Sympathetic Oscillations Research Articles

Spectral analysis of cardiovascular oscillations in the 7-day regimen of losartan administration with and without cold stress.

Spectral analysis of heart rate (HR) and blood pressure (BP) variabilities (BPV and HRV) is widely available and utilized in understanding the dynamic cardiovascular autonomic regulation in a variety of pathophysiological conditions. In conscious cold-stressed (CS) rats, we examined the effect of a 7-day regimen administration of losartan, a selective nonpeptide angiotensin AT1 receptor blockade, on BPV and HRV at three frequency components: very-low frequency (VLF), low frequency (LF), and high frequency (HF). Key findings in changes of systolic BP (SBP), HR, and spectral power densities for cardiopulmonary oscillations (HF), sympathetic oscillations (LF), cardiovascular myogenic oscillations (VLF), and overall autonomic activity total power (TP) showed: (I) In the resting PreCS trial, compared with the saline, losartan increased HFBPV, TPHRV, all three HRV frequency powers, and the occurrence of the dicrotic notch (DN). However, it decreased SBP, HR, and the LFBPV frequency power. (II) In the CS trial, losartan significantly decreased SBP and DN occurrence and HR and LF/HFHRV but significantly increased HFHRV, TPBPV, and all three BPV frequency powers. In addition, similar to the saline, losartan showed positively correlated LFBPV and VLFBPV. Conversely, losartan converted the original inverse correlations between LFHRV and LFBPV of CS to a positive correlation. (III) Compared with saline in PreCS and CS trials, losartan detached the corresponding sympathetic oscillations between LFBPV and LFHRV. The overall result indicates that endogenous angiotensin II, through stimulation of the AT1 receptor, augments sympathetic tone but attenuates sympathetic oscillations in rats, particularly under the stressful cooling impacts.

ConvNets for counting: Object detection of transient phenomena in steelpan drums

We train an object detector built from convolutional neural networks to count interference fringes in elliptical antinode regions in frames of high-speed video recordings of transient oscillations in Caribbean steelpan drums, illuminated by electronic speckle pattern interferometry (ESPI). The annotations provided by our model aim to contribute to the understanding of time-dependent behavior in such drums by tracking the development of sympathetic vibration modes. The system is trained on a dataset of crowdsourced human-annotated images obtained from the Zooniverse Steelpan Vibrations Project. Due to the small number of human-annotated images and the ambiguity of the annotation task, we also evaluate the model on a large corpus of synthetic images whereby the properties have been matched to the real images by style transfer using a Generative Adversarial Network. Applying the model to thousands of unlabeled video frames, we measure oscillations consistent with audio recordings of these drum strikes. One unanticipated result is that sympathetic oscillations of higher-octave notes significantly precede the rise in sound intensity of the corresponding second harmonic tones; the mechanism responsible for this remains unidentified. This paper primarily concerns the development of the predictive model; further exploration of the steelpan images and deeper physical insights await its further application.

Transient oscillations in steelpan drums tracked via machine learning

Applying a machine learning based object detector to high-speed videos of Caribbean steelpan drums illuminated by laser electronic speckle pattern interferometry (ESPI), we can track the development of sympathetic vibrations in response to drum strikes. This object detector was trained on a dataset of crowdsourced human-annotated images obtained in the Steelpan Vibrations Project on the Zooniverse platform. When the model is used to supply annotations to thousands of unlabeled video frames, we measure visual oscillations at frequencies consistent with audio recordings of these drum strikes. In this talk we share early physics results such as the unanticipated phenomenon of sympathetic oscillations of higher-octave notes that significantly precede the rise in sound intensity of the corresponding second harmonic tones; the mechanism responsible for this remains unidentified.

Mechanisms Contributing to the Generation of Mayer Waves.

