Showing papers on "Latency (engineering) published in 1978"

Initial discharge latency and threshold considerations for some neurons in cochlear nuclear complex of the cat.

Abstract: 1. Latency behavior of neurons in the cochlear nuclear complex was studied in 45 barbiturate-anesthetized cats. Stimuli were tonal bursts usually 50-500 ms in duration. 2. Latency of the initial discharge is a systematic function of the frequency and intensity of the tone for a large class of neurons which are termed latency precedence cells. Most cells in the anteroventral cochlear nucleus and many neurons in the anterior division of the posteroventral nucleus belong to this class. Unless otherwise stated, all findings pertain to this cell group. 3. There is usually a correspondence between the discharge rate of a given neuron and the latency of the initial discharge, the higher the discharge rate the shorter the latency. Hence, for any intensity level evoking less than saturation discharge rate, initial discharge latency tends to be ‘shortest for best-frequency stimuli and lengthens systematically as the stimulating frequency departs in either direction from best frequency. However, for some cells, intense stimuli above best frequency evoke initial discharges at latencies which are similar to those produced by best-frequency stimuli. 4. An unexpected finding was that the initial discharge at threshold is a low probability event that can be evoked, except for a short initial time period, by any stimulus cycle throughout the tone duration. Hence, tone duration is a parameter in determining the threshold. Within limits, the longer the

Latency variability and the identification of antidromically activated neurons in mammalian brain

Abstract: While collision techniques (see, e.g., Bishop et al., 1962; Fuller and Schlag, 1976; Swadlow, 1974a) are generally regarded as most appropriate for the extracellular identification of antidromic activation, they cannot always be applied to each unit encountered. In such cases, latency variability of 0.1 msec is often chosen as a maximum which, outside of the relative refractory period, is compatible with antidromic activation. Using this criterion, neurons with a latency variability of more than 0.1 msec are either rejected from analysis or considered to be synaptically activated. Activity-dependent variations in axonal conduction velocity have, however, been observed in a number of regions within both the peripheral and central nervous system. In both myelinated and non-myelinated callosal axons of the rabbit for example (Swadlow, 1974b; Swadlow and Waxman, 1975; Swadlow and Waxman, 1976; Waxman and Swadlow, 1976) and in callosal axons of the macaque monkey (in preparation), the relative refractory period is followed by a supernormal period of increased conduction velocity and decreased threshold and a subsequent subnormal period of decreased conduction velocity and increased threshold. These effects are of a sufficient magnitude and duration to produce significant variability in antidromic latency when stimuli are presented without regard to prior (spontaneous) impulse activity. In the present note we describe this antidromic latency variability, a method for essentially eliminating this variability, and the usefulness of these phenomena in the identification of antidromically activated neurons.

Variation in latency times of visually evoked cortical potentials.

Abstract: Latency times of visually evoked cortical potentials stimulated by reversal of a slow checkerboard pattern are highly dependent on the time needed to accomplish the reversal movement. If, owing to the method, the pattern reversal time is not kept stable, variability of the latency times is unnecessarily high for clinical purposes. This may be the case when television equipment is used.

Evidence for a correlation between the latency of an early component of auditory evoked potentials and the brain levels of serotonin in albino rats.

Abstract: Changes in brain serotonin levels are correlated with the latency of an early component of auditory evoked potentials (EAEP) in rats. In fact 5-hidroxytryptophan provokes an increase both in serotonin brain synthesis and in the latency of EAEP. On the other hand, PCPA provokes an opposite effect.

Two linear rules relate the latencies of visual responses to their critical durations.

Abstract: The latency of a neural response sets a limit on its critical duration since stimulation delivered after a response has already occurred can no longer affect that response. However, this tautologic upper limit does not uniquely define the critical duration. Intracellular recordings from the lateral eye of Limulus yield two linear rules which empirically relate the critical duration of a neural response to its latency: When response magnitude (peak amplitude, spike frequency) is used to construct the temporal summation function, the critical duration is equal to the latency minus a constant. When response latency is used instead, the critical duration of the response latency is equal to the latency divided by a constant.

Latency to respond and conjugate lateral eye movements: a methodological and theoretical note.

Abstract: The relationship between latency to first response and lateral eye movements was investigated for 52 preschool and primary grade children. Latency to respond correlated significantly with number of eye movements observed for each child. Significantly greater latency occurred for spatial questions than for verbal reasoning questions. Methodological and theoretical implications of latency to first response in relation to the study of conjugate lateral eye movements are briefly described.

A method for averaging response latency patterns of antidromically excited neurons.

