Trains Of Bursts Research Articles

Acoustic properties and geographic variation in the vibratory courtship signals of the european chloropid fly,Lipara lucens meigen (Diptera, Chloropidae)

Geographic variation in courtship vibratory signals inLipara lucens from 7 disjunctive European populations were examined. Simple female responding signals showed significant interlocal difference in the pulse-group intervals only in the English population. More differentiated male courtship signals were separated into anterior “preliminary vibration” and posterior “main vibration”. The latter, composed of a train of bursts, showed significant differences among populations in the number of pulses in a burst, burst duration (BD), burst interval (BI) and burst period (BP). Latvian, Hungarian and Bulgarian populations had more pulses in a burst than those of E. Germany, Belgium, Czechoslovakia and England. Latvian and Bulgarian populations showed significantly larger values of BD, whereas that of Belgium showed a significantly smaller value. BI in the English population had the smallest value, and those in the Latvian and Bulgarian populations had the longest values. No significant differences were observed in BD and BI between E. Germany, Czechoslovakia and Hungary. Multivariate statistic analyses on the time-amplitude variables of the male signals showed uniqueness in the Belgian, English, Latvian and Bulgarian populations. Genetic background of the geographic variations in the vibratory signals are discussed in this context.

Some temporal effects on the sensitivity of the CAP to changes in sound intensity and frequency

The sensitivity of the compound action potential (CAP) of the auditory nerve to changes in sound intensity and frequency was obtained in anesthetized Mongolian gerbils. Detection of the change in N1 peak magnitude caused by a probe stimulus was determined using a two‐interval tracking procedure [E. M. Relkin and R. L. Smith, J. Acoust. Soc. Am. Suppl. 1 83, S98 (1988)], a technique that depends on both the N1 magnitude and its variability. The probe was added to a background sound consisting of a train of short tone bursts, and the time delay from background onset to probe onset was varied. Adaptation, i.e., the number of prior tone bursts, reduced the magnitude and variability of the CAP in response to successive background tone bursts, but did not appear to directly affect detection of the probe tone. However, detection was found to be a sensitive function of the latency between the onset of the probe and the corresponding background tone burst, particularly for probes that differed in frequency from the background. This dependency apparently resulted from variations in neural synchrony caused by cochlear travel time. [Research sponsored by NSF and NIH.]

An interactive toolset for characterizing complex neural systems

A set of two computer programs is described which enable the following functions: 1. (1) High-speed data acquisition from up to eight recording channels with presentation of uniform or quasi-random stimulus trains on one or two stimulus channels. 2. (2) On-line computation and display of averaged responses on all recording channels evoked by both stimulus channels. 3. (3) Computation and display of averaged evoked potentials and functional power series (FPS) through third order for characterization of system nonlinearities. 4. (4) Computation and display of stimulated responses to arbitrarily selected stimulus trains using a previously computed FPS. Both programs are implemented in FORTRAN, include on-line help, interactive and batch processing facilities and produce extensive graphics output according to the Tektronix 4010 protocol. Their initial implementation was on an LSI-II microcomputer using TSX + extensions to RT11. Additional capabilities and speed have been gained by porting the analysis routine to the Apollo workstation environment. To date these programs have been used to study the following: 1. (1) The somatosensory system in the human using dual random trains presented to the median and ulnar nerves. 2. (2) Cognitive processing in the human (normals and first-break schizophrenics) using both uniform (P300 paradigm) and dual random trains of tone bursts with the subject either counting or pressing a lever in response to tones with a specific pitch. 3. (3) The network properties of the rabbit hippocampus (both in vivo and in vitro preparations) using random train simulation of the intrinsic pathways.

CW and pulse Doppler diagnostic system

In an interlaced pulse-echo and range-gated Doppler system, an ultrasound transmitter generates a train of constant repetition rate echo pulse interlaced with a Doppler pulse train of plural bursts. The time duration between each burst and the preceding range gate opening is held constant while the time to the successive range gate opening is automatically varied to provide a continuously variable PRF tracking of the console range gate depth setting. The power of the transmitted signal is internally varied in the same sense and the cutoff frequency of the receiver low pass tracking filters is varied in the opposite sense to optimize signal-to-noise ratio at various tissue inspection depths. Selectable turnable high pass filters normalized to low velocity roll-off eliminate artifact for peripheral or central vascular probes. The detection system operates in quadrature and includes a synchronous demodulator and a peak detector, and a level detector operative on peak detected signals. Transducer probes interchangeably usable in the system include within each probe a narrow band amplifier critically turned to the respective probe crystal to provide further S/N ratio improvement. The system is operable in CW or pulsed Doppler modes dependent on switch setting on the split crystal probe.