Mayer waves may synchronize overlapping propriobulbar interneuronal microcircuits constituting the respiratory rhythm and pattern generator, sympathetic oscillators, and cardiac vagal preganglionic neurons. Initially described by Sir Sigmund Mayer in the year 1876 in the arterial pressure waveform of anesthetized rabbits, authors have since extensively observed these oscillations in recordings of hemodynamic variables, including arterial pressure waveform, peripheral resistance, and blood flow. Authors would later reveal the presence of these oscillations in sympathetic neural efferent discharge and brainstem and spinal zones corresponding with sympathetic oscillators. Mayer wave central tendency proves highly consistent within, though the specific frequency band varies extensively across, species. Striking resemblance of the Mayer wave central tendency to the species-specific baroreflex resonant frequency has led the majority of investigators to comfortably presume, and generate computational models premised upon, a baroreflex origin of these oscillations. Empirical interrogation of this conjecture has generated variable results and derivative interpretations. Sinoaortic denervation and effector sympathectomy variably reduces or abolishes spectral power contained within the Mayer wave frequency band. Refractorines of Mayer wave generation to barodeafferentation lends credence to the hypothesis these waves are chiefly generated by brainstem propriobulbar and spinal cord propriospinal interneuronal microcircuit oscillators and likely modulated by the baroreflex. The presence of these waves in unitary discharge of medullary lateral tegmental field and rostral ventrolateral medullary neurons (contemporaneously exhibiting fast sympathetic rhythms [2–6 and 10 Hz bands]) in spectral variability in vagotomized pentobarbital-anesthetized and unanesthetized midcollicular (i.e., intercollicular) decerebrate cats supports genesis of Mayer waves by supraspinal sympathetic microcircuit oscillators. Persistence of these waves following high cervical transection in vagotomized unanesthetized midcollicular decerebrate cats would seem to suggest spinal sympathetic microcircuit oscillators generate these waves. The widespread presence of Mayer waves in brainstem sympathetic-related and non-sympathetic-related cells would seem to betray a general tendency of neurons to oscillate at this frequency. We have thus presented an extensive and, hopefully cohesive, discourse evaluating, and evolving the interpretive consideration of, evidence seeking to illumine our understanding of origins of, and insight into mechanisms contributing to, the genesis of Mayer waves. We have predicated our arguments and conjectures in the substance and matter of empirical data, though we have occasionally waxed philosophical beyond these traditional confines in suggesting interpretations exceeding these limits. We believe our synthesis and interpretation of the relevant literature will fruitfully inspire future studies from the perspective of a more intimate appreciation and conceptualization of network mechanisms generating oscillatory variability in neuronal and neural outputs. Our evaluation of Mayer waves informs a novel set of disciplines we term quantum neurophysics extendable to describing subatomic reality. Beyond informing our appreciation of mechanisms generating sympathetic oscillations, Mayer waves may constitute an intrinsic property of neurons extant throughout the cerebrum, brainstem, and spinal cord or reflect an emergent property of interactions between arteriogenic and neuronal oscillations.

Midbrain control of breathing and blood pressure: The role of periaqueductal gray matter and mesencephalic collicular neuronal microcircuit oscillators.

