts that both cycles are required to generate robust circadian rhythms over the full range of growth conditions.

Human Metapneumovirus Subgroup Changes and Seasonality During Epidemics

Human metapneumovirus (HMPV) is a major cause of respiratory tract illness in young children and causes annual outbreaks in winter and spring seasons. We evaluated the subgroups of HMPV that caused annual outbreaks and its seasonal occurrence during a 21-year period. Real-time PCR was used for detection of HMPV in 3576 nasopharyngeal aspirates that had been continuously collected year-round for the years 1987 to 2008 from infants hospitalized with acute respiratory tract illness. Phylogenetic analysis was used to assess HMPV subgroups. Of the 3576 samples obtained, 202 (5.6%) tested positive for HMPV. All known HMPV subgroups (A1, A2a, A2b, B1, B2) could be identified as important respiratory tract pathogens in infants. We found that one HMPV subgroup predominated each year, and it was displaced by another subgroup every 1 to 3 years. Besides the frequent change in predominant HMPV subgroups, we observed a yearly shift in the seasonal occurrence, with a strong peak of HMPV activity in late spring-summer months every second year. HMPV activity is characterized by a periodic change in the predominant subgroup and it shows a stable seasonal rhythm of alternating winter and spring activity.

An NMDA antagonist inhibits light but not GRP-induced phase shifts when administered after the phase-shifting stimulus

Brief light pulses or microinjection of gastrin-releasing peptide (GRP) into the third ventricle or near the suprachiasmatic nucleus (SCN) induce phase shifts of circadian rhythms during the subjective night. It has previously been reported that these effects are strongly influenced by the activation of N-methyl- d-aspartate (NMDA) receptors and the availability of glutamate. We hypothesized that the photic signaling pathway in the SCN was dependent on glutamate neurotransmission even after the completion of a photic stimulus. Adult male Syrian hamsters equipped with a surgically implanted guide cannula aimed at the SCN region were housed in constant darkness until stable free-running rhythms of wheel-running activity were apparent. Light pulses administered in the early night induced phase delays of circadian rhythms which were attenuated by the co-administration of (±)-2-amino-5-phosphonopentanoic acid (AP5), an NMDA antagonist. Microinjection of AP5 also inhibited light-induced shifts, to a lesser extent, immediately after and 15 min after, but not 30 min after the light pulse. A second experiment was designed to test whether AP5 would be able to attenuate GRP-induced shifts 15 min following microinjection of GRP. Phase shifts of animals that received microinjection of AP5 15 min after the administration of GRP were not different from those that received microinjection of GRP and vehicle. These data suggest that glutamate signaling remains necessary for a full photic response in the SCN even after the termination of the photic signal, but that this dependency ends once GRP-dependent signaling is complete.

Low-dose coronary computed tomography angiography using prospective ECG-triggering compared to invasive coronary angiography

To assess the diagnostic accuracy of prospective ECG-triggering 64-slice multidetector computed tomography (MDCT) coronary angiography for evaluation of coronary artery disease (CAD). Forty-two patients (31 males, 11 females, mean age 64 years) underwent cardiac CT and invasive coronary angiography (ICA). Patients with a heart rate of <65 beats/min with stable heart rhythm were included in the study sample. We used a prospective ECG-triggering protocol. Luminal narrowing over 50% was considered to be significant according to a modified 17-segment AHA model, using invasive coronary angiography (ICA) as the standard of reference. The mean radiation dose was 3.5 mSv ± 0.3 (range, 3.3-4.2 mSv), and 542 of 549 segments (98.7%) in the 42 patients were diagnostic. In contrast, 119 of 542 segments (22%) were diagnosed as significant by ICA. The sensitivity, specificity, accuracy, PPV and NPV were 95.0, 96.2, 96, 85.8 and 98.8%, respectively. False positive results were affected by densely calcified plaques, whereas false negatives were caused by motion artifact with poor vessel attenuation at the distal segments or near the bifurcation area of the coronary arteries. Prospective ECG-triggering MDCT is a useful method for evaluating CAD in patients with a lower heart rate with low radiation dose.

Asymptomatic Sustained Ventricular Fibrillation in a Patient With Left Ventricular Assist Device

Optimal medical treatment, cardiac resynchronization, and the use of an implantable cardioverter defibrillator are established therapies of severe congestive heart failure. In refractory cases, left ventricular assist devices are more and more used not only as bridging to cardiac transplantation but also as destination therapy. Ventricular arrhythmias may represent a life-threatening condition and often result in clinical deterioration in patients with congestive heart failure. We report a case of asymptomatic sustained ventricular fibrillation with preserved hemodynamics caused by a nonpulsatile left ventricular assist device. Consecutive adequate but unsuccessful discharges of the implantable cardioverter defibrillator were the only sign of the usually fatal arrhythmia, prompting the patient to consult emergency services. Electrolyte supplementation and initiation of therapy with amiodarone followed by external defibrillation resulted in successful restoration of a stable cardiac rhythm after 3.5 hours.

