Decreasing Interstimulus Interval Research Articles

The effects of call-like masking diminish after nightly exposure to conspecific choruses in green treefrogs (Hyla cinerea).

One of the major difficulties encountered by animals that select mates using acoustic signals is discriminating individual calls from the background noise generated by other conspecifics. Reducing the effects of conspecific masking could improve discrimination of individual calls from background noise. We used auditory evoked potentials to investigate the effects of forward masking on the responses to artificial calls in male and female treefrogs (Hyla cinerea), as well as whether hearing advertisement calls over several nights, as happens in natural frog choruses, could modify the effects of masking. We found that response amplitude decreased with decreasing interstimulus interval when the masker was equal in amplitude to the stimulus. We also found evidence of a priming effect, whereby response amplitude at lower masker amplitudes was greater than when the target stimulus was not preceded by a masker. Finally, we found that the effect of masking was diminished by 10 nights of chorus exposure (i.e. responses were stronger to target stimuli), whereas there was no change in response in the control group. Our results show that hearing dynamic social stimuli, such as frog choruses, can alter the responses of the auditory periphery in a way that could enhance the detection of and response to conspecific acoustic communication signals.

Temporal Resolution of Auditory Perception in Relation to Perception, Memory, and Language Skills in Typical Children

This study examined temporal resolution of auditory perception (TRAP) in relation to speech perception and phonological working memory in one experiment and in relation to measures of rapid naming, understanding of grammatical contrasts, and phonological awareness in a second experiment. In the TRAP test, 6- to 9-year-old children discriminated four pairs of two sine tones, 878 Hz and 1350 Hz, presented in blocks with stepwise decreasing interstimulus intervals from 256 ms to 8 ms. In Experiment 1, weak but significant correlations between TRAP and speech perception and phonological working memory were found, as well as a significantly lower TRAP performance by girls. Experiment 2 indicated a significant relation between TRAP and the phonological awareness task. The results give qualified support to the notion of a weak relationship between TRAP and speech perception and language skills among typical children. However, the gender differences in TRAP performance, the limited variance explained by the regression models, and the finding that only one of the language parameters correlated with TRAP do not support the notion of a causal relationship between language skills and TRAP. The possibility that TRAP is connected to general neurological maturation rather than specifically to language abilities is discussed.

Isoflurane plus nitrous oxide versus propofol for recording of motor evoked potentials after high frequency repetitive electrical stimulation

The goal of this study was to test the influence of two widespread techniques of general anesthesia on motor evoked potentials (MEP) in response to transcranial and direct cortical high frequency repetitive electrical stimulation. Total intravenous anesthesia (TIVA) based on propofol and alfentanil was examined in 17 patients (group A), and balanced anesthesia (BA), based on nitrous oxide, isoflurane and fentanyl, was studied in 13 patients (group B). Distinct motor responses were available in 15 of 17 patients (88%) of group A, and in one of 13 patients (8%) of group B. Amplitudes increased significantly with increasing stimulus intensity and number of pulses under conditions of TIVA. At the same time, latencies decreased significantly with increasing stimulus intensity and decreasing interstimulus interval, but not with increasing number of pulses. It is hypothesized that propofol suppresses corticospinal I-waves at the cortical level, resulting in a conduction block at the level of the α-motoneuron, and that this effect may be overcome by high frequency repetitive stimulation. In contrast, nitrous oxide and isoflurane seem to have an additional suppressive effect on corticospinal D-waves, which may be overcome by higher stimulation intensity. In conclusion, transcranial high frequency repetitive stimulation and TIVA provide a feasible setting for intraoperative MEP monitoring, while higher doses of nitrous oxide and isoflurane are not compatible with recording of muscular activity elicited by the stimulation technique as described.

A comparison of the repetitive click and conditioning-testing P50 paradigms

The auditory P50 ERP component has previously been studied either in the repetitive click or the conditioning-testing (C-T) paradigm. For 20 subjects, we compared 4 repetitive click and 4 C-T protocols in a single experimental session with identical recording techniques and with interclick intervals comparable to the C-T intervals. In the C-T protocols, a long interval between click pairs ensured full recovery of P50 to the C click. The analysis of P50 topographies provided strong evidence that the same component was measured in the two paradigms. For both paradigms, P50 amplitude was progressively suppressed as the interclick or C-T interval decreased ( P<0.0001), with parallel interval vs. P50 amplitude regression lines for the two paradigms. There was a strong trend ( P=0.08) for the repetitive click amplitudes to be smaller than T amplitudes for comparable repetitive click and C-T intervals. Equivalently, this strong trend suggests that repetitive click intervals must be longer (by about 300 ms) than the C-T interval to generate equivalent amplitude P50 responses. We conclude that the same component is measured in both paradigms, that P50 amplitude decreases with decreasing interstimulus intervals in both paradigms, and that in normals, for comparable inter-click and C-T intervals, there is greater P50 suppression in the repetitive click paradigm. Finally, we note that the comparison of paradigms within normals does not necessarily apply to clinical samples.

Auditory Steady-State Responses in the Rabbit

The authors have studied auditory brainstem (ABRs), middle latency (MLRs) and steady-state potentials (SSRs) in 15 adult male rabbits weighing between 2.5 and 3 kg in order to verify if SSRs are due to a mere superimposition of ABRs and MLRs or to a resonance phenomenon. Ten of them were awake while 5 were studied under urethane anesthesia. Acoustic stimuli consisted in 0.1-ms square-wave pulses delivered at presentation rates ranging between 1 and 80/s at a stimulus intensity of 80 dB p.e. SPL. Our data show that reliable auditory SSRs can be obtained in the rabbit at a presentation rate of 30 stimuli/s, probably due to the superimposition of ABRs and MLR Pb waves which show an interwave interval of about 35 ms. The nonlinear aspects which can be detected are probably due to the effect of decreasing interstimulus intervals on the duration and amplitude of the Pb wave. It can then be concluded that SSRs in the rabbit are due more to a superimposition of ABR and MLR waves than to a resonance phenomenon.