Commissural synapses, but not mossy fiber synapses, in hippocampal field CA3 exhibit associative long-term potentiation and depression

When CA3 commissural afferents received low-frequency (weak) stimuli synchronized with a train of mossy fiber bursts (strong), associative long-term potentiation (LTP) was induced at mixed commissural and associational synapases on hippocampal CA3 pyramidal cells in vitro. In contrast, a weak mossy fiber input did not potentiate when given in phase with commissural/associational bursts. Furthermore, commissural/associational synapses receiving low-frequency stimuli out-of-phase with strong rhythmic mossy fiber input showed associative long-term depression (LTD), whereas mossy fiber synaptic strengths were not depressed when they received weak inputs out-of-phase with a strong commissural/associational input. Thus, both associative LTP and associative LTD can be induced at commissural/associational synapses, but not at mossy fiber synapses.

Tuning curve widths of infants and adults in simultaneous and nonsimultaneous masking

Tuning curve widths were estimated using the pulsation threshold (PT) technique for infants, 6‐month‐olds, and adults. The observer‐based psychoacoustic procedure [L. W. Olsho et al., Dev. Psychol., in press (1987)] was the test procedure. Listeners discriminated a train of alternating masker and probe tone bursts from a train of masker tone bursts presented with a continuous probe tone. These stimuli were presented in a background of broadband noise at 20‐dB pressure spectrum level. The probe level was 10 dB SL. PTs were obtained at the tuning curve tip and at two points, one above and one below the probe frequency, 10 dB above the tip. The resulting Q10s were compared to those obtained in simultaneous masking for 6‐month‐olds and adults [L. W. Olsho, Inf. Behav. Dev. 8, 371–384 (1985)]. Adult Q10s were significantly greater for PT tuning curves at 500, 1000, and 4000 Hz. Infant PT Q10s were significantly greater than simultaneous masking Q10s at 500 and 1000 Hz, but not at 4000 Hz. [Work supported by NIH.]

Modulation of spontaneous myometrial activity in chronically instrumented ovariectomized sheep.

The uterine electromyogram (EMG) and intrauterine pressure curves (IUP) were investigated as indicators of myometrial activity in chronically instrumented, ovariectomized ewes. Spontaneous electrical activity was characterized by rhythmic patterns of trains of bursts accompanied by IUP waves. Administration of adrenergic (propranolol or phentolamine) or cholinergic (atropine) blocking agents had no effect on spontaneous uterine activity. Both oxytocin and PGF2 alpha appeared to stimulate spontaneous myometrial activity. 17beta-Estradiol temporarily depressed uterine activity in a dose-dependent fashion. The period of relaxation was followed by a pronounced increase in activity. Progesterone treatment resulted in long-term suppression of myometrial activity. Oxytocin and PGF2alpha increased EMG and IUP activity during estradiol suppression but not after progesterone treatment. These results indicate that the myometrium is active in chronically instrumented, ovariectomized ewes. The autonomic nervous system or its receptors do not play a role in the maintenance of spontaneous myometrial activity, estradiol and progesterone suppress myometrical activity but by different mechanisms.

The rapid burster activity observed from tenma

The Japanese X-ray astronomy satellite Hakucho and Tenma observed the activity of the rapid burster MXB 1730-335 in 1979 and 1983. In the first observation from 8 to 22 August 1979, the activity began with rapidly repetitive type II bursts which are similar to those observed earlier. Then the energy per burst quickly increased and evolved to exhibit a long flat top or roughly trapezoidal shape. In the last phase, burst size became smaller and the activity returned to the short type II burst mode. In the second observation from 5 to 31 August 1983, the burster started to emit a train of bursts which aparently resemble to type I bursts with quasi-periodical occurrence of 74 ∼ 90 minutes. In the second phase, there appeared long type II bursts of trapezoidal profiles and exotic long bursts. In the last phase, about 3000 rapidly repetitive short type II bursts were observed. The bursts with shortest intervals exhibited almost periodic features of 16 sec. The type II bursts in both observation evolved to the size E of ∼ 6 × 10 40 erg that is one order larger than ever observed. They were long bursts ( τ ≦ 600 s) of flat topped (trapezoidal) shape and those of exotic profiles. Those type II bursts exhibited some kinds of quasi-periodicities, which implies the vibrations or instabilities of the mass accretion onto the neutron stars. The type I bursts were often observed with/without type II bursts.