Neural circuitry residing within the medullary ventral respiratory column nuclei and dorsal respiratory group interact with the Kölliker-Fuse and medial parabrachial nuclei to generate the corebreathing rhythm and patternduring resting conditions. Triphasic eupnea consists of inspiratory [I], post-inspiratory [post-I], and late-expiratory [E2] phases. Mesencephalic zones exert modulatory influences upon respiratory rhythm-generating circuitry, sympathetic oscillators, and parasympathetic nuclei. The earliest evidence supporting the existence of midbrain control of breathing derives from studies conducted by Martin and Booker in 1878. These authors demonstrated electrical stimulation of the deep layers of themesencephalic colliculi in the rabbitaugmented ventilation and sequentially elicited chest wall tremors and tetany. Investigations performed during the past several decadeswould demonstrate stimlation of distributed zones within the midbrain reticular formation elicits starkly disparate effects upon respiratory phase switching. Schmid, Böhmer, and Fallert demonstrated electrical stimulation of the nucleus rubreand emanating axon bundles alternately elicits or inhibits the activity of medullary expiratory- or inspiratory-related units and phrenic nerve discharge with differential latency. A series of studies would later indicate the red nucleus mediates hypoxic ventilatory depression. Periaqueductal gray matter neurons exhibit extensive afferent and efferent interconnectivity with suprabulbar, brainstem, and spinal cord zones aptly positioning these units to modulate breathing, autonomic outflow, nociception locomotion, micturtion, and sexual behavior.Experimental stimulatory activation of the tectal colliculi and periaqueductal gray matter via electrical current or glutamate, D,L-homocysteinic acid, or bicuculline microinjections coordinately modulates neuromotor inspiratory bursting frequency and amplitude and discharge of pre-Bötzinger complex, ventrolateral medullary late-I and post-I, and ventrolateral nucleus tractus solitarius decrementing early-I and augmenting and decrementing late-I neurons, elicits expiratory outflow and vocalization, and blunt the Hering-Breuer reflex in unanesthetzed decerebrate and anesthetized preprations of the cat and rat. Stimulation of the mesencephalic colliuli or dorsal divisions of the PAG potently amplifes renal sympathetic neural efferent activity, dynamic arterial pressure magnitude, and myocardial contraction frequency and elicits various behavioral defense responses. Elicited physiological effects exhibit extensive locoregional heterogeneity and variably enlist requisite contributions from the dorsomedial hypothalamus and/or lateral parabrachial nuclei. Stimulation of the dorsal mesencephalon occasionally elicits dynamic increases of arterial pressure magnitude exhibiting prominent oscillatory variability coherent with phrenic nerve discharge, perhaps by generating intra-neuraxial hysteresis, serving to intermittently deliver blood to organ vascular beds under high pressure in order to prevent organ edema, microcirculatory dysfunction, and downregulation of vascular smooth muscle alpha adrenergic receptors. Chemosensitive mesencephalic caudal raphéunits and projections of hypoxia-sensitive units in the caudal hypothalamus to the periaqueductal gray matter may imply the existence of a diencephalo-smesencephalic chemosensitive network modulating breathing and sympathetic discharge.

Low-Frequency Oscillations in Cardiac Sympathetic Neuronal Activity.

Sudden cardiac death caused by ventricular arrhythmias is among the leading causes of mortality, with approximately half of all deaths attributed to heart disease worldwide. Periodic repolarization dynamics (PRD) is a novel marker of repolarization instability and strong predictor of death in patients post-myocardial infarction that is believed to occur in association with low-frequency oscillations in sympathetic nerve activity. However, this hypothesis is based on associations of PRD with indices of sympathetic activity that are not directly linked to cardiac function, such as muscle vasoconstrictor activity and the variability of cardiovascular autospectra. In this review article, we critically evaluate existing scientific evidence obtained primarily in experimental animal models, with the aim of identifying the neuronal networks responsible for the generation of low-frequency sympathetic rhythms along the neurocardiac axis. We discuss the functional significance of rhythmic sympathetic activity on neurotransmission efficacy and explore its role in the pathogenesis of ventricular repolarization instability. Most importantly, we discuss important gaps in our knowledge that require further investigation in order to confirm the hypothesis that low frequency cardiac sympathetic oscillations play a causative role in the generation of PRD.

Mechanisms underlying the generation of autonomorespiratory coupling amongst the respiratory central pattern generator, sympathetic oscillators, and cardiovagal premotoneurons.

