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PubMed1992

Xenopus exhibits seasonal variation in retinotectal latency but not tecto-isthmo-tectal latency.

1. The tectum of Xenopus receives visuotopic input from both eyes. The contralateral eye's projection reaches the tectum directly, via the optic nerve. The ipsilateral eye's projection reaches the tectum indirectly, via the nucleus isthmi and isthmo-tectal projection. 2. Because of the multi-synaptic nature of the ipsilateral pathway, there is an inherent delay between the time that information from the contralateral eye reaches the tectum and the time that information from the ipsilateral eye arrives at the tectum. The length of the intertectal delay is a function of the latencies of the contralateral and ipsilateral pathways. 3. The length of this intertectal delay has functional, as well as developmental, implications with regard to the role of N-methyl-D-aspartate receptors in tectal cell activity and development of orderly synaptic connections. 4. We have found that the latencies of the contralateral and ipsilateral pathways exhibit a seasonal variation, increasing during the winter months. The increases of both latencies during the winter were of similar magnitude, indicating that there were no significant changes in intertectal delay. The seasonal alteration in contralateral latency was not affected by dark-rearing and was affected to only a minor extent by a week-long alteration of ambient temperature.

Animals↗

PubMed1988

H reflex latency as an adequate predictor of the spinal evoked potential latency.

By stimulation of the posterior tibial nerve, somatosensory responses can be recorded at the level of the popliteal fossa, thoraco-lumbar spinal region and scalp. The thoraco-lumbar spinal potential is frequently difficult to record. Therefore several methods to estimate its latency were used and the results were compared with the real latency of the N24 recorded at spinal level in a group of healthy volunteers. A formula using the Hoffmann reflex latency (H-M interval) proved to be the most adequate for this purpose. By knowing the spinal potential latency, either through direct recording or through estimation by the formula, determination of a central conduction time, the N24-P40 interval, is possible. Normative values for this parameter are given.

Adult↗

PubMed1989

Behavioral and neural characteristics of short-latency and long-latency conditioned responses in cats.

Head movements to the conditioned stimulus (a tone CS to the left ear) were studied in 6 cats. An attempt was made to differentiate an orienting, short-latency (alpha) response from the long-latency conditioned (delayed) response. The unconditioned stimulus (UCS) was a brain stimulation to the lateral hypothalamus eliciting, in addition to orienting and approach behavior, a specific, stereotypical head movement. These behavioral characteristics of the unconditioned head movement were used for differentiating it from the conditioned short-latency head movement. Paired conditioning and randomly unpaired control sessions (5 daily sessions each) were given in balanced order to each animal. Evoked neural responses in the hippocampus and cingulate cortex were recorded simultaneously to compare the time-amplitude characteristics of evoked responses to earlier findings in multiple-unit recordings. The results supported the differentiation of the behavioral responses. The time-amplitude course of the evoked neural responses showed complex changes, appearing as an increase in the negativity during the alpha-response period (150- to 450-ms interstimulus interval [ISI]) and as an increase in the positivity during the long-latency period (700- to 1,000-ms ISI + 150- to 450-ms UCS period) on omitted-UCS (CS-alone test) trials.

Alpha Rhythm↗

PubMed1993

Response latency, latency-based receiver-operating characteristics, and uncertainty about interaural phase in the detection of in-phase and out-of-phase tones presented in noise.

Subjects were given the task of detecting tonal signals presented in a continuous background of white noise which was always in phase at the ears (No). The signals were either in phase (So), or phase-reversed (S pi) at the ears. The analysis of response latencies (for similar levels of performance) indicated that there were consistent differences in the processing of the two types of signals. Latencies were longer, and somewhat more variable, for S pi than for So signals. It was also found that the theory of signal detectability can contribute to an understanding of what and how decisions are made. Latencies were treated as confidence ratings in order to determine latency-based receiver operating characteristics (LROCs) for the detection task. It was observed that the LROCs for the interaural condition No-So tend to leave the origin at a steeper angle than do those for the interaural condition No-S pi, presumably reflecting the different sensory and decision processes employed in the two conditions. When the two interaural conditions were intermixed within blocks of trials, performance was slightly impaired in comparison to the situation in which the interaural condition remained constant throughout blocks of trials.