Temporal discrimination in the goldfish.

The capacities of the goldfish to detect changes in sound burst repetition rate were studied using classical respiratory conditioning. In experiment I, the just detectable amount of an instantaneous random jitter of burst period was measured as a function of mean period. In experiment II, the just detectable amount of slow sinusoidal jitter of burst period was measured for three burst types having different spectral and waveform characteristics. In experiment III, sinusoidal jitter detection thresholds were measured in the presence of varying degrees of random jitter. The data show that (1) rms sinusoidal and random jitter in a periodic train of bursts are approximately equally detectable. (2) Sinusoidal jitter detection depends upon burst period duration and the short-term envelope definition and not upon frequency-domain information. (3) For a given burst period, stimulus jitter and an internal temporal noise appear to add independently to determine period discriminability. (4) Psychophysical estimates of internal temporal noise are 0.160 and 0.710 msec at periods of 5 and 10 msec, respectively. The data are consistent with the hypothesis that the burst period discrimination task is based upon a measurement of the time interval (duration) between spikes in auditory neurons.

Habituation and rate effect in the auditory cortical potentials evoked by trains of stimuli

The effects of the stimulus repetition rate over the habituated auditory cortical evoked responses were studied. The stimulation pattern consisted of trains of pure tone bursts with interstimulus interval (ISI) of 1 s, and intertrain interval (ITI) of 5 s, delivered with constant time and intensity parameters during 93 min. The analysis of the responses was based upon across averaging of the trains, each single response being evaluated in the latency and amplitude parameters. Two time-dependent factors affected the responses in a distinct way: the habituation throughout the whole stimulation and the rate effect within the train. The linear regressions of the time/amplitude functions of the responses were calculated in relation to the duration of ISI and ITI. By introducing a correction factor depending on the repetition rate it was possible to evaluate the relationships between habituation and repetition rate. Changes in the repetition rate do not have any effect on the habituation process. The two phenomena are completely distinct, and they probably have neurophysiologic substances corresponding to different levels in the central nervous system (CNS).

Suppression of simple spike discharges of cerebellar Purkinje cells by impulses in climbing fibre afferents

Electrical stimulation has been used to activate climbing fibres (CFs) projecting to the cat cerebellar cortex, and the effects of low frequency (up to 10 Hz) trains of CF inputs on the discharges of cerebellar cortical neurones has been examined. Repetitive activation of the CF innervating a Purkinje (P) cell could reduce or completely suppress the ongoing simple spike discharges (SS) of the P cell. Suppression of SS was very readily produced by trains of short bursts of impulses in the CF. SS could remain suppressed for up to 4 min after such a train of CF impulses. Recordings obtained from Golgi, basket and granule cells indicated that these cortical neurones did not mediate the suppression. It is proposed that the SS are suppressed as the result of a direct action of CF impulses on the P cell's dendritic tree which blocks the ongoing transmission of excitation from parallel fibres.

Measurements of the artificially stimulated precipitation of electrons from the inner radiation belt in the experiment “SPOLOKH-2”

Evidence for an enhancement of the electron flux associated with a barium chaped charge release from “SPOLOKH-2” rocket payload, launched from Volgograd (L = 2.2) on June 29, 1978, will be presented. There is also evidence for a periodic train of particle bursts occurring with about 11 second period during more than 100 seconds after the release. The observed phenomena is interpreted as a “trigger-effect”.

A model of the rapid burster

A new burst mode of MXB 1730 - 335, the rapid burster, as discovered by Hakucho in August 1979, is characterized by a train of long X-ray bursts whose behaviour is dictated by the accretion rate. In this mode the burst luminosity reaches the Eddington limit, so that the X-ray pressure controls the accretion from a reservoir in the magnetopause and accretion columns in the polar regions explain general features of the rapid burster observed in August 1979.