The respiratory rhythm and pattern and sympathetic and parasympathetic outflows are generated by distinct, though overlapping, propriobulbar arrays of neuronal microcircuit oscillators constituting networks utilizing mutual excitatory and inhibitory neuronal interactions, residing principally within the metencephalon and myelencephalon, and modulated by synaptic influences from the cerebrum, thalamus, hypothalamus, cerebellum, and mesencephalon and ascending influences deriving from peripheral stimuli relayed by cranial nerve afferent axons. Though the respiratory and cardiovascular regulatory effector mechanisms utilize distinct generators, there exists significant overlap and interconnectivity amongst and between these oscillators and pathways, evidenced reciprocally by breathing modulation of sympathetic oscillations and sympathetic modulation of neural breathing. These coupling mechanisms are well-demonstrated coordinately in sympathetic- and respiratory-related central neuronal and efferent neurogram recordings and quantified by the findings of cross-correlation, spectra, and coherence analyses, combined with empirical interventions including lesioning and pharmacological agonist and antagonist microinjection studies, baroloading, barounloading, and hypoxic and/or hypercapnic peripheral and/or central chemoreceptor stimulation. Sympathetic and parasympathetic central neuronal and efferent neural discharge recordings evidence classic fast rhythms produced by propriobulbar neuronal networks located within the medullary division of the lateral tegmental field, coherent with cardiac sympathetic nerve discharge. These neural efferent nerve discharges coordinately evidence slow synchronous oscillations, constituted by Traube Hering (i.e., high frequency), Mayer wave (i.e., medium or low frequency), and vasogenic autorhythmicity (i.e., very low frequency) wave spectral bands. These oscillations contribute to coupling neural breathing, sympathetic oscillations, and parasympathetic cardiovagal premotoneuronal activity. The mechanisms underlying the origins of and coupling amongst, these waves remains to be unresolved.

Cardiac Autonomic Derangement is Associated with Worse Neurological Outcome in the Very Early Phases of Ischemic Stroke.

Background: Acute ischemic stroke (AIS) is associated with autonomic dysfunction. We evaluated the prognostic value of heart rate variability (HRV) and the role of stroke localization and reperfusion treatment (RT) on autonomic control. Methods: Patients with AIS and sinus rhythm were enrolled in the emergency department. Autonomic parameters were recorded at the onset and after a potential RT. Neurological deficit was assessed using the National Institute of Health Stroke Scale (NIHSS) at the onset and residual disability with modified Rankin Scale (mRS) at 3 months. Two analyses were used to assess HRV. Low frequency (LF) and high frequency (HF) are, respectively, markers of sympathetic and respiratory vagal modulation in spectral analysis. Symbolic analysis provides pattern with no variation (0V%) as an index of sympathetic modulation and pattern with two like variations (2LV%) and pattern with two unlike variations (2UV%) as markers of vagal modulation. Results: We enrolled 41 patients. Twenty-seven underwent RT. A prevalent parasympathetic modulation was found in patients with NIHSS ≥14. The group with mRS 3–6 exhibited a higher 2UV% and lower 0V%. Right-sided strokes were associated with a higher respiratory vagal control. RT had no effects on HRV parameters. Conclusions: In the very early phases of AIS, a decreased 0V% and an increased 2UV% may reflect a loss of sympathetic oscillation, predicting a poorer 3 month-outcome.

Role of ventral medullary catecholaminergic neurons for respiratory modulation of sympathetic outflow in rats

Sympathetic activity displays rhythmic oscillations generated by brainstem inspiratory and expiratory neurons. Amplification of these rhythmic respiratory-related oscillations is observed in rats under enhanced central respiratory drive or during development of neurogenic hypertension. Herein, we evaluated the involvement of ventral medullary sympatho-excitatory catecholaminergic C1 neurons, using inhibitory Drosophila allatostatin receptors, for the enhanced expiratory-related oscillations in sympathetic activity in rats submitted to chronic intermittent hypoxia (CIH) and following activation of both peripheral (hypoxia) and central chemoreceptors (hypercapnia). Pharmacogenetic inhibition of C1 neurons bilaterally resulted in reductions of their firing frequency and amplitude of inspiratory-related sympathetic activity in rats in normocapnia, hypercapnia or after CIH. In contrast, hypercapnia or hypoxia-induced enhanced expiratory-related sympathetic oscillations were unaffected by C1 neuronal inhibition. Inhibition of C1 neurons also resulted in a significant fall in arterial pressure and heart rate that was similar in magnitude between normotensive and CIH hypertensive rats, but basal arterial pressure in CIH rats remained higher compared to controls. C1 neurons play a key role in regulating inspiratory modulation of sympathetic activity and arterial pressure in both normotensive and CIH hypertensive rats, but they are not involved in the enhanced late-expiratory-related sympathetic activity triggered by activation of peripheral or central chemoreceptors.

Contribution of Autonomic Reflexes to the Hyperadrenergic State in Heart Failure.