Abstract: Electrical stimulation of the axon evokes an action potential which travels antidromically (backwards) up the cell body, where it can be recorded with a microelectrode. Since the antidromic invasion implies no synaptic transmission between the stimulation and recording sites, its recording is frequently used in neurophysiology to identify axonal projections of different neurons (e.g., 4,5). The extracellular recording of antidromic invasion of the cell body can provide, besides anatomical information , data about synaptic inputs impinging on the neuron. Examining respiratory neurons, Merrill (5) demonstrated that the temporal pattern of their antidromic invasion latencies correlates with the polarization of the soma. When the axon was stimulated with a constant frequency, the antidromic latency (AL) measured to the somato-dendritic (SD) spike varied regularly with respiratory cycle (to 0.5 ms) and was found shorter during the period of synaptic excitation of the neuron. Merrill's recording technique was based on a dot display of antidromic responses. The technique of direct recording of AL variations has been also used for estimation of the excitability changes in other neurons, namely preganglionic sympathetic neurons (3) or spinal motoneurons (2). In this

Cognitive Style and Visual Analysis in First Graders of High and Low Verbal Ability

Abstract: Summary-100 first graders were screened for verbal ability and sub divided into high and low quarriles with 25 children in each group Field independence, visual analysis, and spatial visualization of these groups was investigated and their social communication skills were assessed Since small age differences were observed on a number of the tasks, age was controlled as a covariate As predicted, those of high verbal ability modified response latency under task uncertainty, performed better in spatial analysis, and showed greater social resourcefulness They were more accurate in discrimination of similarities but did not differ from those of low verbal ability in accuracy on the Children's Embedded Figures test or in discrimination of differences Intertask relationships and the influence of sex and age on performance were discussed Currently there is disagreement about the relative usefulness of accuracy and latency measures of cognitive style Children are consistent over time in their latencies, which tend to lengthen with age (Kagan & Kogan, 1970) Latency may not be as important in the application of children's problem-solving skills as accuracy Block, Block, and Harrington (1974) reported preschool children's latency on the Matching Familiar Figures test predicted few differences in personality and behavior Accuracy scores in perceptual matching were related to many important differences Kogan (1976) in a recent review noted that though classification and scoring on both latency and accuracy was a promising research strategy, latency was a more reliable index of individual differences In support of this view, Rollins and Genser (1977) reported that latency on Matching Familiar Figures but not accuracy was related to performance on a concept-attainment task In their extensive study of differences among children, Zelniker and Jeffrey (1976) found that latency measures were stable over two versions of Matching Familiar Figures However, errors on this test depended on specific demands of the modified task, attention to detail or global analysis Latency measures are more internally consistent than accuracy in matching figures (Zelniker, Bentler, & Renan, 1977) The moderate negative correlations between accuracy and latency produce problems for analysis because errors are unreliable (Ault, Mitchell, & Hartmann, 1976) The relationship between accurate visual analysis and latency may change

Minimizing Latency in CCD Memories

Abstract: Serial memories built from charge-coupled devices (CCD's) offer an opportunity for minimizing latency times not available with the more conventional drum and disk (serial) memory units. Let r be the ratio of the maximum to the minimum clocking rates for the CCD memory. We show that in many practical situations the average latency can be reduced from 1/2 to 1/(1 + √r) of a revolution time if the optimal clocking strategy is used when the CCD is idle.

Data transfer controller

Abstract: PURPOSE:To shorten a latency time caused by the confliction among memory access operations from a plural number of cahnnels to the same bank, by providing memory buffer registers MBR, conventionally common-used by a plural number of channels, corresponding to channels.

An efficient algorithm for allocating paged, drum-like storage

Abstract: Cody and Coffman have studied the problem of distributing a set of a equal-size records among the sectors of a drum-like storage device so as to minimize the average rotational latency cost. This paper is an extension of that work. We employ the same model but a different latency delay function. Motivated by the NP-completeness of the general problem and the fact that an arbitrary assignment can have an expected latency cost almost twice that of an optimal assignment, we propose and analyze a fast heuristic whose performance compares favorably with that of an optimal algorithm.

Multiple observations and latency functions: A further note on response latency in signal detection

Abstract: S. Koppell (see record 1976-29070-001) claims that R. Pike's (see record 1973-20129-001) multiple-observations model for signal detection can be conceived as giving rise to a "latency function," whereby the latency of response decreases with distance of the median position of the observations from the criterion point. It is demonstrated that while this claim is correct, the form of the latency function generated by the model is different in important respects from that usually described by the more general latency-function hypothesis-in particular, it is a dual-valued function-and this difference in form is important in terms of predictions of the multiple-observations model as compared with predictions to be made of the general latency-function hypothesis. The form of the function is derived by means of a consideration of order statistics and is shown to be quite general. The possibility of considering the mean of the sample of observations as generating a latency function is discussed, and the relationship between the mean or median to confidence judgments is considered. (PsycINFO Database Record (c) 2006 APA, all rights reserved).