Control of multiple impulse-initiation sites in a leech interneuron.

1. Several heart interneurons (HN cells) of the leech nerve cord have impulse-initiation sites in every segmental ganglion through which their single axons pass. All these initiation sites are capable of producing rhythmic impulse bursts. However, under normal conditions a dominant primary initiation site in the ganglion where the cell body is located suppresses the activity of the other secondary sites. 2. Hyperpolarization of the primary initiation site by injected current permits immediate expression of rhythmic activity by a secondary site, usually the one located in the next posterior ganglion. 3. The free-running impulse burst rhythm of the primary site is stronger than that of the secondary site, having a greater burst duration and a tendency toward a higher burst frequency. 4. Bursts of primary-site impulses intercalated into the secondary-site impulse burst rhythm have a twofold effect. First, early to midway through the secondary-site's burst cycle, they phase delay its impulse burst rhythm. Second, early in the secondary-site's burst cycle, they tend to suppress ongoing impulse bursts, and late in the secondary-site's burst cycle, they tend to suppress the next expected impulse burst. The amount of burst suppression seen early and late in the secondary-site burst cycle depends on the burst duration and intraburst impulse frequency of the intercalated burst. 5. The ability of a train of primary-site impulse bursts to completely suppress secondary-site activity depends on burst duration, intraburst impulse frequency, and burst period. 6. Primary-site impulse trains with burst parameters close to those of naturally occurring primary-site bursts completely suppress secondary-site activity. 7. These results are consistent with the notion that the primary-site impulse burst rhythm of an HN cell suppresses the activity of its secondary site because, cycle by cycle, it delays and/or suppresses the next secondary-site burst so that no secondary-site bursts are produced. Dominance of the primary site over the secondary site is ensured by virtue of the primary-site's stronger impulse burst rhythm.

Trigger, An active release experiment that stimulated auroral particle precipitation and wave emissions

Models of auroral processes have been advanced in which the ionosphere plays an active role in stimulating auroral particle precipitation. The validity of these suggestions can be investigated by releasing an artificial plasma cloud into the ionosphere and studying the effects. To this end, the sounding rocket experiment Trigger, comprising a diagnostic and a chemical release payload, was conducted. As a consequence of the release, a drastic increase of the field‐aligned charged particle flux was observed over the approximate energy range 10 eV to more than 300 keV, starting about 150 ms after the release and lasting about 1 s. There is also evidence of a second particle burst, starting 1 s after the release and lasting for tens of seconds. In addition, there is evidence for a periodic train of particle bursts occurring with a 7.7‐s period from 40 to 130 s after the release. A transient electric field pulse of 200 mV/m appeared just before the particle flux increase started. Electrostatic wave emissions around 2 kHz, as well as a delayed perturbation of the E region below the plasma cloud were also observed. Some of the particle observations are interpreted in terms of field‐aligned electrostatic acceleration a few hundred kilometers above the injected plasma cloud. It is suggested that the accelerating electric field was created by an instability driven by field‐aligned currents caused by the plasma cloud release. This paper gives an overview of the experiment design and the general result. Particular observations and their interpretation are discussed in more detail in companion papers.

Correlated whistler and electron plasma oscillation bursts detected on ISEE‐3

The ISEE‐3 plasma wave instrument detects associated bursts of electron plasma oscillations and whistler mode waves at an average rate of event one every two days. The plasma wave measurements give the electron number density, and simultaneously measured E and B amplitudes are used to deduce an index of refraction consistent with whistler mode propagation for the measured number density and magnetic field. Burst durations are a few minutes, with some trains of bursts lasting up to an hour. Individual spectral scans (two per second) reveal that the whistler and plasma wave amplitude‐time profiles differ within a burst. Peak plasma wave amplitudes are near one mV/m, and the peak whistler mode energy density exceeds that of the plasma oscillations by about a factor 100. The frequency of the whistler mode wave observed in one well diagnosed event agrees with the predictions of the heat flux whistler instability theory. The associated plasma wave instability probably requires a bump‐on‐tail feature in the heat flux electron component, possibly due to impulsive heating elsewhere on the field‐line connecting to ISEE 3.

