Frequency Gradient Research Articles

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Layer II stellate cells at different locations along the dorsal to ventral axis of medial entorhinal cortex show differences in the frequency of intrinsic membrane potential oscillations and resonance (Giocomo et al., 2007). The frequency differences scale with differences in the size and spacing of grid-cell firing fields recorded in layer II of the medial entorhinal cortex in behaving animals. To determine the mechanism for this difference in intrinsic frequency, we analyzed oscillatory properties in adult control mice and adult mice with a global deletion of the HCN1 channel. Data from whole-cell patch recordings show that the oscillation frequency gradient along the dorsal–ventral axis previously shown in juvenile rats also appears in control adult mice, indicating that the dorsal–ventral gradient generalizes across age and species. Knock-out of the HCN1 channel flattens the dorsal–ventral gradient of the membrane potential oscillation frequency, the resonant frequency, the time constant of the “sag” potential and the amplitude of the sag potential. This supports a role of the HCN1 subunit in the mechanism of the frequency gradient in these neurons. These findings have important implications for models of grid cells and generate predictions for future in vivo work on entorhinal grid cells.

EFFECT OF FRETS TO SOUND FREQUENCY OF SUNDATANG

Sundatang is a traditional musical instrument in Sabah, Malaysia, which is needs to be upgraded. The purpose of this study was to formulate equations that explaining the effect of frets to its sound frequency. Sound of sundatang was recorded using a microphone which was connected to ADC Harmonie system. In this study, it was found that the fundamental frequency of sound of the 1st string shifted to higher frequency when fretted at higher fret number. There are two equations formulated in this study which can be used to calculate the fundamental frequency of sound at each fret of sundatang, named Fundamental Frequency (FF) equation and Gradient Harmonic Frequency (GHF) equation. Where, the maximum average difference obtained between recorded and calculated frequency is 4.53 Hz. In addition, also formulated an equation that can be used to explain the correlation of the fundamental frequency and the length of the fretted of 1st string which is named as Correlation of Fundamental Frequency with Length of Fretted String (CFFLFS) equation. The formulated equations in this study can be used to develop a standard musical notation of sundatang.

A quest for species‐level indicator values for disturbance

AbstractQuestionIs it possible to construct indicator values that would place individual species on gradients of disturbance frequency and severity? We suggest that such indicator values could be defined on the basis of the disturbance regimes under which individual species occur, to be independent of their traits. They should also separate disturbance frequency from disturbance severity.LocationCzech Republic.MethodsWe used a stratified set of 30 115 vegetation‐plot records sampled over the whole country and classified into 39 phytosociological vegetation classes. Each class was assigned values of disturbance frequency and severity by expert judgement. A Disturbance Frequency Index for each species was calculated as the mean of the common logarithm of the disturbance frequency of all vegetation classes weighted by occurrence frequencies of this species in those classes. A Disturbance Severity Index was defined as mean disturbance severity of all vegetation classes weighted by occurrence frequencies of this species in those classes. For forest vegetation, indices were computed separately for the whole community and for the herb layer, which experiences different types of disturbance. Further, we constructed a disturbance index from vegetation structural parameters, viz. summed covers and community‐weighted mean of height at maturity of species recorded in each plot for each vegetation class. We assessed all indices by comparing their values with data on functional traits of the species.ResultsWe calculated values of the indices for 1248 species. The Disturbance Frequency Index and Disturbance Severity Index were correlated, but still described different responses of individual species to disturbance. The index based on vegetation structure was correlated mainly with the Disturbance Frequency Index. All indices showed strong relationships to plant traits: species with high values of all disturbance indices tended to have small seeds, to be annual and non‐clonal or able to spread clonally over large distances.ConclusionsConstructing species disturbance indices based on vegetation characteristics, not plant traits, is feasible and provides meaningful scores. A similar approach can be used in any region where sufficient vegetation data are available. Disturbance indices can be used to address a number of questions in plant evolution and community or landscape ecology.

