Distribution Of Interpulse Intervals Research Articles

Elementary integrate-and-fire process underlies pulse amplitudes in Electrodermal activity.

Electrodermal activity (EDA) is a direct read-out of sweat-induced changes in the skin’s electrical conductance. Sympathetically-mediated pulsatile changes in skin sweat measured as EDA resemble an integrate-and-fire process, which yields an inverse Gaussian model as the inter-pulse interval distribution. We have previously showed that the inter-pulse intervals in EDA follow an inverse Gaussian distribution. However, the statistical structure of EDA pulse amplitudes has not yet been characterized based on the physiology. Expanding upon the integrate-and-fire nature of sweat glands, we hypothesized that the amplitude of an EDA pulse is proportional to the excess volume of sweat produced compared to what is required to just reach the surface of the skin. We modeled this as the difference of two inverse Gaussian models for each pulse, one which represents the time required to produce just enough sweat to rise to the surface of the skin and one which represents the time requires to produce the actual volume of sweat. We proposed and tested a series of four simplifications of our hypothesis, ranging from a single difference of inverse Gaussians to a single simple inverse Gaussian. We also tested four additional models for comparison, including the lognormal and gamma distributions. All models were tested on EDA data from two subject cohorts, 11 healthy volunteers during 1 hour of quiet wakefulness and a different set of 11 healthy volunteers during approximately 3 hours of controlled propofol sedation. All four models which represent simplifications of our hypothesis outperformed other models across all 22 subjects, as measured by Akaike’s Information Criterion (AIC), as well as mean and maximum distance from the diagonal on a quantile-quantile plot. Our broader model set of four simplifications offered a useful framework to enhance further statistical descriptions of EDA pulse amplitudes. Some of the simplifications prioritize fit near the mode of the distribution, while others prioritize fit near the tail. With this new insight, we can summarize the physiologically-relevant amplitude information in EDA with at most four parameters. Our findings establish that physiologically based probability models provide parsimonious and accurate description of temporal and amplitude characteristics in EDA.

Point process temporal structure characterizes electrodermal activity

Electrodermal activity (EDA) is a direct readout of the body's sympathetic nervous system measured as sweat-induced changes in the skin's electrical conductance. There is growing interest in using EDA to track physiological conditions such as stress levels, sleep quality, and emotional states. Standardized EDA data analysis methods are readily available. However, none considers an established physiological feature of EDA. The sympathetically mediated pulsatile changes in skin sweat measured as EDA resemble an integrate-and-fire process. An integrate-and-fire process modeled as a Gaussian random walk with drift diffusion yields an inverse Gaussian model as the interpulse interval distribution. Therefore, we chose an inverse Gaussian model as our principal probability model to characterize EDA interpulse interval distributions. To analyze deviations from the inverse Gaussian model, we considered a broader model set: the generalized inverse Gaussian distribution, which includes the inverse Gaussian and other diffusion and nondiffusion models; the lognormal distribution which has heavier tails (lower settling rates) than the inverse Gaussian; and the gamma and exponential probability distributions which have lighter tails (higher settling rates) than the inverse Gaussian. To assess the validity of these probability models we recorded and analyzed EDA measurements in 11 healthy volunteers during 1 h of quiet wakefulness. Each of the 11 time series was accurately described by an inverse Gaussian model measured by Kolmogorov-Smirnov measures. Our broader model set offered a useful framework to enhance further statistical descriptions of EDA. Our findings establish that a physiologically based inverse Gaussian probability model provides a parsimonious and accurate description of EDA.

Background firing in the auditory midbrain of the frog

Statistical characteristics of background firing in the midbrain auditory units of grass frog (Rana t. temporaria) located in torus semicircular (TS) were investigated. Only about 5% of the cells demonstrated prominent spontaneous firing. For such units the following characteristics were obtained: the distribution of interpulse intervals, the autocorrelation functions (ACF) for the real firing process and for the process with shuffled intervals, the hazard function (HF) and the joint distribution of adjacent interpulse intervals. The burstiness of firing was also estimated. In the absolute majority of the cells, the background firing demonstrated considerable deviation from the renewal process. There was weak but significant positive correlation between adjacent interpulse intervals. The burstiness of firing in the midbrain auditory units was moderate but higher than reported for medullary auditory neurons. The value of burstiness did not decrease after interval shuffling. Along with the reduction in excitability (generalized refractoriness) in many neurons observed post-spike facilitation effects were observed. Comparing background activity in medullary and midbrain nucleus suggests that there is an increase in complexity of the information processing along the auditory pathway.