Resting, and rate-dependent depression of Vmax of guinea-pig ventricular action potentials by amiodarone and desethylamiodarone.

1 The cellular electrophysiological effects of amiodarone and its metabolite desethylamiodarone (DEA) were studied in guinea-pig ventricular myocardium by use of standard microelectrode techniques. 2 Both compounds produced significant increases in action potential duration (Class III antiarrhythmic effect) and decreases in maximum rate of depolarization (Class I effect), at clinically relevant concentrations. 3 The Class I effects were rate-dependent, with small (0-16%) falls in maximum depolarization rate in the absence of stimulation ('resting block') and progressively larger effects at decreasing interstimulus intervals (range 1200-300 ms). 4 The kinetics of onset and offset of the Class I effect in response to a step change in driving rate were quite fast for both drugs (comparable to those reported for Class Ib agents). 5 It is concluded that this unique combination of Class III action plus Class I effects with fast onset and offset kinetics may help explain the great efficacy of amiodarone in antiarrhythmic therapy.

刺激音の持続時間とＡＢＲ

Auditory brainstem response elicited by tone bursts were recorded from the scalp of human subjects. Response alternations produced by changes in the duration time were evaluated.The latency and the amplitude of wave V and VI were increased with increase of tone bursts duration, whereas latencies of wave I to III (and IV) were less increased, and the amplitude of them tended to decrease. These changes were not caused by the decreasing interstimulus interval, but by the increasing stimulus duration.Although, there was no distinct explanation for the changes of ABR recording of slow component had suggest that the changes in the slow component may play an important roll.

Modelling compound action potentials of peripheral nerves in situ. III. Nerve propagation in the refractory period

Compound nerve action potentials (CAPs) of sural nerves of healthy persons were measured in the relative refractory period of the fibres. Double stimuli were used with interstimulus intervals ranging from 0.7 to 4.0 msec. The CAP latency increase, its amplitude decrease and its wave shape alterations with decreasing interstimulus interval are discussed, using a model description. Recovery functions for the single fibre action potential in the relative refractory period are defined. These recovery functions, however, cannot sufficiently explain the CAP amplitude diminutions actually measured. Apparently in the relative refractory period an increasing number of fibres ceases to propagate an action potential when the stimulus interval is shortened. This effect, which is caused by subthreshold stimulation, predominantly involves the slower fibres. The usual derivation of refractory period parameters in clinical practice is reviewed.

Effects of Interstimulus Interval on Latency of the Brainstem Auditory Evoked Potential

Peak latency of the inferior collicular response (wave V) of the brainstem auditory evoked potential (BAEP) increases with decreasing interstimulus interval (ISI). The present research investigated relative peak shifts of major components of the BAEP in an attempt to identify the source of the observed shift in wave V. Peripheral as well as central transmission times (CTT) were computed for 9 young adults between an ISI of 100 msec and an ISI of 10 msec. The results indicate that shifts in wave V latency with changing ISI are due to a combination of central and peripheral processes. The magnitude of the shift observed for wave V was approximately 0.50 msec. This increase in latency was accounted for by an average 0.29 msec increase in peripheral transmission time, a 0.14 msec increase in CTT between waves I and III, and a 0.07 msec increase in CTT between waves III and V. The results suggest a dual process underlying latency changes in wave V of the BAEP as a function of decreasing ISI. These are peripheral adaptation or fatigue and central processes that may include short-term habituation.

The Psychological Refractory Period and the Effect of Stimulus Discriminability

The 'psychological refractory period' has come to be the accepted label for response-delay phenomena in a double-stimulation situation. In the classic arrangement the two stimuli S1 and S2, requiring the two responses R1 and R2, are presented at interstimulus intervals of less than 500 msec. With decreasing interstimulus intervals the latency of R2 is known to increase steadily. The early studies on the refractory period were primarily concerned with the probability aspects of the various parameters involved. These parametric studies have produced a wealth of results that can hardly be encompassed by any one theory. Among the various theories that have been proposed over the years, three are most likely to survive: singlechannel, expectancy, and response-conflict theory. Single-channel theory, first proposed by Craik (1948), explains the delay in R2 in terms of a limited capacity of the central processing system (single-channel). The single channel can process only one stimulus at a time. Under double or sequential stimulation, signals are either queued or lost if the pace of their temporal presentation exceeds the basic processing time of the channel. According to this assumption, a delay in R2 should occur if the interstimulus interval falls below a critical value. In contrast to the single-channel notion, Poulton (1950) attributed delays in R2 at short interstimulus intervals to the fact that the subject

Some experiments on refractoriness

When two stimuli are presented in rapid succession and a subject has either to react to both or to the second stimulus only, the second reaction time increases with decreasing interstimulus interval. Several theories have been put forward to explain this phenomenon. Experiments are described with which the expectancy theory and the intermittency theory can be tested. From the experimental data it is argued that the effect of expectancy is to be neglected with interstimulus intervals shorter than .6 of a second. There appeared to be a clear discrepancy between the predicted data based on an internittency hypothesis and the experimental data.