Identification of Dominant Excitation Patterns and Sources of Atrial Fibrillation by Causality Analysis

Burden of atrial fibrillation (AF) can be reduced by ablation of sources of electrical impulses driving AF but driver identification is still challenging. This study presents a new methodology based on causality analysis that allows identifying the hierarchically dominant areas driving AF. Identification of dominant propagation patterns was achieved by computing causal relations between intracardiac multi-electrode catheter recordings of four paroxysmal AF patients during sinus rhythm, pacing and AF. In addition, realistic mathematical models of the atria during AF were used to validate the methodology both in the presence and absence of dominant frequency (DF) gradients. During electrical pacing, sources of propagation patterns detected by causality analysis were consistent with the location of the stimulating catheter. During AF, propagation patterns presented temporal variability, but a dominant direction accounted for significantly more propagations than other directions (49±15% vs. 14±13% or less, p<0.01). Both in patients with a DF gradient and in mathematical models, causal maps allowed the identification of sites responsible for maintenance of AF. Causal maps allowed the identification of atrial dominant sites. In particular, causality analysis resulted in stable dominant cause-effect propagation directions during AF and could serve as a guide for performing ablation procedures in AF patients.

Spatial Noise in Coupling Strength and Natural Frequency within a Pacemaker Network; Consequences for Development of Intestinal Motor Patterns According to a Weakly Coupled Phase Oscillator Model.

Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency.

Natural Vocalizations in the Mammalian Inferior Colliculus are Broadly Encoded by a Small Number of Independent Multi-Units.

How complex natural sounds are represented by the main converging center of the auditory midbrain, the central inferior colliculus, is an open question. We applied neural discrimination to determine the variation of detailed encoding of individual vocalizations across the best frequency gradient of the central inferior colliculus. The analysis was based on collective responses from several neurons. These multi-unit spike trains were recorded from guinea pigs exposed to a spectrotemporally rich set of eleven species-specific vocalizations. Spike trains of disparate units from the same recording were combined in order to investigate whether groups of multi-unit clusters represent the whole set of vocalizations more reliably than only one unit, and whether temporal response correlations between them facilitate an unambiguous neural representation of the vocalizations. We found a spatial distribution of the capability to accurately encode groups of vocalizations across the best frequency gradient. Different vocalizations are optimally discriminated at different locations of the best frequency gradient. Furthermore, groups of a few multi-unit clusters yield improved discrimination over only one multi-unit cluster between all tested vocalizations. However, temporal response correlations between units do not yield better discrimination. Our study is based on a large set of units of simultaneously recorded responses from several guinea pigs and electrode insertion positions. Our findings suggest a broadly distributed code for behaviorally relevant vocalizations in the mammalian inferior colliculus. Responses from a few non-interacting units are sufficient to faithfully represent the whole set of studied vocalizations with diverse spectrotemporal properties.

Discrete Fourier Transform Method for Discrimination of Digital Scintillation Pulses in Mixed Neutron-Gamma Fields

A Discrete Fourier Transform Method (DFTM) for discrimination between the signal of neutrons and gamma rays in organic scintillation detectors is presented. The method is based on the transformation of signals into the frequency domain using the sine and cosine Fourier transforms in combination with the discrete Fourier transform. The method is largely benefited from considerable differences that usually is available between the zero-frequency components of sine and cosine and the norm of the amplitude of the DFT for neutrons and gamma-ray signals. Moreover, working in frequency domain naturally results in considerable suppression of the unwanted effects of various noise sources that is expected to be effective in time domain methods. The proposed method could also be assumed as a generalized nonlinear weighting method that could result in a new class of pulse shape discrimination methods, beyond definition of the DFT. A comparison to the traditional Charge Integration Method (CIM), as well as the Frequency Gradient Analysis Method (FGAM) and the Wavelet Packet Transform Method (WPTM) has been presented to demonstrate the applicability and efficiency of the method for real-world applications. The method, in general, shows better discrimination Figure of Merits (FoMs) at both the low-light outputs and in average over the studied energy domain. A noise analysis has been performed for all of the abovementioned methods. It reveals that the frequency domain methods (FGAM and DFTM) are less sensitive to the noise effects.