Reflection of the State of Hunger in Impulse Activity of Nose Wing Muscles and Upper Esophageal Sphincter during Search behavior in Rabbits.

Reflection of the state of hunger in impulse activity of nose wing muscles and upper esophageal sphincter muscles was studied in chronic experiments on rabbits subjected to 24-h food deprivation in the absence of locomotion and during search behavior. In the absence of apparent behavioral activity, including sniffing, alai nasi muscles of hungry rabbits constantly generated bursts of action potentials synchronous with breathing, while upper esophageal sphincter muscles exhibited regular aperiodic low-amplitude impulse activity of tonic type. Latent form of food motivation was reflected in the structure of temporal organization of impulse activity of alai nasi muscles in the form of bimodal distribution of interpulse intervals and in temporal structure of impulse activity of upper esophageal sphincter muscles in the form of monomodal distribution. The latent form of food motivation was manifested in the structure of temporal organization of periods of the action potentials burst-like rhythm, generated by alai nasi muscles, in the form of monomodal distribution, characterized by a high degree of dispersion of respiratory cycle periods. In the absence of physical activity hungry animals sporadically exhibited sniffing activity, manifested in the change from the burst-like impulse activity of alai nasi muscles to the single-burst activity type with bimodal distribution of interpulse intervals and monomodal distribution of the burst-like action potentials rhythm periods, the maximum of which was shifted towards lower values, which was the cause of increased respiratory rate. At the same time, the monomodal temporal structure of impulse activity of the upper esophageal sphincter muscles was not changed. With increasing food motivation in the process of search behavior temporal structure of periods of the burst-like action potentials rhythm, generated by alai nasi muscles, became similar to that observed during sniffing, not accompanied by animal's locomotion, which is typical for the increased respiratory rhythm frequency. Increased hunger motivation was reflected in the temporal structure of impulse activity of upper esophageal sphincter muscles in the form of a shift to lower values of the maximum of monomodal distribution of interpulse intervals on the histogram, resulting in higher impulse activity frequency. The simultaneous increase in the frequency of action potentials bursts generation by alai nasi muscles and regular impulse activity of upper esophageal sphincter muscles is a reliable criterion for enhanced food motivation during search behavior in rabbits.

On the existence of spontaneous neuronal bursting activity at the periphery of the amphibian auditory pathway

The firing activity of 104 neurons from the medullar dorsal nucleus (homologous to the mammalian cochlear nucleus complex) of immobilized common frogs (Rana t. temporaria) was recorded extracellularly in the absence of external auditory stimuli. This background activity was analyzed by using stochastic point process parameters such as the coefficient of variation, local coefficient of variation, interdependence of neighboring intervals, interpulse interval distribution, autocorrelation, and hazard function. All these parameters were put in correspondence with bursting rate, i.e., relative number of interpulse intervals grouped in clusters, or bursts, determined by the proposed method. Neurons with pronounced refractoriness, as a rule, exhibited lower bursting rates whereas neurons with a distinct maximum of the correlation function showed higher values than expected from a random Poisson process. However, even in the latter group of cells, bursting rates usually did not decrease after random shuffling of all the interpulse intervals. As a result, we must admit the absence of clustered spontaneous activity in second-order auditory neurons in the amphibian species studied. These data are compared with the specificities of spontaneous firing activity in different parts of the mammalian auditory pathway.

Microphone-Array Tracking of Echolocating Bats Foraging in the Field

Microphone-Array Tracking of Echolocating Bats Foraging in the Field

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the mylohyoid muscle in rabbits under conditions of hunger and satiety

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of mylohyoid muscle were studied in chronic experiments under conditions of hunger and satiety. Threshold stimulation of the lateral hypothalamus in starving and satiated rabbits in the absence of food induced searching behavior associated with burst-like impulse activity with a bimodal distribution of interpulse intervals. Regular spike burst in the mylohyoid muscle during stimulation of the lateral hypothalamus in the absence of food serves as an example of the anticipatory type reaction. Increased food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with food offered led to successful food-procuring behavior, during which the frequency of spike bursts in the mylohyoid muscle became comparable with that under conditions of natural foraging behavior stimulated by the need in nutrients. Our results suggest that temporal structure of mylohyoid muscle impulse activity reflects convergent interactions of food-motivation excitation with reinforcement excitation on neurons of the masticatory and deglutitive centers.