Acoustic Stimulation↗

PubMed1992

Herpes simplex virus type 1 latency-associated transcription unit promotes anatomical site-dependent establishment and reactivation from latency.

Defined herpes simplex virus type 1 (HSV-1) mutants KOS/1 and KOS/62 (positive and negative, respectively, for latency-associated transcripts [LATs]) express the Escherichia coli beta-galactosidase (beta-Gal) gene during latency. These mutants were employed to assess the functions of the latency-associated transcription unit on establishment and maintenance of and reactivation from the latent state. It was found that in the trigeminal ganglia, the frequencies of hyperthermia-induced reactivation of KOS/62 and an additional LATs- mutant (KOS/29) were reduced by at least 80%. Quantification of latently infected neurons expressing the beta-Gal gene revealed that the LATs- mutant KOS/62 established approximately 80% fewer latent infections in the trigeminal ganglia than did KOS/1 (LATs+). This reduction in establishment which is evident in the trigeminal ganglia could account for the reduced frequency of reactivation from this site. In striking contrast, both LATs- mutants reactivated with wild-type frequencies from lumbosacral ganglia. Quantification of beta-Gal-positive neurons at this site revealed that KOS/62 established as many as or more latent infections than the LATs+ virus, KOS/1. Colocalization of HSV antigen and beta-Gal suggested that the decreased establishment by LATs- mutants in trigeminal ganglia was the result of inefficient viral shutoff. Thus, one function of the HSV-1 LATs transcription unit is to promote the establishment of latency in trigeminal but not lumbosacral ganglia. Such a function may be relevant to understanding the distinct clinical recurrent disease patterns of HSV-1 and HSV-2.

Animals↗

PubMedDate not supplied

Acoustic reflex latency test in the evaluation of nontumor patients with abnormal brainstem latencies.

The acoustic reflex latency test (ARLT), an indirect measure of neural conduction time utilizing the electroimpedance method, was used to evaluate 43 highly suspect, nontumor patients who demonstrated abnormal latency results on brainstem electric response audiometry (BERA), false-positive for tumor. Normative values and criteria for tumor-positive ARLT results were established on a control group using a second generation test unit, comprised of dual impedance bridges and a digital signal averager, designed especially to perform the ARLT. When cut-off criteria for both absolute reflex latency and interaural latency difference (ILD) values were applied to this BERA false positive population, the ARLT correctly identified 93% of patients as having end-organ lesions. Differences in ARLT and BERA test results are attributed to differences in 1) method of measurement, 2) characteristics of the eliciting signal, and 3) generation of the response. These factors are discussed as sources of variability. Both ARLT and BERA are recommended as tandem procedures when screening for acoustic or angle tumors.

Audiometry↗

PubMed1989

Effects of hyperbaric environment on human auditory middle latency response (MLR) and short latency somatosensory evoked potential (SSEP).

Hyperbaric chamber dives at 19 ATA with helium-oxygen were performed at the Japan Marine Science Technology Center from November 15 to December 3 in 1988 and from January 25 to February 4 in 1989. During simulated underwater experiments, auditory middle latency responses (MLRs) and short latency somatosensory evoked potentials (SSEPs) were recorded in 3 professional divers (2 divers in each dive) for assessment of brain function. During the saturation dive (180 m below sea level) component Pa on MLR was lost, while component Po remarkably increased in amplitude. These MLR changes rapidly recovered between the beginning of decompression and at about 90 m below sea level. On the other hand, N9-N20 interpeak latency on SSEP slightly or moderately increased in the both divers, but N9-N14 interpeak latency was not affected by the 19 ATA saturation dive. These results suggest that the hyperbaric environment corresponding to 180 m below sea level cause some cerebral dysfunctions, probably between the brainstem and the cortex, but these dysfunctions are only transient.

Adult↗

PubMedDate not supplied

[The effect of the visual stimulation of the leading and nonleading eye on the value of the saccadic latency period and on the peak latency of rapid presaccadic potentials].