Differences in disturbance type and nutrient availability favour different functional traits across three co-occurring montane wetland systems in eastern Australia

Three co-occurring temperate montane non-riparian freshwater wetland communities of the New England Batholith of eastern Australia were chosen to test differences in resource allocation to select functional traits. Each of the wetlands was tested against inferred gradients of nutrient availability, fire and disturbance frequency. Collated functional trait data on 563 native vascular plant taxa known to occur in bogs, fens and lagoons were used against a centrally weighted means redundancy analysis. Traits included life form, plant height, leaf area, fruit size, seed size, mono- or polycarpy, storage organs, fruit type, vegetative spread and geographic range size. Where disturbances were moderate to low in frequency and habitats persistent, tolerance and in-situ permanence traits were favoured. With high nutrient availability and a low disturbance regime polycarpic species with large leaves that allow for larger fruit development were more common. Under low nutrient availability and a moderate disturbance regime, persistence was shifted to a longer lived polycarpic life history that includes woody taxa with increased seed size and a greater diversity of fruit types. In frequently inundated habitats, with shifting windows of available habitats, avoidance was the best strategy. Here persistence shifts to long-lived soil stored diaspores and a monocarpic life history with rapid vegetative growth to capture above ground spatial resource within temporary habitats.

Haustral boundary contractions in the proximal 3-taeniated rabbit colon.

The rabbit proximal colon is similar in structure to the human colon. Our objective was to study interactions of different rhythmic motor patterns focusing on haustral boundary contractions, which create the haustra, using spatiotemporal mapping of video recordings. Haustral boundary contractions were seen as highly rhythmic circumferential ring contractions that propagated slowly across the proximal colon, preferentially but not exclusively in the anal direction, at ∼0.5 cycles per minute; they were abolished by nerve conduction blockers. When multiple haustral boundary contractions propagated in the opposite direction, they annihilated each other upon encounter. Ripples, myogenic propagating ring contractions at ∼9 cycles per min, induced folding and unfolding of haustral muscle folds, creating an anarchic appearance of contractile activity, with different patterns in the three intertaenial regions. Two features of ripple activity were prominent: frequent changes in propagation direction and the occurrence of dislocations showing a frequency gradient with the highest intrinsic frequency in the distal colon. The haustral boundary contractions showed an on/off/on/off pattern at the ripple frequency, and the contraction amplitude at any point of the colon showed waxing and waning. The haustral boundary contractions are therefore shaped by interaction of two pacemaker activities hypothesized to occur through phase-amplitude coupling of pacemaker activities from interstitial cells of Cajal of the myenteric plexus and of the submuscular plexus. Video evidence shows the unique role haustral folds play in shaping contractile activity within the haustra. Muscarinic agents not only enhance the force of contraction, they can eliminate one and at the same time induce another neurally dependent motor pattern.

Soil chemical and physical properties after skidding by rubber-tired skidder in Hyrcanian forest, Iran

This study evaluates the effects of ground-skidding operations on the physical and chemical properties of soil at different levels of slope gradient and traffic frequency. Three levels of traffic (four, eight and 16 passes of a rubber-tired skidder Timberjack 450 C), and two levels of slope gradients (gentle <20%, and steep ≥20%) were applied in three replicates consequently, 18 plots with 10m long by 4m wide were utilized in the study. In each sampling plot, three lines were set up perpendicular to the skidding direction. At three different points on each line (left track, between track and right track) one sample was taken from forest floor and the 0–10cm soil layer. Soil bulk density, forest floor biomass, organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K) and soil acidity (pH) were affected by traffic frequency and slope gradient. The soil class of our study area in soil classification according to WRB was Combisols. Soil texture was analyzed using the Bouyoucos hydrometer method and was determined to be clay loam along the trails. Soil bulk density was 60% higher in samples taken from skid trails compared with samples taken from an undisturbed area. The average forest floor biomass ranged from 2185kgha−1 to 243kgha−1 on the skid trails, while the respective value was 3335kgha−1 for the undisturbed area. Skidding caused a decrease in the amount of soil OC (by 38%) and the concentrations of N (57%), P (25%), K (31%) and hydrogen ions (33%) compared with undisturbed areas. Increased soil disturbance occurred more markedly with fewer passes on the steeper trail. The dramatic increase in soil disturbance on the skid trail with a slope >20% is presumably associated with the difficulties of skidding on steep terrain. To minimize soil disturbance, skidding should be confined to areas with more gentle slopes and alternative harvesting methods should be used where slope gradients exceed 20%. We hypothesized that skidding can jeopardize the sustainability of forest ecosystems by creating unfavorable changes in soil characteristics and nutrient status.

