Temporal dynamics of pulmonary response to intravenous histamine in dogs: effects of dose and lung volume

1994 ◽  
Vol 76 (2) ◽  
pp. 616-626 ◽  
Author(s):  
J. H. Bates ◽  
A. M. Lauzon ◽  
G. S. Dechman ◽  
G. N. Maksym ◽  
T. F. Schuessler
Keyword(s):  
Time Course ◽  
Temporal Dynamics ◽  
Oscillation Period ◽  
Recursive Least Squares ◽  
Positive End Expiratory Pressure ◽  
Elastic Recoil ◽  
Ventilation Inhomogeneity ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Time Courses

We measured tracheal pressure (Ptr) and tracheal flow (V) in open-chest anesthetized paralyzed dogs. The lungs were maintained at a fixed volume (initial positive end-expiratory pressure 0.5 kPa) for 80 s while small-amplitude oscillations in V at 1 and 6 Hz were applied simultaneously at the tracheal opening. A bolus of histamine was given intravenously at the start of the oscillation period. The time course of lung elastic recoil pressure (Pel) was obtained by passing a running average over Ptr to smooth out its oscillations. The oscillations themselves were separated into their 1- and 6-Hz components, as were those in V. By fitting models to the 1- and 6-Hz components of Ptr and V by recursive least squares, we obtained time courses of lung resistance at 6 Hz (RL6), dynamic lung elastance at 1 Hz (EL1), and the difference between dynamic lung resistance at 1 and 6 Hz (RL1-RL6). In four dogs we studied the effects of histamine doses of 0.05, 1.0, and 20 mg. We found that Pel increased quickly and plateaued, RL6 continued to increase throughout the oscillation period, and EL1 exhibited features of both Pel and RL6. Furthermore, the ratio of RL1-RL6 to EL1 was qualitatively similar in time course to Pel. We explain these varied time courses in terms of the development of regional ventilation inhomogeneity throughout the lung as the reaction to histamine develops. In four dogs we also studied the effects of reducing the initial positive end-expiratory pressure by 0.25 kPa and found that the changes in RL6, EL1, and RL1-RL6 were greatly magnified, presumably because of the reduced forces of parenchymal interdependence.

scholarly journals Early Visual Cortex Dynamics during Top–Down Modulated Shifts of Feature-Selective Attention

2016 ◽  
Vol 28 (4) ◽  
pp. 643-655 ◽  
Author(s):  
Matthias M. Müller ◽  
Mireille Trautmann ◽  
Christian Keitel
Keyword(s):  
Visual Cortex ◽  
Selective Attention ◽  
Time Course ◽  
Temporal Dynamics ◽  
Behavioral Data ◽  
Coherent Motion ◽  
Neural Dynamics ◽  
Early Visual Cortex ◽  
Time Courses ◽  
Feature Dimension

Shifting attention from one color to another color or from color to another feature dimension such as shape or orientation is imperative when searching for a certain object in a cluttered scene. Most attention models that emphasize feature-based selection implicitly assume that all shifts in feature-selective attention underlie identical temporal dynamics. Here, we recorded time courses of behavioral data and steady-state visual evoked potentials (SSVEPs), an objective electrophysiological measure of neural dynamics in early visual cortex to investigate temporal dynamics when participants shifted attention from color or orientation toward color or orientation, respectively. SSVEPs were elicited by four random dot kinematograms that flickered at different frequencies. Each random dot kinematogram was composed of dashes that uniquely combined two features from the dimensions color (red or blue) and orientation (slash or backslash). Participants were cued to attend to one feature (such as color or orientation) and respond to coherent motion targets of the to-be-attended feature. We found that shifts toward color occurred earlier after the shifting cue compared with shifts toward orientation, regardless of the original feature (i.e., color or orientation). This was paralleled in SSVEP amplitude modulations as well as in the time course of behavioral data. Overall, our results suggest different neural dynamics during shifts of attention from color and orientation and the respective shifting destinations, namely, either toward color or toward orientation.