Visual targets were presented monocularly to the leading and nonleading eyes. The complex of rapid positive and negative potentials was studied using the reverse summation from the onset of saccades. The latencies of saccades and peak latencies of the averaged presaccadic potentials were measured. The dependence of the saccade latencies and peak latencies of the complex of potentials on stimulation of the leading or nonleading eye and saccade direction was not simple and was largely determined by the individual profile of asymmetry. It is suggested that during stimulation of the leading eye the processes of attention fixation and switching as well as of the space visual processing are faster than during stimulation of the nonleading eye. Thus, the leading role of the right eye is reflected not only in fixation processes but also in movement anticipation.

Adult↗

PubMed1990

[Short-latency and long-latency muscle reflex responses in man].

In a group of 70 healthy subjects the author examined repeatedly the reflex response from the m.interosseus dorsalis I during middle voluntary contraction of the muscle induced by electrical stimulation of the dermal branches of the nn. digitalis of the index finger. The aim of the reflexological investigation was analysis of some electrophysiological properties of short-latency (SL) and long-latency (LL) reflex responses which could be identified as excitation and inhibition modulations of the recorded muscular activity after rectification and averaging of the electromyogram. The results of the analysis revealed a constant intraindividual shape and latencies of the SL and LL components of the reflex responses (30 ms, 50 ms resp.), regardless whether one or several different frequencies of stimulation were used. The SL reflex response in the distal muscles of the upper extremity is compatible with the spinal loop; the latency of the LL response is shorter than the voluntary reaction time for the small muscles of the hand, therefore its reflex origin is assumed.

Adult↗

PubMed1995

[Long-term prolongation of direct pupillary light reflex latency and P100 latency of pattern visual evoked potential in unilateral optic neuritis].

We evaluated the visual functions of visual acuity, color sense, direct pupillary light reflex and pattern visual evoked potentials (P100) in five patients with unilateral optic neuritis whose visual acuity improved to 1.0 or better in order to assess the recovery of the impaired optic nerve fibers from the inflammatory process. During follow-up periods the direct light pupillary reflex was electropupillographically recorded and the P100 latency of visual evoked potentials was examined in both eyes. The temporal course of their differences showed a biphasic curve: the acute stage showed a rapid decrease of the differences and the chronic stage showed a flat line analysis of Pearson's correlation coefficient revealed that latency differences were mutually altered although there was a tendency for differences of direct pupillary reflex latency to decrease more rapidly at the acute stage than those of P100 latency. The present study demonstrated that the two different classes of the optic nerve fibers originating from the retinal ganglion cells, pupillary reflex-related fibers and form vision-related fibers, were damaged to the same degree by the inflammation, in spite of their morphological differences.

Adult↗

PubMed2001

The 2.2-kilobase latency-associated transcript of herpes simplex virus type 2 does not modulate viral replication, reactivation, or establishment of latency in transgenic mice.

To better understand the mechanisms responsible for the observed effects of deletions in the promoter region of the latency-associated transcript (LAT) gene in impairing herpes simplex virus (HSV) reactivation, we generated mice transgenic for a 5.5-kb HSV type 2 (HSV-2) genomic fragment spanning the major LAT, along with the LAT promoter and flanking regions, in the C57BL/6 background. The mice expressed abundant 2.2-kb major LATs in trigeminal ganglia (TG) and other tissues. The effects of the transgene on HSV-2 infection, latency, and reactivation were assessed. When infected with wild-type (WT) HSV-2 or its LAT promoter deletion (LAT(-)) mutant, primary lung fibroblast lines established from normal C57BL/6 and transgenic mice supported virus growth equally well. The replication of these viruses in the mouse eye and their spread to TG and brains were similar. The quantities of latent viral DNA in TG of transgenic and normal mice, as determined by real-time PCR, were comparable. UV light-induced reactivation of the LAT(-) mutant from transgenic mice (0 to 7%) was no more frequent than that from normal mice (0 to 14%), while WT virus was reactivated from 13 to 54% of normal mice and 22 to 54% of transgenic mice. The cumulative data indicate that, when expressed transgenically, the HSV-2 major LAT cannot influence HSV-2 infection or latency and cannot complement the defect in reactivation of the LAT(-) mutant. These results imply that the phenotype of reduced reactivation associated with the LAT(-) mutant is related to a function encoded in the LAT promoter but not to the major LAT itself.