Abstract 10199: Right Atrial Fibrillation in Humans - Evidence for A Right Atrial Driver Activated by Right Atrial Ectopies

Background: A left-to-right dominant frequency (DF) gradient exists in acute atrial fibrillation (AF) in animals and in paroxysmal AF (PAF) in humans. PAF initiated by right atrial ectopy (PAF-RAE) is rare. Adenosine triphosphate (ATP) can be effective to unmask such a rare non-pulmonary vein (PV) ectopy and accelerate the frequency of a reentrant source of AF (driver). Objective: This study aimed to investigate characteristics of patients with PAF-RAE using pharmacological maneuvers and spectral analysis. Methods: Enrolled were 111 consecutive patients referred for catheter ablation of lone PAF. Infusions of isoproterenol and ATP were used to induce AF. Patients with PAF initiated only by PV ectopies and with PAF-RAE were classified into the PV-ectopy group (N=32) and RA-ectopy group (N=6), respectively. ATP was also injected during ongoing AF to unmask the AF driver. High RA, coronary sinus (CS), and PV-left atrial junction (PV-LAJ) electrograms underwent spectral analyses. Results: RA-ectopy group patients were younger (49±13 vs. 63±7 years, p&lt;0.001), more commonly had a family history of AF (67% vs. 9%, p&lt;0.001), and had a higher RA appendage/RA volume ratio (0.22±0.022 vs. 0.15±0.055, p=0.002) than PV-ectopygroup patients. The most common origin of RA ectopy was the base of the RA appendage (67%). There was a baseline right-to-left DF gradient in the RA-ectopy group (PV-LAJ: 6.0±0.4, CS: 5.7±0.7, RA: 7.4±0.8 Hz, p&lt;0.05), in contrast to a left-to-right DF gradient in the PV-ectopy group (PV-LAJ: 5.9±0.8, CS: 5.3±0.7, RA: 5.2±0.8 Hz, p&lt;0.01). ATP injection mainly increased the DF of the high RA, augmenting a right-to-left DF gradient in the RA ectopy group (PV-LAJ: 8.0±2.0, CS: 7.8±1.0, RA: 10.7±0.7 Hz, p&lt;0.05), whereas it augmented a left-to-right DF gradient in the PV-ectopy group (PV-LAJ: 7.9±1.0, CS: 6.4±0.5, RA: 6.6±1.2 Hz, p&lt;0.05). Conclusions: PAF-RAE may be maintained by a reentrant driver localized in the RA (so-called right atrial fibrillation).

All-optical evaluation of spin-orbit interaction based on diffusive spin motion in a two-dimensional electron gas

A method is presented that enables the measurement of spin-orbit coefficients in a diffusive two-dimensional electron gas without the need for processing the sample structure, applying electrical currents or resolving the spatial pattern of the spin mode. It is based on the dependence of the average electron velocity on the spatial distance between local excitation and detection of spin polarization, resulting in a variation of spin precession frequency that in an external magnetic field is linear in the spatial separation. By scanning the relative positions of the exciting and probing spots in a time-resolved Kerr rotation microscope, frequency gradients along the [100] and [010] crystal axes of GaAs/AlGaAs QWs are measured to obtain the Rashba and Dresselhaus spin-orbit coefficients, α and β. This simple method can be applied in a variety of materials with electron diffusion for evaluating spin-orbit coefficients.

Ventricular Tachycardia and Early Fibrillation in Patients With Brugada Syndrome and Ischemic Cardiomyopathy Show Predictable Frequency-Phase Properties on the Precordial ECG Consistent With the Respective Arrhythmogenic Substrate.