Estimation of time-varying respiratory mechanical parameters by recursive least squares

1991 ◽  
Vol 71 (3) ◽  
pp. 1159-1165 ◽  
Author(s):  
A. M. Lauzon ◽  
J. H. Bates
Keyword(s):  
Least Squares ◽  
Time Course ◽  
Weighted Average ◽  
Recursive Least Squares ◽  
Dynamic Hyperinflation ◽  
Time Varying ◽  
Mechanical Parameters ◽  
Tracheal Pressure ◽  
The Difference ◽  
Estimation Of Time

Continuous estimation of time-varying respiratory mechanical parameters is required to fully characterize the time course of bronchoconstriction. To achieve such estimation, we developed an estimator that uses the recursive linear least-squares algorithm to fit the equation Ptr = RV + EV + K to measurements of tracheal pressure (Ptr) and flow (V). The volume (V) is obtained by numerical integration of V. The estimator has a finite memory with length into the past at each point in time that varies inversely with the difference between the current measurement of Ptr and that predicted by the model, to allow the algorithm to track rapidly varying parameters (R, E, and K). V usually exhibits significant drift and must be corrected. Of the several correction methods investigated, subtraction of the recursively weighted average of V before integration to V was found to perform best. The estimator was tested on simulated noisy data where it successfully followed a fivefold increase in R and a twofold increase in E occurring over 10 s. Three dogs and two cats were anesthetized, paralyzed, tracheostomized, and challenged with a bolus of methacholine (approximately 13 mg/kg iv). Increases of 3- to 10-fold were observed in R and 2- to 3-fold in E, beginning within 10–40 s after the bolus injection. In some animals we found that the increase in E occurred more slowly than that in R, which the V signal suggested was due to dynamic hyperinflation of the lungs. These results demonstrate that our recursive estimator is able to track rapid changes in respiratory mechanical parameters during bronchoconstrictor challenge.

scholarly journals Spatial distance of target locations affects the time course of both endogenous and exogenous attentional deployment.

2020 ◽  
Author(s):  
Frederik Geweke ◽  
Emilia Pokta ◽  
Viola S. Störmer
Keyword(s):  
Time Course ◽  
Temporal Dynamics ◽  
Spatial Distance ◽  
Exogenous Attention ◽  
Endogenous Attention ◽  
Attentional Deployment ◽  
Current Task ◽  
Time Courses ◽  
Task Goals ◽  
Target Locations

Spatial attention can be deployed exogenously, based on salient events in the environment, or endogenously, based on current task goals. Numerous studies have compared the time courses of these two types of attention, and have demonstrated that exogenous attention is fast and transient and endogenous attention is relatively slow but sustained. In the present study we investigated whether and how the temporal dynamics of exogenous and endogenous attention differ in terms of where attention is deployed in the visual field, in particular at locations nearby or far from fixation. Across a series experiments, we measured attentional shift times for each type of attention, and found overall slower deployment of endogenous relative to exogenous attention, in line with previous research. Importantly, we also consistently found that it takes longer to deploy attention at more distant locations relative to nearby locations, regardless of how attention was instigated. Overall, our results suggest that the temporal limits of attentional deployment across different spatial distances are similar for exogenous and endogenous attention, pointing to shared constraints underlying both attentional modes.

Changes in regional lung impedance after intravenous histamine bolus in dogs: effects of lung volume

1995 ◽  
Vol 78 (3) ◽  
pp. 875-880 ◽  
Author(s):  
Z. Balassy ◽  
M. Mishima ◽  
J. H. Bates
Keyword(s):  
Lung Volume ◽  
Time Course ◽  
Lung Inflation ◽  
Lung Elastance ◽  
Airway Narrowing ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Regional Lung ◽  
Before And After ◽  
Induced Changes

We measured the effect of lung volume on the time course of regional lung input impedance (ZA) after bolus intravenous administration of 2 mg of histamine in seven open-chest dogs using alveolar capsule oscillators. ZA (24–200 Hz) was obtained during apnea at constant lung volume every 2 s for 80 s at lung inflation pressures of 0.1, 0.2, 0.3, 0.5, 0.7, and 1.0 kPa. Local airway resistance (RA) and elastance of the local lung region were calculated by fitting a four-parameter model to the measured ZA. Total lung resistance and lung elastance were also calculated from tracheal pressure and flow measured during mechanical ventilation (0.3 Hz) just before and after each set of ZA measurements. We found the histamine-induced changes in both lung resistance and lung elastance to decrease with increasing lung volume. RA also showed a large negative dependency on lung volume, and the variation between different RA measurements became markedly increased as lung volume decreased. In contrast, local airway elastance was essentially unaffected by lung volume. These results support the idea that parenchymal tethering of the very distal airways impedes their narrowing during bronchoconstriction. They also indicate that reduced parenchymal tethering causes airway narrowing to become markedly more inhomogeneous.