Heart failure (HF) is a complex syndrome representing the clinical endpoint of many cardiovascular diseases of different etiology. Given its prevalence, incidence and social impact, a better understanding of HF pathophysiology is paramount to implement more effective anti-HF therapies. Based on left ventricle (LV) performance, HF is currently classified as follows: (1) with reduced ejection fraction (HFrEF); (2) with mid-range EF (HFmrEF); and (3) with preserved EF (HFpEF). A central tenet of HFrEF pathophysiology is adrenergic hyperactivity, featuring increased sympathetic nerve discharge and a progressive loss of rhythmical sympathetic oscillations. The role of reflex mechanisms in sustaining adrenergic abnormalities during HFrEF is increasingly well appreciated and delineated. However, the same cannot be said for patients affected by HFpEF or HFmrEF, whom also present with autonomic dysfunction. Neural mechanisms of cardiovascular regulation act as “controller units,” detecting and adjusting for changes in arterial blood pressure, blood volume, and arterial concentrations of oxygen, carbon dioxide and pH, as well as for humoral factors eventually released after myocardial (or other tissue) ischemia. They do so on a beat-to-beat basis. The central dynamic integration of all these afferent signals ensures homeostasis, at rest and during states of physiological or pathophysiological stress. Thus, the net result of information gathered by each controller unit is transmitted by the autonomic branch using two different codes: intensity and rhythm of sympathetic discharges. The main scope of the present article is to (i) review the key neural mechanisms involved in cardiovascular regulation; (ii) discuss how their dysfunction accounts for the hyperadrenergic state present in certain forms of HF; and (iii) summarize how sympathetic efferent traffic reveal central integration among autonomic mechanisms under physiological and pathological conditions, with a special emphasis on pathophysiological characteristics of HF.

Flexible RFID Tag Inductor Printed by Liquid Metal Ink Printer and Its Characterization

In order to fulfill various growing needs of application fields, the development of low-cost directly printable radio-frequency identification (RFID) tag is essential for item level tracking. Currently, there lacks an easily available way to directly write out functional consumer electronicslike typewriting on paper by an office printer. Here, we show a desktop printing of RFID tag inductors on flexible substrates via developing liquid metal ink and related working mechanisms. The directly printing inductor on various flexible substrates with extremely low cost and rapid speed was designed based on the sympathetic oscillations of multiple LC (inductor–capacitor) circuits. In order to better meet the demands of the distinct resonant circuits, a series of conceptual experiments for investigating the relationship between the character of the inductor and its parameters—shape, number of coils, line width, spacing, etc.,—have been designed. The parameters are all working upon the performance of the printed inductors by liquid metal ink printer, and the relationship laws are consistent with those of the conventional inductors. The coils number as the biggest effect factor has a linear relationship with the inductance of the spiral-type inductors. An inductor with excellent properties can be well chosen by adjusting its parameters according to various applications. The present work demonstrated the way for a low cost and easy going method in directly printing RFID tag inductors on flexible substrates.

Role of Calcitonin Gene-Related Peptide in Cooling-Induced Hemodynamic Perturbations in Rats: Investigation by Spectrum Analysis