Ventricular fibrillation (VF) has been proposed to be maintained by localized high-frequency sources. We tested whether spectral-phase analysis of the precordial ECG enabled identification of periodic activation patterns generated by such sources. Precordial ECGs were recorded from 15 ischemic cardiomyopathy and 15 Brugada syndrome (type 1 ECG) patients during induced VF and analyzed in the frequency-phase domain. Despite temporal variability, induced VF episodes lasting 19.6±7.9 s displayed distinctly high power at a common frequency (shared frequency, 5.7±1.1 Hz) in all leads about half of the time. In patients with Brugada syndrome, phase analysis of shared frequency showed a V1-V6 sequence as would be expected from patients displaying a type 1 ECG pattern (P<0.001). Hilbert-based phases confirmed that the most stable sequence over the whole VF duration was V1-V6. Analysis of shared frequency in ischemic cardiomyopathy patients with anteroseptal (n=4), apical (n=3), and inferolateral (n=4) myocardial infarction displayed a sequence starting at V1-V2, V3-V4, and V5-V6, respectively, consistent with an activation origin at the scar location (P=0.005). Sequences correlated with the Hilbert-based phase analysis (P<0.001). Posterior infarction (n=4) displayed no specific sequence. On paired comparison, phase sequences during monomorphic ventricular tachycardia correlated moderately with VF (P<0.001). Moreover, there was a dominant frequency gradient from precordial leads facing the scar region to the contralateral leads (5.8±0.8 versus 5.4±1.1 Hz; P=0.004). Noninvasive analysis of ventricular tachycardia and early VF in patients with Brugada syndrome and ischemic cardiomyopathy shows a predictable sequence in the frequency-phase domain, consistent with anatomic location of the arrhythmogenic substrate.

Right-to-left frequency gradient during atrial fibrillation initiated by right atrial ectopies and its augmentation by adenosine triphosphate: Implications of right atrial fibrillation

A left-to-right dominant frequency (DF) gradient commonly exists in paroxysmal atrial fibrillation (AF). AF initiated by right atrial (RA) ectopy (AF-RAE) is rare. This study aimed to investigate characteristics of AF-RAE using pharmacological maneuvers and spectral analysis. Seventy-nine consecutive patients referred for catheter ablation of paroxysmal AF were enrolled. Infusions of isoproterenol and adenosine triphosphate (ATP) were used to induce AF. Patients with AF-RAE and patients with AF initiated only by pulmonary vein (PV) ectopies were classified into the RA-ectopy group (n = 7[9%]) and PV-ectopy group (n = 32[41%]), respectively. ATP was also injected during ongoing AF to unmask the driver of AF. High RA, coronary sinus, and PV-left atrial junction electrograms and electrocardiogram lead V1 underwent spectral analyses. Patients in the RA-ectopy group were younger (51 ± 13 years vs 63 ± 7 years; P = .01) and more commonly had a family history of AF (71% vs 9%; P < .001) than patients in the PV-ectopy group. There was a baseline right-to-left DF gradient in the RA-ectopy group (PV-left atrial junction: 6.0 ± 0.4 Hz; coronary sinus: 5.7 ± 0.6 Hz; RA: 7.3 ± 0.8 Hz; P < .05) in contrast to a left-to-right DF gradient in the PV-ectopy group (5.9 ± 0.8, 5.3 ± 0.7, 5.2 ± 0.8 Hz; P < .01). ATP injection predominantly increased the DF of the high RA in the RA-ectopy group and augmented a right-to-left DF gradient (7.9 ± 1.8, 7.6 ± 1.0, 10.7 ± 0.7 Hz; P < .001), whereas it augmented a left-to-right DF gradient in the PV-ectopy group (7.9 ± 1.0, 6.4 ± 0.5, 6.6 ± 1.2 Hz; P < .05). A rare type of paroxysmal AF initiated by RA ectopy may be maintained by a reentrant driver localized in the RA (so-called RA fibrillation).

