Showing papers on "Latency (engineering) published in 1988"

Latency of auditory brain-stem responses and otoacoustic emissions using tone-burst stimuli

Abstract: A comparison of the latency of auditory brain-stem responses (ABR) and evoked otoacoustic emissions (EOAE) has led to an interpretation for the travel of transients in the peripheral auditory system that is consistent with both sets of data. The "cochlear echo" theory for the origin of the EOAE indicates that the latency of a particular frequency component back to the ear canal should be twice the forward latency of its characteristic place in the cochlea. The latency of wave V of the ABR to tone-burst stimuli can be described as the sum of two components: (1) a component that varies with intensity and frequency in an orderly and predictable manner and (2) a component that is independent of both intensity and frequency. Because the EOAE data can be predicted by taking twice the value of component (1) of the ABR latency, this component is interpreted to be due to mechanical travel through the cochlea. A consequence of this interpretation is that the remaining neural component of the ABR latency must be relatively independent of frequency and intensity.

Novel approaches to the problem of latency jitter.

Abstract: This paper deals with the issue of variable latencies of single potentials. A new method is proposed for obtaining estimates of single latency shifts, which allows furthermore a statistical test on the presence of latency jitter. In the Appendix, we give a precise description of the algorithmic procedure in order to allow an implementation of the new approach. A simulation study using real data from 41 children demonstrated that the procedure performed much better than the familiar Woody algorithm which produced highly unstable estimates. The new statistical test on presence of latency jitter was validated and also evaluated using simulations. The test was specifically sensitive to latency jitter but not to other types of variation of single potentials. In an application of real flashevoked potentials evidence for the presence of variable latencies was found.

Propofol infusion and auditory evoked potentials

Abstract: The effects of propofol on auditory evoked potentials (brainstem and middle latency responses) were recorded in six patients. Two different infusion rates were used, 54 and 108 micrograms/kg/minute. Effects on brainstem responses were not found. Regression of amplitude and latency of middle latency auditory potentials were dose related (p less than 0.01).

A pharmacological distinction between the long and short latency pathways of the human blink reflex revealed with tobacco.

Abstract: In three, normal, human subjects, tobacco smoking was used as a pharmacological probe to modify differentially the direct and indirect pathways underlying the blink reflex. The latency of the indirect R2 component of the orbicularis oculis electromyogram evoked by electrical stimulation of the trigeminal supraorbital nerve transiently increased 20-80% after smoking, while the latency of the shorter latency, direct R1 component remained constant. The magnitude of both components of the blink reflex transiently decreased. The data demonstrate that tobacco smoking can differentially alter the long and short latency components of the blink reflex, and suggest that these effects result from modifications of central pathways sensitive to nicotine.

Saccadic latency as a measure of afferent visual conduction.

Abstract: Latency to initiate a saccadic eye movement to a visual target, and visual evoked potential, were measured in seven patients with resolved unilateral optic neuritis. Saccades were delayed when the target was presented to the clinically involved eye, but were normal when the contralateral eye was tested. With binocular target presentation, saccades were symmetric between eyes and normal in latency. In two patients with pituitary adenoma and low-grade bitemporal field defects, saccades were delayed when targets were presented in the temporal field, but were within normal limits when presented in the nasal field. These results cannot be attributed to lesions in the motor pathways. It is concluded that saccadic latency to visual targets is a valid measure of afferent conduction. If the robust delays found in this study prove to have test-retest reliability, saccadic latency may provide a measure of afferent function which is sensitive to the demyelination that preceeds neuronal degeneration and sensitivity loss in patients suspected of having optic neuropathy.

Changes in the auditory middle latency responses during all-night sleep recording.

Abstract: The middle latency response (MLR) using wide band-pass filters shows marked changes in amplitude, latency and configuration in sleep. The components with latencies greater than 20 ms show the greatest variability. There is a significant increase in Pa latency in stages 2 and stages 3/4, and in some cases a disappearance of the Nb component with the development of a broad positivity of latency intermediate to Pa and Pb which dominates the response. The responses in REM are of similar latency and configuration as in wakefulness but of reduced amplitude. The 40 Hz response is markedly reduced in amplitude in all sleep stages reflecting a decrease in the contribution of the middle latency components to this composite response. This appears to arise through a loss of 40 Hz periodicity in slow wave sleep and an increase in the slow 10 Hz component. In REM sleep, there is an overall reduction in amplitude. Much of the reported variability of the MLR in the literature arises from the widely differing band-pass fi...

Experimental determination of latency, severity, and outcome in CNS decompression sickness.

Abstract: Twenty-eight dogs underwent a 300 fsw chamber dive designed to generate spinal cord decompression sickness (DCS), which was detected by observing a reduction in the amplitude of the spinal somatosensory evoked potential (SEP). After an interval of 15 min on the surface following diagnosis, the animals received a therapeutic recompression. The latency was defined as the time between surfacing from the dive and the diagnosis of DCS, the severity as the minimum SEP amplitude, and the outcome as the amplitude of the SEP after 2 h of treatment. Significant correlations between latency and severity (P less than 0.05), latency and outcome (P less than 0.01), and severity and outcome (P less than 0.05) were found. Canine spinal cord latency is shown to be very similar to that found in man up to a surface interval of 30 min. The association between latency, severity, and outcome of spinal cord DCS is discussed with reference to the possible mechanisms involved in this disease.

