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Latency Differences (latency + difference)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Simplified orthodromic inching test in mild carpal tunnel syndrome

MUSCLE AND NERVE, Issue 12 2001
Paul Seror MD
Abstract This prospective study was undertaken to determine the clinical relevance, reliability, sensitivity, and specificity of the orthodromic inching test with 2-cm incremental study of the median nerve over the four intracarpal centimeters in 50 control and 50 successive (unselected) patient wrists with mild carpal tunnel syndrome (CTS). In controls, the mean maximum conduction delay per 2 cm (CD/2cm) was 0.445 ± 0.04 ms, and abnormality was defined as at least one CD/2cm exceeding the mean + 2.5 SD of the normal CD/2cm. This yielded a specificity of 98%. In patients with mild unselected CTS, this simplified orthodromic inching test (SOIT) detected the median nerve lesion at the wrist in 47 cases (sensitivity = 94%). The SOIT detected 15 more CTS cases than did the orthodromic median-ulnar latency difference of the 4th digit (Chi square = 13; P = .002). Thus, the SOIT was as effective as an incremental study every centimeter over 10 cm, and the time required for the test allows its routine use when other electrodiagnostic tests fail to reveal any median nerve impairment. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1595,1600, 2001 [source]

Stimulated single fiber electromyography in the mouse: Techniques and normative data

MUSCLE AND NERVE, Issue 7 2001
Clifton L. Gooch MD
Abstract As the number of new transgenic mouse models of human neuromuscular disease continues to increase, the development of sophisticated electrophysiologic techniques for assessing the peripheral nervous system in these models has become important. Neuromuscular junction (NMJ) dysfunction, in particular, is often not detectable by morphologic or other techniques. To enable sensitive testing of murine NMJ function, we developed and tested a method for stimulated single fiber electromyography (S-SFEMG) in the gastrocnemius muscles of anesthetized mice. Jitter was assessed by measuring the mean consecutive latency difference (MCD) of single fiber responses to sciatic nerve stimulation at 2 HZ. Mean MCD values in normothermic mice were in the range of 6,8 ,s for different strains, with no MCD values exceeding 25 ,s. Reduced core temperature (to 29°,30°C) resulted in increased jitter, whereas intubation and mechanical ventilation of mice did not alter these values. Intraperitoneal and intravenous injection of vecuronium, however, resulted in progressively increased jitter followed by blocking in continuously monitored fibers. These observations validate the utility of S-SFEMG in mice as an index of NMJ function under a variety of physiologic conditions, and suggest that a high safety factor for neuromuscular transmission exists at mouse NMJs. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 941,945, 2001 [source]

Disparity of activation onset in sensory cortex from simultaneous auditory and visual stimulation: Differences between perfusion and blood oxygenation level-dependent functional magnetic resonance imaging

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2005
Ho-Ling Liu PhD
Abstract Purpose To compare the temporal behaviors of perfusion and blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in the detection of timing differences between distinct brain areas, and determine potential latency differences between stimulus onset and measurable fMRI signal in sensory cortices. Materials and Methods Inversion recovery (IR) spin-echo echo-planar imaging (EPI) and T2*-weighted gradient-echo EPI sequences were used for perfusion- and BOLD-weighted experiments, respectively. Simultaneous auditory and visual stimulations were employed in an event-related (ER) paradigm. Signal time courses were averaged across 40 repeated trials to evaluate the onset of activation and to determine potential differences of activation latency between auditory and visual cortices and between these scanning methods. Results Temporal differences between visual and auditory areas ranged from 90,200 msec (root-mean-square (RMS) = 134 msec) and from ,80 to 930 msec (RMS = 604 msec) in perfusion and BOLD measurements, respectively. The temporal variability detected with BOLD sequences was larger between subjects and was significantly greater than that in the perfusion response (P < 0.04). The measured time to half maximum (TTHM) values for perfusion imaging (visual, 3260 ± 710 msec; auditory, 3130 ± 700 msec) were earlier than those in BOLD responses (visual, 3770 ± 430 msec; auditory, 3360 ± 460 msec). Conclusion The greater temporal variability between brain areas detected with BOLD could result from differences in the venous contributions to the signal. The results suggest that perfusion methods may provide more accurate timing information of neuronal activities than BOLD-based imaging. J. Magn. Reson. Imaging 2005;21:111,117. © 2005 Wiley-Liss, Inc. [source]

Brain electrical correlates of dimensional weighting: An ERP study

PSYCHOPHYSIOLOGY, Issue 2 2007
Klaus Gramann
Abstract In visual search, there is a reaction time (RT) cost for targets on a given trial if the previous target was defined in a different dimension. According to the "dimension-weighting" account (Müller, Heller, & Ziegler, 1995), limited attentional weight needs to be shifted to the new dimension, resulting in slower RTs. The present study aimed at identifying brain electrical correlates associated with the weight shift. Analyses of ERPs revealed several components to reflect dimension changes whether the task was to detect the target or to identify its defining dimension. N2 amplitudes were more negative whenever the dimension changed. The P3 exhibited latency differences that mirrored RTs in both tasks, but the amplitudes showed no direct relation to stimulus- or response-related processes. Finally, slow-wave amplitudes were enhanced for dimension changes. Taken together, the results provide support for relatively early, perceptual processes underlying dimension change costs. [source]

MEG detection of delayed auditory evoked responses in autism spectrum disorders: towards an imaging biomarker for autism

AUTISM RESEARCH, Issue 1 2010
Timothy P.L. Roberts
Abstract Motivated by auditory and speech deficits in autism spectrum disorders (ASD), the frequency dependence of superior temporal gyrus (STG) 50,msec (M50) and 100,msec (M100) neuromagnetic auditory evoked field responses in children with ASD and typically developing controls were evaluated. Whole-cortex magnetoencephalography (MEG) was obtained from 17 typically developing children and 25 children with ASD. Subjects were presented tones with frequencies of 200, 300, 500, and 1,000,Hz, and left and right STG M50 and M100 STG activity was examined. No M50 latency or amplitude Group differences were observed. In the right hemisphere, a Group×Frequency ANOVA on M100 latency produced a main effect for Group (P=0.01), with an average M100 latency delay of 11,msec in children with ASD. In addition, only in the control group was the expected association of earlier M100 latencies in older than younger children observed. Group latency differences remained significant when hierarchical regression analyses partialed out M100 variance associated with age, IQ, and language ability (all P -values <0.05). Examining the right-hemisphere 500,Hz condition (where the largest latency differences were observed), a sensitivity of 75%, a specificity of 81%, and a positive predictive value (PPV) of 86% was obtained at a threshold of 116,msec. The M100 latency delay indicates disruption of encoding simple sensory information. Given similar findings in language impaired and nonlanguage impaired ASD subjects, a right-hemisphere M100 latency delay appears to be an electrophysiological endophenotype for autism. [source]