A dynamical systems analysis of afferent control in a neuro--mechanical model of locomotion

Existing models have represented a locomotor system as a rhythmic driver, or central pattern generator (CPG), coupled to a mechanical limb, with feedback closing the loop. Our collaborators have developed a version of this model in which the CPG establishes a rhythm when activating drive is present, and feedback from ground strike helps control phase switching and rhythm stabilization. Spinal cord injury can be simulated through termination of drive, which ceases the rhythm. We derive and analyze a reduced representation of this model, which will elucidate general principles of phase and frequency control in normal locomotion. We aim to understand how the presence of feedback provides stable locomotion, allowing oscillations at a wider range of drive values to the CPG (specifically at lower values) than the CPG without afferent feedback. Furthermore, increasing the drive intensity to the CPG increases locomotor speed by reducing only the duration of the stance phase, at a relatively constant duration of swing phase [1]. This phase asymmetry has been seen in normal locomotion in cats, rats, and humans, but is not observed in the locomotor model without feedback, so we analyze how feedback facilitates this asymmetry. We will also reveal sufficient conditions for recovering rhythmicity in the injured state - how in the absence of drive, increased feedback can restore locomotion and contribute to locomotor stability, with an analysis of differences in rhythm robustness before and after loss of drive.

Computational model explaining two types of bursting found in inspiratory pacemakers.

The respiratory rhythm is generated within the network of inspiratory neurons in the pre-Botzinger complex (pBC) and persists under highly variable neuronal input. The mechanism of pBC rhythm generation at the level of the network is an active area of debate and inquiry. A fraction of these inspiratory pBC neurons generate a stable bursting rhythm even when pharmacologically isolated from the network and likely contribute to the rhythm. Experiments indicate that the intrinsic bursting mechanism of these pacemaker neurons depends on either persistent sodium current or changes in intracellular Ca2+. Motivated by experimental evidence obtained from these subpopulations of bursting neurons, we developed a two-compartment mathematical model of a pBC pacemaker neuron with two independent bursting mechanisms. The model explains a number of contradictory experimental results and is able to generate a robust bursting rhythm over a large range of parameters, with a frequency adjusted by neuromodulators. For the somatic compartment of our model, we used a previously developed model of pBC pacemaker neurons [1]. In this model, action potentials are generated by a fast sodium current (INa) and a delayed rectifier potassium current (IK), and the burst is terminated by slow inactivation of a persistent sodium current (INaP). The bursting in the dendritic compartment of our model follows the Ca2+ oscillations arising from periodic Ca2+ release from intracellular stores. Briefly, the activation of a Gq-protein cascade leads to an increase in the concentration of IP3, which binds to its receptor on the surface of the endoplasmic reticulum and initiates Ca2+ influx into the cytosol. A calcium-activated nonspecific cation current (ICaN) then depolarizes the cell membrane in response to the increase in intracellular Ca2+ concentration. This depolarizing potential spreads to the soma and activates action potential-generating currents (INa and IK), thus initiating the burst. Finally, the action potential propagates to the dendrite, producing a dendritic burst of smaller amplitude. The model predicts that in synaptically isolated cells, the bursting mechanism depends on neuromodulators, endogenously released within the pBC. The neuromodulatory tone can bias the neuron to a somatic (INaP) or dendritic (Ca2+ and ICaN) mode of bursting, or a hybrid of the two. In the dendritic mode, the period of bursting is largely modulated by the IP3 concentration, whereas in the somatic mode the burst duration is modulated by the persistent sodium current. This model displays changes in burst duration and period that are consistent with experimentally published pharmacological manipulations, such as the application of ion channel blockers (FFA and Riluzole) as well as neuromodulatory manipulations.

Effects of repeated surgical stress on daily changes of body core temperature in mice

Daily body core temperature rhythm has been known to become blunted for several days following intra-abdominal implantation of biotelemetry transmitters in small rodents and about a week is required for re-establishment of stable body core temperature oscillation. In the present study carried out on mice it was found that a repetition of the same minor surgical intervention (laparotomy) several days apart could speed up the stabilization of body temperature oscillations. Melatonin supplied with the drinking water continuously was found to speed up the return of stable daily body temperature rhythm further on consecutive laparotomies, while daily injections of methylprednisolone resulted in some delay in the development of stable body core temperature oscillations. It is concluded that in C57BL/6 mice possessing low plasma levels of melatonin exhibit an adaptive response to repeated stresses influencing the dynamics of daily body temperature rhythm.