The Acoustic Reflex Pattern Studied by the Averaging Technique

The acoustic reflex threshold and its pattern in response to stimuli of different intensities, were investigated by means of the signal-averaging technique in 20 normal, 20 sensorineural-impaired and 10 successfully stapedectomized ears. Trains of tone bursts between 110 and 0 dB HL were used. The frequencies tested were 500, 1 000, 2 000 and 4 000 Hz. In all normal subjects, the pattern of the acoustic reflex for stimuli between 110 and 100 dB HL was biphasic with an initial positive plateau followed by a longer negative one. For stimuli below 80 dB HL, the pattern of the reflex was monophasic with a single positive peak. In the sensorineural-impaired ears, the same double pattern of the waveform was obtained. In the stapedectomized ears, no compliance changes were observed for any sound stimuli. By the averaging technique, the difference between the acoustic reflex threshold and the auditory threshold was found to be between 7.5 and 32.5 dB, in normal and sensorineural-impaired ears.

A new mode of X-ray bursts from MXB1730–335

We report here on the unusual behaviour of MXB1730–335, the rapid burster1 as observed by the X-ray astronomy satellite Hakucho between 8 and 22 August 19792. MXB1730–335 is a unique burst source which generates rapidly repetitive bursts lasting between a few and tens of seconds. In the present observations, however, its behaviour was very different to that previously observed, in that the bursts of a trapezoidal profile were dominant. The profile is characterised by a flat top lasting between 30s and 10 min. A long train of such trapezoidal bursts was seen for the first time and clearly revealed a new mode of the rapid burster.

Synergism and antagonism of neurons caused by an electrical synapse

To investigate the role of electrical junctions in the nervous system, a model system consisting of two nearly identical neurons electrotonically coupled is studied. We assume that each neuron discharges a train of impulses or bursts either spontaneously or under constant stimulus via chemical synapses. It is known that not only an electric current but also chemical substances whose molecular weight is about 1000 can pass through the junction of an electrical synapse (gap junction). So, our model system is regarded as a set of non-linear oscillators coupled by diffusion, and it may be described by a system of ordinary differential equations. Neurons are excited constantly when they are stimulated by an electric current above the threshold level. Therefore, we expect Hopf bifurcation to occur at the critical magnitude of a stimulating electric current in the system of differential equations which describes the dynamics of a single neuron. Studying our model system according to the theory of Hopf bifurcation, we found regions of diffusion constants of the electrical junction which give two kinds of periodic solutions. One is the solution where two neurons oscillate in phase synchrony. The other is where two neurons oscillate 180° out of phase. In the case where one neuron is described by the BVP model, the following was found by computer simulation. When the initial difference between the phase of two neurons is small, the two neurons come to oscillate synchronously. If the initial difference is large, however, the two come to be excited alternately. The physiological implications of these results are discussed.

Average‐rate, fundamental and harmonic‐distortion components of responses of cochlear nerve fibers to single‐frequency tone bursts: Comparison with an exponential model

The effects of stimulus envelope on the response characteristics of cochlear nerve fibers can be studied with a class of stimuli of the form p(t) = ex(t) sin (ωt). In this study, the modulating function eg(t) was chosen to produce a train of tone bursts of specified duty cycle and rise/fall times. The technique of Fourier analysis of period histograms described by Kim et al. (preceding abstract) has been extended to handle variations in response components R0,R1, and θ1 as a function of time both within and between each tone burst in a train of bursts. Using tone bursts of 320 ms duration and 20 ms rise/fall times with a duty cycle of 21% we have observed that, during the course of a tone burst: (1) both R0 and R1 rapidly reach a peak value and then decline over the following 50–100 ms to quasi‐steady—state values; (2) the time courses of R0 and R1 during a tone burst are almost identical in shape, i.e., the ratio, R1/R0, reaches its maximum value rapidly and remains constant throughout the duration of a tone burst despite noticeable fluctuations in R1 and R0; (3) the fundamental phase θ1, is constant throughout the total duration of a tone burst; (4) R1R0 saturates at lower sound pressure levels (SPL) than either R0 or R1; (5) the shapes of R0 and R1 vs SPL curves change substantially and progressively for successive periods during the onset portion of the response; and (6) in some cases, the R0 and R1 versus SPL curves for individual periods during the first 12–20 ms following tone burst onset show pronounced nonmonotonic behavior with maxima occurring at as low as 50 dB re 20 μN/m2.