Temporal dynamics of acute isovolume bronchoconstriction in the rat

1997 ◽  
Vol 82 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Jason H. T. Bates ◽  
Thomas F. Schuessler ◽  
Carrie Dolman ◽  
David H. Eidelman
Keyword(s):  
Time Course ◽  
Temporal Dynamics ◽  
Compartment Model ◽  
Significant Degree ◽  
Rate Of Change ◽  
Lung Inflation ◽  
Ventilation Inhomogeneity ◽  
Flow Oscillations ◽  
Three Compartment Model ◽  
Central Airway

Bates, Jason H. T., Thomas F. Schuessler, Carrie Dolman, and David H. Eidelman. Temporal dynamics of acute isovolume bronchoconstriction in the rat. J. Appl. Physiol. 82(1): 55–62, 1997.—The time course of lung impedance changes after intravenous injection of bronchial agonist have produced significant insights into the mechanisms of bronchoconstriction in the dog (J. H. T. Bates, A.-M. Lauzon, G. S. Dechman, G. N. Maksym, and T. F. Shuessler. J. Appl. Physiol. 76: 616–626, 1994). We studied the time course of acute induced bronchoconstriction in five anesthetized paralyzed open-chest rats injected intravenously with a bolus of methacholine. For the 16 s immediately after injection, we held the lung volume constant while applying small-amplitude flow oscillations at 1.48, 5.45, and 19.69 Hz simultaneously, which provided us with continuous estimates of lung resistance (Rl) and elastance (El) at each frequency. This procedure was repeated at initial lung inflation pressures of 0.2, 0.4, and 0.6 kPa. Both Rl and El increased progressively after methacholine administration; however, the rate of change of El increased dramatically as frequency was increased, whereas Rl remained relatively independent of frequency. We interpret these findings in terms of a three-compartment model of the rat lung, featuring two parallel alveolar compartments feeding into a central airway compartment. Model simulations support the notions that both central airway shunting and regional ventilation inhomogeneity developed to a significant degree in our constricted rats. We also found that the rates of increase in both Rl and El were greatly enhanced as the initial lung inflation pressure was reduced, in accord with the notion that parenchymal tethering is an important mechanism limiting the extent to which airways can narrow when their smooth muscle is stimulated to contract.

Acute pulmonary response to intravenous histamine using forced oscillations through alveolar capsules in dogs

1994 ◽  
Vol 77 (5) ◽  
pp. 2140-2148 ◽  
Author(s):  
M. Mishima ◽  
Z. Balassy ◽  
J. H. Bates
Keyword(s):  
Time Course ◽  
Forced Oscillations ◽  
Bolus Administration ◽  
Positive End Expiratory Pressure ◽  
Pressure System ◽  
Pulmonary Response ◽  
Lung Compartment ◽  
Lung Resistance ◽  
Baseline Values ◽  
The Times

We measured the time course of alveolar input impedance using two alveolar capsule oscillators after intravenous bolus administration of 20 mg of histamine in open-chest dogs. Impedances (24–200 Hz) were obtained every 2 s after an injection for 100 s. Each impedance was fit with a model consisting of a pathway (with resistance and inertance) leading from the alveolar capsule into a subpleural region (with elastance EA) that, in turn, was connected to the lung compartment (consisting of the remainder of the lung and positive end expiratory pressure system) via another pathway (with resistance RA). In all cases (6 dogs, 2 capsules each), the resistance and inertance leading from the alveolar capsules were negligible. The correlation of the relative increases in RA obtained from the two capsule oscillators in each dog was not significant. The correlation for EA also was not significant. The times at which RA achieved values of 20% greater than baseline were not significantly correlated between the two capsules, as was the case for EA. However, the baseline values of EA and RA from a given capsule were significantly correlated, as were their fractional increases with histamine. These results show that both the magnitude and timing of changes in local lung resistance and elastance are spatially extremely heterogeneous.

scholarly journals Canonical EEG Microstate Dynamic Properties and Their Associations with fMRI Signals at Resting Brain

2020 ◽  
Author(s):  
Obada Al Zoubi ◽  
Masaya Misaki ◽  
Aki Tsuchiyagaito ◽  
Ahmad Mayeli ◽  
Vadim Zotev ◽  
...  
Keyword(s):  
Functional State ◽  
Emotional Processing ◽  
Time Course ◽  
Temporal Dynamics ◽  
Dynamic Properties ◽  
Mental Illnesses ◽  
Hemodynamic Response Function ◽  
Functional Interpretation ◽  
Fmri Signal ◽  
Time Courses