Calcitonin gene-related peptide (CGRP) and its receptors are widely distributed in the nervous and cardiovascular systems as a potent vasodilator; however, the underlying mechanisms of action of CGRP on cardiovascular regulation, such as cooling-elicited hemodynamic perturbation (CEHP), are still unclear. We used spectral and crossspectral analyses to explore such questions in this study. Conscious rats were pretreated with the CGRP antagonist CGRP_(8-37)-only, or following the removal of sympathetic influences using hexamethonium (HEX) or guanethidine (GUA) and then subjected the treated rats to a stressful cooling trial (CS). Cardiovascular indices were monitored via an implanted telemetric device throughout the experiment. The analyses included measurements of blood pressure (BP), heart rate (HR), cardiovascular variabilities (BPV, HRV), coherence linkage at very-low, low and high frequency regions (VLF: 0.02 to 0.2 Hz, LF: 0.2 to 0.6 Hz, and HF: 0.6 to 3.0 Hz), and dicrotic notch (Dn). Key findings of the hemodynamic indices and spectral changes in efferent sympathetic oscillations (LF) and myogenic oscillations (VLF) in comparison with the control vehicle were demonstrated: (I) under resting condition, CGRP_(8-37)- only increased the BP, HR and powers of VLF_(BPV), LF_(BPV). In contrast, the effects of CGRP_(8-37)-only were generally diminished or further reduced when the rats were pretreated with HEX or GUA. (II) Under CS condition, CGRP_(8-37)-only increased the HR but attenuated the power of LF_(BPV), converted the negative correlation (NC) into positive correlation (PC) for VLF_(HRV) with VLF_(BPV) (VLF pair) and LF_(HRV) with LF_(BPV) (LF pair). On the other hand, when pretreated with sympathetic removals, both HEX+CGRP_(8-37) and GUA+CGRP_(8-37) generally abolished the control coolinginduced pressor and tachycardia, attenuated or further reduced the effects of CGRP_(8-37)-only on VLF_(BPV), VLF_(HRV) and LF_(BPV). In addition, HEX+CGRP_(8-37) generally persisted the CGRP_(8-37)-only effect of PC for VLF and LF pairs, but GUA reversed the PC of VLF pair back to a NC tendency. Furthermore, cross-spectral analyses indicated that throughout the experiment, CGRP8-37-only enhanced the coherence linkage between BPV and HRV at the LF region but weakened that at the HF region. HEX+CGRP_(8-37) abolished the CGRP_(8-37)-only effect on the LF region but GUA+CGRP_(8-37) persisted the CGRP_(8-37)-only effects. Taken together, our results indicate that CGRP is dependent on the status of intrinsic sympathetic tonus to exert its function on cardiovascular regulation.

Stretchable RFID for Wireless Strain Sensing With Silver Nano Ink

Flexible and stretchable inductor-capacitor (LC) resonator-based chipless radio frequency identification (RFID) tags have been fabricated by the direct stamping with silver nano ink. The tags are optimized based on the sympathetic oscillation of LC circuit at specifically designed resonant frequencies ranged from 1.12 to 1.7 GHz by adjusting dimensions of the inductor and capacitor in a tag. Pressure applied to the layer of silver nano ink during the stamping procedure helps densification of silver nanoparticles inside trenches of the stamp before heat-annealing of them. Transfer stamping process is simulated to demonstrate stress distribution across the layer of silver nanoparticles. Compaction of silver nanoparticles, in turn, positively affects mechanical strength of the final silver electrode and enables RFID strain sensors on polydimethylsiloxane to be stretchable up to 7%. By the stretchable RFID strain sensors, wireless strain sensing is demonstrated with a gauge factor of 0.51. Multiple encoded identifications with combination of double tags and stretching behavior of fabricated tags are also demonstrated. This stretchable RFID sensor is promising for biomedical applications such as real-time monitoring of motion detection.

The nucleus of the solitary tract and the coordination of respiratory and sympathetic activities.

It is well known that breathing introduces rhythmical oscillations in the heart rate and arterial pressure levels. Sympathetic oscillations coupled to the respiratory activity have been suggested as an important homeostatic mechanism optimizing tissue perfusion and blood gas uptake/delivery. This respiratory-sympathetic coupling is strengthened in conditions of blood gas challenges (hypoxia and hypercapnia) as a result of the synchronized activation of brainstem respiratory and sympathetic neurons, culminating with the emergence of entrained cardiovascular and respiratory reflex responses. Studies have proposed that the ventrolateral region of the medulla oblongata is a major site of synaptic interaction between respiratory and sympathetic neurons. However, other brainstem regions also play a relevant role in the patterning of respiratory and sympathetic motor outputs. Recent findings suggest that the neurons of the nucleus of the solitary tract (NTS), in the dorsal medulla, are essential for the processing and coordination of respiratory and sympathetic responses to hypoxia. The NTS is the first synaptic station of the cardiorespiratory afferent inputs, including peripheral chemoreceptors, baroreceptors and pulmonary stretch receptors. The synaptic profile of the NTS neurons receiving the excitatory drive from afferent inputs is complex and involves distinct neurotransmitters, including glutamate, ATP and acetylcholine. In the present review we discuss the role of the NTS circuitry in coordinating sympathetic and respiratory reflex responses. We also analyze the neuroplasticity of NTS neurons and their contribution for the development of cardiorespiratory dysfunctions, as observed in neurogenic hypertension, obstructive sleep apnea and metabolic disorders.