Fire regime, soil fertility and growth form interact to shape fire and growth traits in two co-occurring Banksia species

Inter- and intra-specific comparisons were made between several co-occurring populations of two Banksia species growing in Eastern Australian dry sclerophyll open woodland that experiences a grass-fueled surface-fire regime. The two species differ in life-history from a short basal resprouter (B. Neoanglica) to a tall fire-survivor (B. integrifolia). Growth (LMA = leaf mass per unit mass area), persistence (bark thickness) and recruitment (serotiny) traits were determined across independent gradients in soil fertility and fire frequency. Trait correlations for the two species showed distinct patterns, from each other and across environments, with the resprouter having higher LMA and infructescence retention but lower bark thickness. However, there were no consistent intra-specific patterns with variation in fire and soil nutrients. LMA only varied in B. integrifolia with soil fertility, and fire frequency had no effect on either species. Relative bark thickness varied with plant size but not among sites. There was a trend of increasing pyriscence with fire in B. neoanglica and with lower nutrients soils but not in B. integrifolia. Clearly the two species respond differently to variability in nutrients and fire. Nevertheless, growth form appears to be the strongest determinant of both growth (LMA) and fire traits (thicker bark; pyriscence) in these co-existing Banksia species.

Impacts of stratospheric ozone depletion and recovery on wave propagation in the boreal winter stratosphere

AbstractThis paper uses a state‐of‐the‐art general circulation model to study the impacts of the stratospheric ozone depletion from 1980 to 2000 and the expected partial ozone recovery from 2000 to 2020 on the propagation of planetary waves in December, January, and February. In the Southern Hemisphere (SH), the stratospheric ozone depletion leads to a cooler and stronger Antarctic stratosphere, while the stratospheric ozone recovery has the opposite effects. In the Northern Hemisphere (NH), the impacts of the stratospheric ozone depletion on polar stratospheric temperature are not opposite to that of the stratospheric ozone recovery; i.e., the stratospheric ozone depletion causes a weak cooling and the stratospheric ozone recovery causes a statistically significant cooling. The stratospheric ozone depletion leads to a weakening of the Arctic polar vortex, while the stratospheric ozone recovery leads to a strengthening of the Arctic polar vortex. The cooling of the Arctic polar vortex is found to be dynamically induced via modulating the planetary wave activity by stratospheric ozone increases. Particularly interesting is that stratospheric ozone changes have opposite effects on the stationary and transient wave fluxes in the NH stratosphere. The analysis of the wave refractive index and Eliassen‐Palm flux in the NH indicates (1) that the wave refraction in the stratosphere cannot fully explain wave flux changes in the Arctic stratosphere and (2) that stratospheric ozone changes can cause changes in wave propagation in the northern midlatitude troposphere which in turn affect wave fluxes in the NH stratosphere. In the SH, the radiative cooling (warming) caused by stratospheric ozone depletion (recovery) produces a larger (smaller) meridional temperature gradient in the midlatitude upper troposphere, accompanied by larger (smaller) zonal wind vertical shear and larger (smaller) vertical gradients of buoyancy frequency. Hence, there are more (fewer) transient waves propagating into the stratosphere. The dynamical warming (cooling) caused by stratospheric ozone decreases (increases) partly offsets their radiative cooling (warming).

Functional Microarchitecture of the Mouse Dorsal Inferior Colliculus Revealed through In Vivo Two-Photon Calcium Imaging.

Due to its genetic tractability, the mouse is fast becoming the most popular animal model for sensory neuroscience. Nevertheless, many aspects of its neural architecture are still poorly understood. Here, we image the dorsal auditory midbrain and its inputs from the cortex, revealing a hitherto hidden level of organization and paving the way for the direct observation of corticocollicular interactions. We show that a precise functional organization exists in the mouse auditory midbrain, which has been missed by previous, more macroscopic approaches. The fine-scale distribution of sound-frequency tuning suggests that the mouse midbrain is more similar to that of other mammals than previously thought and contrasts with the more heterogeneous organization reported in imaging studies of auditory cortex.

Desert Dust Outbreaks in Southern Europe: Contribution to Daily PM₁₀ Concentrations and Short-Term Associations with Mortality and Hospital Admissions.