Latency of the pupillary response

Abstract: The authors give an explanation of pupillary latency in terms of nonminimum phase lag. Minimum phase lag is that phase associated with a simple linear lag element; nonminimum phase is associated with a true delay element modeled as exp (-ST). Latency can be accurately modeled by a delay element. The authors experimentally demonstrate that pupillary latency increases with reductions in intensity and increases with frequency of the square-wave stimuli. They summarize these characteristics with a model. >

Error detection with latency in sequential circuits

Abstract: An approach is proposed to encoding states of sequential circuits that takes advantage of the concept of error detection with latency, and which is applicable to a much broader class of sequential machines. An encoding methodology is introduced that uses tree codes for online detection of sequencing errors with latency in sequential circuits. This approach has the potential to yield designs with less complexity and greater error coverage than schemes based on block codes. The potential benefits this approach are demonstrated, including increased error coverage with simultaneous reductions in circuit complexity. >

Absence tasks of the set-size effect in memory-search in the absence of a preprobe delay

Abstract: In the traditional Sternberg (1966) paradigm, response latency increases linearly with increases in the size of the positive set (the set-size effect). The results of four experiments converge on the conclusion that this set-size effect depends on a delay before the presentation of the memory probe. In Experiment 1, subjects were required to respond as soon as a repetition occurred in a series of digits. Despite the similarity of this task to memory-search tasks that invariably show set-size effects, there was no increase in response latency with increasing series length. Neither the inclusion of negative trials (Experiment 2) nor the explicit designation of the test digit (Experiment 3) resulted in the typical set-size effect. However, the introduction of a 1-sec preprobe delay (Experiment 4) resulted in a set-size effect of 31 msec/item.

Visual evoked responses in hereditary motor and sensory neuropathies.

Abstract: — The P2 latency of the pattern reversal visual evoked response was measured in 11 patients with heriditary motor and sensory neuropathy (HMSN). The P2 latency was inversely related to the peripheral nerve conduction velocity, but no significant relation was found between the P2 latency and the age of the patients or the duration of their symptoms. When the whole group was considered the mean P2 latency was longer but not significantly different from a control group. When the 11 patients were differentiated into HMSN 1 (5 males) and HMSN II (2 females, 4 males) the P2 latencies of the patients with HMSN I were significantly longer than those with HMSN II. The data support earlier findings that subclinical involvement of the optic nerve may occur in HMSN and suggest that measurement of P2 latency may be of value in the differentiation of HMSN. More than two subtypes, however, may exist.

A new technique for interpreting the BAER in cochlear disease.

Abstract: We found, by studying 20 normal ears and 34 ears with cochlear disease, that the brainstem auditory evoked response (BAER) wave I latency was a good predictor of the I-V interval (r = -0.67, p less than 0.001), whereas hearing loss had little predictive value. The normal and hearing-loss groups generated regression lines (wave I latency vs I-V latency) that did not differ significantly from each other. A normal range of I-V intervals can be established for any wave I latency, increasing the sensitivity of the BAER.

Performance evaluation of a token ring network with dual latency stations

Abstract: The authors present a method for performance improvement of token ring networks that is based on the use of stations with two latency states. A station is able to enter a lower latency state whenever its message queue is empty. They present a detailed evaluation and comparison of network performance, based on both analytical and simulation results. The performance of a dual latency token ring is analyzed for the case of limited-to-one service, symmetric traffic, and is compared to the performance of a conventional token ring operating with limited-to-one, gated, or exhaustive service. The authors use discrete-event simulation to model the behavior and performance of a duel latency ring with asymmetric traffic, and compare with the above three service disciplines. Results show a significant reduction in mean waiting time for the dual latency ring, with performance approaching or exceeding that of gated and exhaustive service, for certain ranges of network utilization. >

The difference in the tail-flick but not hot-plate response latency between C57BL/6 and DBA/2J mice.

Abstract: The tail-flick latency, measured using radiant heat as a noxious stimulus, was significantly shorter in C57BL/6 than in DBA/2J mice, while no significant interstrain differences were observed in the hot-plate test. The experiments in which the animals' tail was painted indicated that the difference in the tail-flick latency between strains was caused by the difference in the color of animal's coat.

A dormant subcircuit model for maximizing iteration latency

Abstract: An approach for modeling dormant subcircuits is presented that utilizes iteration latency to provide speed improvements that are comparable to the potential speed improvements of an independent time step approach. This scheme minimizes the work required on the first iteration at a time point, which is the normal limiting factor in iteration latency schemes. However, since simulations are performed for each subcircuit at each time point, the penalty for backing up when truncation error is unacceptable is minimized. >

The difference in the tail-flick latency between C57BL/6 and DBA/2J mice.

Abstract: The tail-flick latency, measured using radiant heat as a noxious stimulus, was significantly shorter in C57BL/6 than in DBA/2J mice, while no significant interstrain differences were observed in the hot-plate test. The experiments in which the animals' tail was painted indicated that the difference in the tail-flick latency between strains was caused by the difference in the color of animal's coat.