Respiratory, metabolic and cardiac functions are altered by disinhibition of subregions of the medial prefrontal cortex

The prefrontal cortex (PFC) is referred to as the visceral motor cortex; however, little is known about whether this region influences respiratory or metabolic outflows. The aim of this study was to describe simultaneous changes in respiratory, metabolic and cardiovascular functions evoked by disinhibition of the medial PFC (mPFC) and adjacent lateral septal nucleus (LSN). In urethane-anaesthetized rats, bicuculline methiodide was microinjected (2 mm; GABA-A receptor antagonist) into 90 sites in the mPFC at 0.72-4.00 mm from bregma. Phrenic nerve amplitude and frequency, arterial pressure, heart rate, splanchnic and lumbar sympathetic nerve activities (SNA), expired CO2, and core and brown adipose tissue temperatures were measured. Novel findings included disturbances to respiratory rhythm evoked from all subregions of the mPFC. Injections into the cingulate cortex evoked reductions in central respiratory function exclusively, whereas in ventral sites, particularly the infralimbic region, increases in respiratory drive and frequency, and metabolic and cardiac outflows were evoked. Disinhibition of sites in surrounding regions revealed that the LSN could evoke cardiovascular changes accompanied by distinct oscillations in SNA, as well as increases in respiratory amplitude. We show that activation of neurons within the mPFC and LSN influence respiratory, metabolic and cardiac outflows in a site-dependent manner. This study has implications with respect to the altered PFC neuronal activity seen in stress-related and mental health disorders, and suggests how basic physiological systems may be affected.

Time-frequency methods and voluntary ramped-frequency breathing: a powerful combination for exploration of human neurophysiological mechanisms

We experimentally altered the timing of respiratory motoneuron activity as a means to modulate and better understand otherwise hidden human central neural and hemodynamic oscillatory mechanisms. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations, and muscle sympathetic nerve activity in 13 healthy supine young men who gradually increased or decreased their breathing frequencies between 0.05 and 0.25 Hz over 9-min periods. We analyzed results with traditional time- and frequency-domain methods, and also with time-frequency methods (wavelet transform, wavelet phase coherence, and directional coupling). We determined statistical significance and identified frequency boundaries by comparing measurements with randomly generated surrogates. Our results support several major conclusions. First, respiration causally modulates both sympathetic (weakly) and vagal motoneuron (strongly) oscillations over a wide frequency range-one that extends well below the frequency of actual breaths. Second, breathing frequency broadly modulates vagal baroreflex gain, with peak gains registered in the low frequency range. Third, breathing frequency does not influence median levels of sympathetic or vagal activity over time. Fourth, phase relations between arterial pressure and sympathetic and vagal motoneurons are unaffected by breathing, and are therefore likely secondary to intrinsic responsiveness of these motoneurons to other synaptic inputs. Finally, breathing frequency does not affect phase coherence between diastolic pressure and muscle sympathetic oscillations, but it augments phase coherence between systolic pressure and R-R interval oscillations over a limited portion of the usual breathing frequency range. These results refine understanding of autonomic oscillatory processes and those physiological mechanisms known as the human respiratory gate.