Background:Evidence on the association between short-term exposure to desert dust and health outcomes is controversial.Objectives:We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources.Methods:We identified desert dust advection days in multiple Mediterranean areas for 2001–2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis.Results:On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring–summer, with increasing gradient of both frequency and intensity north–south and west–east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0–1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions.Conclusions:PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections.Citation:Stafoggia M, Zauli-Sajani S, Pey J, Samoli E, Alessandrini E, Basagaña X, Cernigliaro A, Chiusolo M, Demaria M, Díaz J, Faustini A, Katsouyanni K, Kelessis AG, Linares C, Marchesi S, Medina S, Pandolfi P, Pérez N, Querol X, Randi G, Ranzi A, Tobias A, Forastiere F, MED-PARTICLES Study Group. 2016. Desert dust outbreaks in Southern Europe: contribution to daily PM10 concentrations and short-term associations with mortality and hospital admissions. Environ Health Perspect 124:413–419; http://dx.doi.org/10.1289/ehp.1409164

Ability of magnetocardiography to detect regional dominant frequencies of atrial fibrillation

BackgroundLead V1 on electrocardiography (ECG) can detect the dominant frequency (DF) of atrial fibrillation (AF) in the right atrium (RA). Paroxysmal AF is characterized by a frequency gradient from the left atrium (LA) to the right atrium (RA). We examined the ability of magnetocardiography (MCG) to detect regional DFs in both the atria. MethodsStudy subjects comprised 18 consecutive patients referred for catheter ablation of persistent AF. An MCG system with 64 magnetic sensors was used to perform MCG in the frontal, lateral, and back planes prior to the ablation procedure in each patient. DFMCG and organization index (OIMCG) were calculated using fast Fourier transformation. Intracardiac electrograms (ICEs) in both the atria and the coronary sinus (CS) were mapped at 17 sites. Regional DFsICE were also determined. ResultsMean LA DFICE was higher than mean RA DFICE (6.40±0.66 versus 6.16±0.80Hz, P=0.03). DFMCG in the channel having the highest OIMCG was 6.61±0.88Hz in the frontal plane, 6.52±0.64Hz in the lateral plane, and 6.42±0.62Hz in the back plane (P=0.3). In each plane, DFMCG correlated with DFICE at the RA appendage (R=0.95, P<0.0001), the LA appendage (R=0.91, P<0.0001), and the CS (R=0.93, P<0.0001). DFECG in V5 modestly correlated with DFICE at the LA appendage (R=0.82, P<0.0001). ConclusionsMCG could more precisely detect the DFs in the LA and the CS than ECG. However, the usefulness of pre-procedural detection of the AF frequency gradient for ablation therapy needs to be evaluated in future prospective studies.

Mechanisms of Long-Duration Ventricular Fibrillation in Human Hearts and Experimental Validation in Canine Purkinje Fibers

ObjectivesThis study sought to determine the characteristics of human LDVF, particularly as it contrasts with short-duration VF (SDVF), and evaluate the role of Purkinje fibers in its maintenance. BackgroundThe electrophysiological mechanisms of long-duration ventricular fibrillation (LDVF) have not been studied in the human heart. MethodsVF was induced in 12 human Langendorff hearts, and the hearts were examined from initiation to LDVF (10 min). Endocardial, epicardial, and transmural plunge needle mapping were performed on the hearts. Simulated LDVF was studied in canine hearts to determine the potential role of Purkinje fiber automaticity. ResultsThe mean age at transplant was 48 ± 20 years, and the mean ejection fraction was <20%. The mean cycle length of local activation times on the endocardium was 252 ± 66 ms in SDVF and 441 ± 80 ms in LDVF (p = 0.0002). On the endocardium and the epicardium in LDVF, cycle length was 441 ± 80 ms and 590 ± 88 ms, respectively (p = 0.0002). No endocardial to epicardial activation frequency gradient was seen in SDVF. Simultaneous transmural needle activation was most common in SDVF, whereas endocardial to epicardial activation was most common in LDVF (47.7% and 38.8% of activations, respectively [p = 0.031]). Re-entry was less common in LDVF, and over time, wave break (i.e., nontransmural propagation of wave fronts) developed. Isochronal maps of the left ventricular endocardium in LDVF identified Purkinje potentials as preceding and predominating endocardial activations. In explanted canine heart preparations, rapid pacing led to spontaneous Purkinje fiber activity that was dependent on pacing rate and duration. ConclusionsLDVF in human hearts is characterized by focal endocardial activity with mid-myocardial wave break and not by re-entry. This arrhythmia is modulated by rapid activations in early VF that lead to spontaneous Purkinje fiber activity.