Animals↗

PubMed2004

The varicella-zoster virus open reading frame 63 latency-associated protein is critical for establishment of latency.

Varicella-zoster virus (VZV) expresses at least six viral transcripts during latency. One of these transcripts, derived from open reading frame 63 (ORF63), is one of the most abundant viral RNAs expressed during latency. The VZV ORF63 protein has been detected in human and experimentally infected rodent ganglia by several laboratories. We have deleted >90% of both copies of the ORF63 gene from the VZV genome. Animals inoculated with the ORF63 mutant virus had lower mean copy numbers of latent VZV genomes in the dorsal root ganglia 5 to 6 weeks after infection than animals inoculated with parental or rescued virus, and the frequency of latently infected animals was significantly lower in animals infected with the ORF63 mutant virus than in animals inoculated with parental or rescued virus. In contrast, the frequency of animals latently infected with viral mutants in other genes that are equally or more impaired for replication in vitro, compared with the ORF63 mutant, is similar to that of animals latently infected with parental VZV. Examination of dorsal root ganglia 3 days after infection showed high levels of VZV DNA in animals infected with either ORF63 mutant or parental virus; however, by days 6 and 10 after infection, the level of viral DNA in animals infected with the ORF63 mutant was significantly lower than that in animals infected with parental virus. Thus, ORF63 is not required for VZV to enter ganglia but is the first VZV gene shown to be critical for establishment of latency. Since the present vaccine can reactivate and cause shingles, a VZV vaccine based on the ORF63 mutant virus might be safer.

Animals↗

PubMed1978

Factors that affect the amplitudes and latencies of the vertex short latency acoustic responses in the cat.

The latencies and amplitude of the short latency (less than 10 msec) acoustic evoked responses recorded from the vertex of the cat have been studied as a function of acoustic stimulus parameters. A change in the stimulus intensity, duration, or rate of repetition resulted in parallel changes in the first 5 evoked responses, i.e., the latencies shifted the same amount and the amplitudes were modified in the same proportion. Comparison of responses to monaural versus binaural stimuli indicated an occlusive effect of binaural stimulation only in potential 4.

Acoustic Stimulation↗

PubMed1984

The influence of click phase and rate upon latencies and latency distributions of the normal brain-stem auditory evoked potentials.

The effect of the phase of the click stimulus and its relation to the stimulus repetition rate on the brain-stem auditory evoked potentials (BAEPs) was investigated in 43 normal subjects, with condensation (C) and rarefaction (R) clicks of 10 and 50 Hz rate, using a piezoelectric headphone . The distribution of C and R latencies for component I seemed to be bimodal, probably reflecting (at least) two subcomponents in I separated by about 0.20 msec. C clicks tended to evoke the first and R clicks the second subcomponent. Condensation clicks gave significantly shorter absolute mean latencies for components I, IN, II, III, IIIN , IV and VI (10 Hz) and components IN, II, III, IIIN and IV (50 Hz). The V/I relative amplitude means were not influenced by phase, but increased with rate. Standard deviations were greatest for component IV latencies and increased only insignificantly with the higher repetition rate. A significantly smaller number of IV components was identified with R as compared to C clicks. Increasing the stimulus rate to 50 Hz detected wave IV in 12 of the 18 records where R clicks failed to identify IV with 10 Hz stimulation. The importance of the stimulus characteristics is discussed and some suggestions for clinical use of BAEP are made.

Adolescent↗

PubMed1995

Correlates of sleep latency on the multiple sleep latency test in a clinical population.