Coherent phonon manipulation in coupled mechanical resonators

It is now shown that phonons can be coherently transferred between two nanomechanical resonators. The technique of controlling the coupling between nanoscale oscillators using a piezoelectric transducer is useful for manipulating classical oscillations, but if extended to the quantum regime it could also enable entanglement of macroscopic mechanical objects. Coupled nanomechanical resonators have recently attracted great attention for both practical applications and fundamental studies owing to their sensitive sympathetic oscillation dynamics1,2,3,4,5,6,7,8,9,10. A challenge to the further development of this architecture is the coherent manipulation of the coupled oscillations. Here, we demonstrate strong dynamic coupling between two GaAs-based mechanical resonators by periodically modulating (pumping) the stress using a piezoelectric transducer. This strong coupling enables coherent transfer of phonon populations between the resonators, namely phonon Rabi oscillations11,12,13. The nature of the dynamic coupling can also be tuned from a linear first-order interaction to a nonlinear higher-order process in which more than one pump phonon mediates the coherent oscillations (that is, multi-pump phonon mixing). This coherent manipulation is not only useful for controlling classical oscillations14 but can also be extended to the quantum regime11,12,13, opening up the prospect of entangling two distinct macroscopic mechanical objects15,16.

Human sympathetic outflows to skin and muscle target organs fluctuate concordantly over a wide range of time‐varying frequencies

Frequency-domain analyses of simultaneously recorded skin and muscle sympathetic nerve activities may yield unique information on otherwise obscure central processes governing human neural outflows. We used wavelet transform and wavelet phase coherence methods to analyse integrated skin and muscle sympathetic nerve activities and haemodynamic fluctuations, recorded from nine healthy supine young men. We tested two null hypotheses: (1) that human skin and muscle sympathetic nerve activities oscillate congruently; and (2) that whole-body heating affects these neural outflows and their haemodynamic consequences in similar ways. Measurements included peroneal nerve skin and tibial nerve muscle sympathetic activities; the electrocardiogram; finger photoplethysmographic arterial pressure; respiration (controlled at 0.25 Hz, and registered with a nasal thermistor); and skin temperature, sweating, and laser-Doppler skin blood flow. We made recordings at ∼27°C, for ∼20 min, and then during room temperature increases to ∼38°C, over 35 min. We analysed data with a wavelet transform, using the Morlet mother wavelet and wavelet phase coherence, to determine the frequencies and coherences of oscillations over time. At 27°C, skin and muscle nerve activities oscillated coherently, at ever-changing frequencies between 0.01 and the cardiac frequency (∼1 Hz). Heating significantly augmented oscillations of skin sympathetic nerve activity and skin blood flow, arterial pressure, and R-R intervals, over a wide range of low frequencies, and modestly reduced coordination between skin and muscle sympathetic oscillations. These results suggest that human skin and muscle sympathetic motoneurones are similarly entrained by external influences, including those of arterial baroreceptors, respiration, and other less well-defined brainstem oscillators. Our study provides strong support for the existence of multiple, time-varying central sympathetic neural oscillators in human subjects.

Design of fully printable and configurable chipless RFID tag on flexible substrate

AbstractThis article presents the design and implementation of a chipless radio frequency identification (RFID) tag on flexible substrate.The tag is designed based on the sympathetic oscillations of multiple LC (inductor–capacitor) circuits that possess distinct resonant frequencies. Information is encoded by controlling placement of these resonant frequencies. To trade off the readability and size of the tag, the optimizations including capacitor placements and different LC combinations are studied. The tag is then realized onto flexible polyimide substrate using toner‐transferring process. The detection system is also constructed and used to measure the proposed tag. The measurement results show that the tag can provide an excellent readability more than 20 cm reading range. In addition, this tag is fully printable and configurable, hence making it more feasible and considerably cheaper to be used. This tag can provide a meaningful approach toward the realization of ultralow‐cost RFID tags attached onto low‐value items. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:226–230, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26499

Sympathetic current oscillations at an enzyme electrode induced by potential oscillations at a Pt surface

A dual-electrode set-up is introduced in order to demonstrate that electrochemical oscillations at one electrode can induce sympathetic oscillations at the other electrode. A pure Pt surface is used as a primary electrode at which the potential oscillations of the [ Fe ( CN ) 6 ] 3 - system with convective feedback occur and stimulate current oscillations at a Pt or glucose oxidase enzyme (GOD) + tetraethyl silicate (TEOS) coated electrode placed in the vicinity. The current density of the primary electrode and glucose concentration can be used to influence the frequency and amplitude of oscillations at the GOD + TEOS electrode.