Just How Stable Are Escape Rhythms after Atrioventricular Junction Ablation?

Atrioventricular (AV) node ablation with implantation of a permanent pacemaker is an established mode of therapy in the treatment of atrial fibrillation. However, concern exists regarding subsequent dependency on an entirely paced rhythm and the possible sequela of unheralded pacemaker failure. Data regarding escape rhythm lability, an important feature of pacemaker dependency, are limited. The purpose of this study was twofold: (1) to determine the characteristics of escape rhythms at predefined serial time intervals following AV node ablation and pacemaker implantation, and (2) to identify risk factors predictive of unstable escape rhythms. Patients undergoing AV node ablation and pacemaker implantation were assessed for the presence or absence of an escape rhythm during pacemaker interrogation at five predetermined serial time points. Baseline demographics and comorbid conditions were evaluated as potential predictors of those with labile escape rhythms. Seventy-nine percent of the 96 patients studied had an underlying escape rhythm (> or =30 beats per minute) immediately postablation. Although the percentage of patients with an escape rhythm increased at each follow-up interval, the number of patients who consistently demonstrated an escape rhythm declined with each follow-up, with 28% of patients lacking an escape rhythm at some time point, i.e., labile escape rhythm. There were no significant predictors of a labile escape rhythm. Among patients who have undergone AV node ablation and pacemaker implantation, 72% have a stable escape rhythm over time, but others are at risk for pacemaker dependency, as predicted by an underlying absent or labile escape rhythm.

Circadian and ultradian rhythms in locomotory activity of inbred strains of mice

In this study we recorded locomotor activity of two inbred of mice (B6 and C) in two photoperiod conditions (LD 12:12 and DD) to characterize behavioural parameters of the endogenous rhythms of locomotor activity with particular attention to the ultradian rhythms. Literature reveals discordant data for these parameters, both for animals belonging to the same strain and to those in the same laboratory or monitored in the same conditions. Our results show that C strain has a shorter and unstable endogenous circadian period, while B6 strain has a longer and stable endogenous rhythm. In our study, B6 showed a longer and stable period than C, so we can confirm the presence of a genetic component underlying this trait. Ultradian rhythms are expressed independently of either the photoperiod or the circadian rhythm. There are no strain-dependent differences in the periods of 12, 8 and 4 h. The situation was different for the length of the ultradian period in the range 1–8 h and for the weighted power in the ranges 480–300 and 300–100 min, for which there were differences between photoperiods and strains.

Daily locomotor activity in five domestic animals

Abstract The aim of this study was to compare locomotor activity in five domestic animals. Five female Comisana sheep, five female Maltese goats, five female Bruna cows, and five female Thoroughbred horses were housed separately in a soundproof box equipped with an airflow system and five female Blue Vienna rabbits were individually housed in metallic cages. Animals were kept under a 12/12 Light/Dark cycle and indoor ambient temperature (16-20°C). To record activity, an Actiwatch-Mini® was placed on each animal by means of a collar. Analysis by the cosinor procedure indicated a daily rhythm of locomotor activity in each of the five species studied. The main activity was observed during the photophase in sheep, goats, cows and horses, and during the scotophase in rabbits. The comparison among the species studied underlined a stable daily rhythm of locomotor activity in cows and horses, while sheep, goats and rabbits showed a weak daily rhythm of locomotor activity.

Rest-Activity Patterns in Institutionalized Korean Older Adults with Dementia: A Pilot Study

This pilot study examined rest-activity patterns and related factors in institutionalized older adults with dementia in Korea. Twelve individuals, residing in either a nursing home or an assisted living facility, participated in the study. Actigraphic measurements were collected for seven consecutive 24-hour periods to assess rest-activity patterns. The participants' demographic characteristics, cognitive function, problematic behaviors, and light exposure were also assessed. The results indicated the participants experienced sleep disturbances, including multiple awakenings at night and excessive daytime napping. Those in the nursing home had significantly more interdaily stability and less intradaily variability, with higher relative amplitude in their rest-activity rhythms, indicating more stable and stronger rest-activity rhythms than those in the assisted living facility. These findings emphasize the importance of the institutional environment in care planning to improve sleep and rest-activity rhythm for older adults with dementia.