AbstractElectroencephalography microstates (EEG-ms) capture and reflect the spatio-temporal neural dynamics of the brain. A growing literature is employing EEG-ms-based analyses to study various mental illnesses and to evaluate brain mechanisms implicated in cognitive and emotional processing. The spatial and functional interpretation of the EEG-ms is still being investigated. Previous works studied the association of EEG-ms time courses with blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal and suggested an association between EEG-ms and resting-state networks (RSNs). However, the distinctive association between EEG-ms temporal dynamics and brain neuronal activities is still not clear, despite the assumption that EEG-ms are an electrophysiological representation of RSNs activity. Recent works suggest a role for brain spontaneous EEG rhythms in contributing to and modulating canonical EEG-ms topographies and determining their classes (coined A through D) and metrics. This work simultaneously utilized EEG and fMRI to understand the EEG-ms and their properties further. We adopted the canonical EEG-ms analysis to extract three types of regressors for EEG-informed fMRI analyses: EEG-ms direct time courses, temporal activity per microstate, and pairwise temporal transitions among microstates (the latter two coined activity regressors). After convolving EEG-ms regressors with a hemodynamic response function, a generalized linear model whole-brain voxel-wise analysis was conducted to associate EEG-ms regressors with fMRI signals. The direct time course regressors replicated prior findings of the association between the fMRI signal and EEG-ms time courses but to a smaller extent. Notably, EEG-ms activity regressors were mostly anticorrelated with fMRI, including brain regions in the somatomotor, visual, dorsal attention, and ventral attention fMRI networks with no significant overlap for default mode, limbic or frontoparietal networks. A similar pattern emerged in using the transition regressors among microstates but not in self-transitions. The relatively short duration of each EEG-ms and the significant association of EEG-ms activity regressors with fMRI signals suggest that EEG-ms manifests successive transition from one brain functional state to another rather than being associated with specific brain functional state or RSN networks.

scholarly journals Hierarchical representation of multi-step tasks in multiple-demand and default mode networks

2019 ◽  
Author(s):  
Tanya Wen ◽  
John Duncan ◽  
Daniel J Mitchell
Keyword(s):  
Time Course ◽  
Temporal Dynamics ◽  
Representational Content ◽  
Brain Regions ◽  
Neural Representation ◽  
Step Response ◽  
Default Mode ◽  
Task Identity ◽  
Level Information ◽  
Time Courses

AbstractTask episodes consist of sequences of steps that are performed to achieve a goal. We used fMRI to examine neural representation of task identity, component items, and sequential position, focusing on two major cortical systems – the multiple-demand (MD) and default mode networks (DMN). Human participants (20 male, 22 female) learned six tasks each consisting of four steps. Inside the scanner, participants were cued which task to perform and then sequentially identified the target item of each step in the correct order. Univariate time-course analyses indicated that intra-episode progress was tracked by a tonically increasing global response, plus an increasing phasic step response specific to MD regions. Inter-episode boundaries evoked a widespread response at episode onset, plus a marked offset response specific to DMN regions. Representational similarity analysis was used to examine encoding of task identity and component steps. Both networks represented the content and position of individual steps, but the DMN preferentially represented task identity while the MD network preferentially represented step-level information. Thus, although both DMN and MD networks are sensitive to step-level and episode-level information in the context of hierarchical task performance, they exhibit dissociable profiles in terms of both temporal dynamics and representational content. The results suggest collaboration of multiple brain regions in control of multi-step behavior, with MD regions particularly involved in processing the detail of individual steps, and DMN adding representation of broad task context.Significance StatementAchieving one’s goals requires knowing what to do and when. Tasks are typically hierarchical, with smaller steps nested within overarching goals. For effective, flexible behavior, the brain must represent both levels. We contrast response time-courses and information content of two major cortical systems – the multiple-demand (MD) and default mode networks (DMN) – during multi-step task episodes. Both networks are sensitive to step-level and episode-level information, but with dissociable profiles. Intra-episode progress is tracked by tonically increasing global responses, plus MD-specific increasing phasic step responses. Inter-episode boundaries evoke widespread responses at episode onset, plus DMN-specific offset responses. Both networks encode content and position of individual steps, but the DMN and MD networks favor task identity and step-level information respectively.