Effects of Electrical Stimulation of the Hunger Center in the Lateral Hypothalamus and Food Reinforcement on Impulse Activity of the Proper Masticatory Muscle in Rabbits under Conditions of Hunger and Satiation

Threshold stimulation of the lateral hypothalamus in starving and preliminary fed (satiated) rabbits in the absence of feed induces searching behavior associated with burst-like impulse activity of proper masticatory muscle with a bimodal distribution of interpulse intervals, what represents an anticipatory type of reaction. The increase in the level of food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with the food offered led to successful food-procuring behavior, during which the frequency and amplitude of spike bursts in the proper masticatory muscle become comparable with those under conditions of natural foraging behavior stimulated by the need in nutrients. Motivational excitation and backward afferentation from food reward are addressed to the same neurons of the masticatory center in the medulla oblongata.

Hunger and Satiation in the Structure of Temporal Organization of Impulse Activity of Masticatory Muscles in Rabbits

Impulse activity of masticatory muscles, jaw elevators and depressors, during hunger, eating, and satiation was studied in chronic experiments on rabbits. The state of hunger is specifically reflected in the structure of temporal organization of impulse activity of proper masticatory muscles as a monomodal distribution of interpulse intervals and in activity of the mylohyoid muscle as bimodal distributions. Food intake induces reorganization of the temporal structure of impulse activity in both muscles manifesting in the form of similar bimodal patterns of distributions of interpulse intervals.

Another turn for p53

Another turn for p53

Discrimination of individually characteristic electric organ discharges by a weakly electric fish

Waveform analysis of the electric organ discharges (EODs) of the weakly electric fish Gymnotus carapo found significant variation between individuals but little variation in EODs from the same individual. That is, EOD waveforms are individually distinctive. A playback experiment obtained results that were comparable to those used to infer neighbour recognition in other territorial species. These two results show that the electric signals of this species of weakly electric fish have individually distinctive variation and that individual variation can be perceived by the fish, independently of possible cues contained within the inter-pulse interval distribution. This is the first time that individual discrimination has been demonstrated in any species of electric fish.

Bottlenose dolphin (Tursiops truncatus): Difference in the pattern of interpulse intervals

When the echolocation detection abilities of a beluga whale and a bottlenose dolphin were tested on identical cylindrical targets and distances, they had interpulse interval (IPI) distributions which were different, while detection accuracy showed no significant difference. Bottlenose dolphin pulse trains show a predictable and systematic relationship between the distance to a detected target and time between echolocation pulses, thus permitting an inference of attending distance [R. H. Penner and J. Kadane, J. Acoust. Soc. Am. Suppl. I 68, S97 (1980)]. The beluga whale pulse trains contained, at all target distances, a first IPI component starting around 30 ms and increasing to 60 ms and a second IPI component between 200 to 220 ms which became more numerous as target distance increased. The transition zone between the first and second components contained very few interval counts. The interpulse intervals within the transition zone increased as target distance increased. If the bottlenose dolphin IPI patterns are accepted as models, and similar assumptions regarding attending distance are applied to the beluga whale pulse train, the picture is one of always scanning out to 30 m; followed by short scan out to 160 m. Subsequent target detection work using spheres instead of cylinders as targets, showed the same IPI distribution patterns for the beluga whale.

Probability gate statistics

A probability gate presents a fixed but controllable transmission probability p to pulses arriving at its input. This paper describes some statistical properties of the transformation imposed by a gate on the input distribution of interpulse intervals. The output distribution of interpulse intervals is derived in terms of the input density and p. A simple relation is shown to hold between the moment generating functions, and the first four output moments are presented in terms of the input moments and p. Certain restrictions on the kinds of obtainable output distributions are discussed. In particular, a condition is established that specifies when the output density is a “replica” of the input distribution.

Letter to the Editor: Interpulse Interval Distribution in the Environment of N Periodic Radars

Letter to the Editor: Interpulse Interval Distribution in the Environment of N Periodic Radars