The multiple sleep latency test (MSLT) is commonly used as an objective measure of sleepiness. We retrospectively correlated MSLT scores from 147 patients with other information relating to sleepiness, namely demographic information, data from nocturnal polysomnograms (PSGs), and subjective assessments. The only variable that showed a valid and statistically significant correlation with the MSLT score was sleep latency on the PSG. The results were largely similar within subgroups focusing on (1) individuals with the ability to fall asleep on every nap, (2) subjects with abnormally short MSLT scores, (3) nap attempts that were successful, and (4) patients with particular diagnoses. We conclude that the mean sleep latency on the MSLT, in a clinical population, does not correlate well with a number of variables expected to influence sleepiness. While the validated utility of the MSLT in separating patients from normals or in identifying narcolepsy is not disputed, the accuracy of the MSLT as a measure of sleepiness appears to be limited.

Adult↗

PubMed2002

Short latency and long latency auditory evoked responses in children with attention deficit disorder.

INTRODUCTION: Children diagnosed with attention deficit disorder (ADD) can present with different abnormalities in electrophysiological studies. OBJECTIVE: The purpose of this paper is to compare brainstem auditory (short latency) evoked responses (BSAER) and long latency auditory evoked responses (LLAER) in school children with and without ADD. MATERIALS AND METHODS: A normative study was carried out, 20 normal subjects were studied. All these patients underwent a study protocol including BSAER and LLAER. Eighteen school children diagnosed as ADD were included in the active group. Eighteen school children were selected as controls. All children from both groups underwent BSAER and LLAER. BSAER and LLAER results from both groups of patients were compared. RESULTS: Brainstem transmission was significantly longer in children with ADD. The latency of P300 was significantly longer in children with ADD. Also, mean amplitude of P300 was significantly decreased in children with ADD. CONCLUSION: The results of this study indicates that school children with ADD show significant abnormalities in BSAER and LLAER. These electrophysiological procedures involving the auditory system can be useful for the diagnosis of children with ADD.

Adult↗

PubMed1999

Changes in long-latency reflexes onset latencies across full-wave rectified and non-rectified recordings.

Electrically elicited long-latency reflexes (LLRs) were obtained from thenar muscles by either fully rectified or non-rectified raw recordings in 10 healthy volunteers. The LLR II onset latencies were significantly (P < 0.0001) delayed on rectified (mean +/- SD: 49.8+/-2.9 ms) compared to raw (45.3+/-2.3 ms) recordings, with a mean difference of 4.4 ms. These data show that, according to the recording technique employed, the LLR II onset latencies can change considerably. The possible implications on cortical relay time (CRT) calculation and the understanding of the intracortical connections physiology are discussed.

Adult↗

PubMed1988

Fine mapping of the latency-related gene of herpes simplex virus type 1: alternative splicing produces distinct latency-related RNAs containing open reading frames.

The latency-related (LR) gene of herpes simplex virus type 1 (HSV-1) is transcriptionally active during HSV-1 latency, producing at least two LR-RNAs. The LR gene partially overlaps the immediate-early gene ICP0 and is transcribed in the opposite direction from ICP0, producing LR-RNAs that are complementary (antisense) to ICP0 mRNA. The LR gene is thought to be involved in HSV-1 latency. We report here the fine mapping and partial sequence analysis of this HSV-1 LR gene. 32P-labeled genomic DNA restriction fragments and synthetic oligonucleotides were used as probes for in situ hybridizations and Northern (RNA) blot hybridizations of RNA from trigeminal ganglia of rabbits latently infected with HSV-1. The two most abundant LR-RNAs appeared to share their 5' and 3' ends and to be produced by alternative splicing. These LR-RNAs were approximately 2 and 1.3 to 1.5 kilobases in length and were designated LR-RNA 1 and LR-RNA 2, respectively. Their 5' ends started approximately 1,210 nucleotides downstream from the 3' end of the ICP0 mRNA. Their 3' ends overlapped ICP0 by nearly 1,000 nucleotides. LR-RNA 1 appeared to have at least one intron removed, while LR-RNA 2 appeared to have at least two introns removed. The LR-RNAs contained two potential long open reading frames, suggesting the possibility that one or more of the LR-RNAs may be a functional mRNA.

Animals↗