scholarly journals Enumerating the forest before the trees: The time courses of estimation-based and individuation-based numerical processing

2020 ◽  
Author(s):  
David Melcher ◽  
Christoph Huber-Huber ◽  
Andreas Wutz
Keyword(s):  
Temporal Resolution ◽  
Time Course ◽  
Temporal Dynamics ◽  
Estimation Accuracy ◽  
Object Individuation ◽  
Capacity Limits ◽  
Preattentive Processing ◽  
Ensemble Perception ◽  
Subitizing Range ◽  
Time Courses

Abstract Ensemble perception refers to the ability to report attributes of a group of objects, rather than focusing on only one or a few individuals. An everyday example of ensemble perception is the ability to estimate the numerosity of a large number of items. The time course of ensemble processing, including that of numerical estimation, remains a matter of debate, with some studies arguing for rapid, “preattentive” processing and other studies suggesting that ensemble perception improves with longer presentation durations. We used a forward-simultaneous masking procedure that effectively controls stimulus durations to directly measure the temporal dynamics of ensemble estimation and compared it with more precise enumeration of individual objects. Our main finding was that object individuation within the subitizing range (one to four items) took about 100–150 ms to reach its typical capacity limits, whereas estimation (six or more items) showed a temporal resolution of 50 ms or less. Estimation accuracy did not improve over time. Instead, there was an increasing tendency, with longer effective durations, to underestimate the number of targets for larger set sizes (11–35 items). Overall, the time course of enumeration for one or a few single items was dramatically different from that of estimating numerosity of six or more items. These results are consistent with the idea that the temporal resolution of ensemble processing may be as rapid as, or even faster than, individuation of individual items, and support a basic distinction between the mechanisms underlying exact enumeration of small sets (one to four items) from estimation.

scholarly journals Pseudo-streaming potentials in Necturus gallbladder epithelium. II. The mechanism is a junctional diffusion potential.

1992 ◽  
Vol 99 (3) ◽  
pp. 317-338 ◽  
Author(s):  
L Reuss ◽  
B Simon ◽  
C U Cotton
Keyword(s):  
Time Course ◽  
Bathing Solution ◽  
Intercellular Spaces ◽  
Similar Time ◽  
Streaming Potentials ◽  
Osmotic Water ◽  
Lateral Intercellular Spaces ◽  
Transepithelial Voltage ◽  
Time Courses ◽  
Good Agreement

The mechanisms of apparent streaming potentials elicited across Necturus gallbladder epithelium by addition or removal of sucrose from the apical bathing solution were studied by assessing the time courses of: (a) the change in transepithelial voltage (Vms). (b) the change in osmolality at the cell surface (estimated with a tetrabutylammonium [TBA+]-selective microelectrode, using TBA+ as a tracer for sucrose), and (c) the change in cell impermeant solute concentration ([TMA+]i, measured with an intracellular double-barrel TMA(+)-selective microelectrode after loading the cells with TMA+ by transient permeabilization with nystatin). For both sucrose addition and removal, the time courses of Vms were the same as the time courses of the voltage signals produced by [TMA+]i, while the time courses of the voltage signals produced by [TBA+]o were much faster. These results suggest that the apparent streaming potentials are caused by changes of [NaCl] in the lateral intercellular spaces, whose time course reflects the changes in cell water volume (and osmolality) elicited by the alterations in apical solution osmolality. Changes in cell osmolality are slow relative to those of the apical solution osmolality, whereas lateral space osmolality follows cell osmolality rapidly, due to the large surface area of lateral membranes and the small volume of the spaces. Analysis of a simple mathematical model of the epithelium yields an apical membrane Lp in good agreement with previous measurements and suggests that elevations of the apical solution osmolality elicit rapid reductions in junctional ionic selectivity, also in good agreement with experimental determinations. Elevations in apical solution [NaCl] cause biphasic transepithelial voltage changes: a rapid negative Vms change of similar time course to that of a Na+/TBA+ bi-ionic potential and a slow positive Vms change of similar time course to that of the sucrose-induced apparent streaming potential. We conclude that the Vms changes elicited by addition of impermeant solute to the apical bathing solution are pseudo-streaming potentials, i.e., junctional diffusion potentials caused by salt concentration changes in the lateral intercellular spaces secondary to osmotic water flow from the cells to the apical bathing solution and from the lateral intercellular spaces to the cells. Our results do not support the notion of junctional solute-solvent coupling during transepithelial osmotic water flow.

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