Erhan Kiziltan

CONDUCTION VELOCITY DISTRIBUTION: EARLY DIAGNOSTIC TOOL FOR PERIPHERAL NEUROPATHIES

In order to get early information on the functional state of smaller myelinated fibers this article investigated the applicability of conduction velocity distribution on compound action potential recorded in experimentally demyelinated frog sciatic nerve. Conduction velocity distribution histograms were estimated by using the mathematical model the authors enhanced. The results suggest that by using appropriate conduction velocity distribution model the diagnosis time in demyelinating neuropathy may be shortened at least three times as compared with conventional conduction velocity assessment. Therefore, it may be concluded that a well-defined model designed for the estimation of the conduction velocity distribution may be used as a diagnostic tool for the early phase of peripheral demyelinating neuropathies.

Advanced Analysis of Finger-Tapping Performance: A Preliminary Study

BACKGROUND The finger-tapping test is a commonly employed quantitative assessment tool used to measure motor performance in the upper extremities. This task is a complex motion that is affected by external stimuli, mood and health status. The complexity of this task is difficult to explain with a single average intertap-interval value (time difference between successive tappings) which only provides general information and neglects the temporal effects of the aforementioned factors. AIMS This study evaluated the time course of average intertap-interval values and the patterns of variation in both the right and left hands of right-handed subjects using a computer-based finger-tapping system. STUDY DESIGN Cross sectional study. METHODS Thirty eight male individuals aged between 20 and 28 years (Mean±SD = 22.24±1.65) participated in the study. Participants were asked to perform single-finger-tapping test for 10 seconds of test period. Only the results of right-handed (RH) 35 participants were considered in this study. The test records the time of tapping and saves data as the time difference between successive tappings for further analysis. The average number of tappings and the temporal fluctuation patterns of the intertap-intervals were calculated and compared. The variations in the intertap-interval were evaluated with the best curve fit method. RESULTS An average tapping speed or tapping rate can reliably be defined for a single-finger tapping test by analysing the graphically presented data of the number of tappings within the test period. However, a different presentation of the same data, namely the intertap-interval values, shows temporal variation as the number of tapping increases. Curve fitting applications indicate that the variation has a biphasic nature. CONCLUSION The measures obtained in this study reflect the complex nature of the finger-tapping task and are suggested to provide reliable information regarding hand performance. Moreover, the equation reflects both the variations in and the general patterns associated with the task.

A HIGH-PRECISION, LOW COST SYSTEM FOR EVALUATING FINGER-TAPPING TASKS

Finger-tapping test is extensively employed to assess motor asymmetry in brain damaged patients and also to study the relationship between handedness and performance in normal subjects. The aim of this study was to develop a computer based finger-tapping system that could provide quantitative measures of finger-tapping performance. The system is designed to be used in a standard personel computer without the need of any other hardware. The software is written in Borland Delphi® 6.0 for Microsoft® Windows 98® and higher operating systems. Beginning with the Pentium® processor, it could be possible to access a time-stamp counter. The time-stamp counter is a 64-bit machine specific register that is incremented by every clock cycle, and keeps an accurate count of every cycle that occurs on the processor. By using a computer with 1 GHz processor speed it is possible to reach a high precision time resolution of 1 μs in finger-tapping tests. Our future prospects for the system are to improve it with various tools such as synchronized recording of electromyography, tapping force monitoring, monitoring of finger angle, and the response to different stimulus parameters by adding appropriate hardware and procedure.

DEEP PERONEAL MOTOR NERVE CONDUCTION VELOCITY DISTRIBUTION AND CORRELATION BETWEEN NERVE CONDUCTION GROUPS AND THE NUMBER OF INNERVATED MUSCLE FIBERS

In this study, the distribution of peroneal-nerve conduction velocity was studied in 17 normal subjects, using the collision method. Paired supramaximal stimuli with predetermined interstimulus intervals (ISI) were applied at distal and proximal points of peroneal nerve and the resultant compound muscle action potentials (CMAPs) were recorded. The change in CMAP amplitudes and areas with ISI were deduced, and the relative number of fibers corresponding to each conduction velocity group (CVG) were computed. Conduction velocities of the peroneal motor nerve innervating the Extensor Digitorum Brevis (EDB) muscle were found to be in the range of 28-52 m/s and CVG innervating the greatest number appears to be in 40-48 m/s range, which consists of 70% of all fibers. These results show that, compared with the median motor nerve, deep peroneal motor nerve that innervates the EDB muscle consist of slow fibers.

Axonal excitability and conduction alterations caused by levobupivacaine in rat

Abstract In this study, effects of the long-acting amide-type local anesthetic levobupivacaine on axonal conduction and excitability parameters of the rat sciatic nerve were thoroughly examined both in vitro and in vivo. In order to deduce its effects on isolated nerve conduction, compound nerve action potential (CNAP) recordings were performed using the suction method over sciatic nerves of Wistar rats before and after administration of 0.05 % (1.7 mmol L−1) levobupivacaine. Levobupivacaine caused complete CNAP area and amplitude depression by blocking conduction in a time-dependent manner. To assess the influence of levobupivacaine on in vivo excitability properties, threshold-tracking (TT) protocols were performed at sciatic nerves of rats injected with perineural 0.05 % (1.7 mmol L−1) levobupivacaine or vehicle alone. Charge-duration TT results revealed that levobupivacaine increases the rheobase and decreases the strength-duration time constant, suggesting interference of the anesthetic with the opening of Na+ channels. Twenty and 40 % threshold electrotonus curves were found for both groups to follow the same paths, suggesting no significant effect of levobupivacaine on K+ channels for either the fastest or relatively slow conducting fibers. Current-threshold relationship results revealed no significant effect on axonal rectifying channels. However, according to the results of the recovery cycle protocol yielding the pattern of excitability changes following the impulse, potential deviation was found in the recovery characteristics of Na+ channels from the absolute refractory period. Consequently, conduction blockage caused by levobupivacaine may not be due to the passive (capacitive) properties of axon or the conductance of potassium channels but to the decrease in sodium channel conductance.

Polyphasic Temporal Behavior of Finger-Tapping Performance: A Measure of Motor Skills and Fatigue

ABSTRACT Successive voluntary motor movement involves a number of physiological mechanisms and may reflect motor skill development and neuromuscular fatigue. In this study, the temporal behavior of finger tapping was investigated in relation to motor skills and fatigue by using a long-term computer-based test. The finger-tapping performances of 29 healthy male volunteers were analyzed using linear and nonlinear regression models established for inter-tapping interval. The results suggest that finger-tapping performance exhibits a polyphasic nature, and has several characteristic time points, which may be directly related to muscle dynamics and energy consumption. In conclusion, we believe that future studies evaluating the polyphasic nature of the maximal voluntary movement will lead to the definition of objective scales that can be used in the follow up of some neuromuscular diseases, as well as, the determination of motor skills, individual ability, and peripheral fatigue through the use of a low cost, easy-to-use computer-based finger-tapping test.

Semi-automatic scoring tool for comet assay

Comet assay or single-cell gel electrophoresis is a widely used method for DNA damage assessment. The results of the method can be scored under microscopic examination either with the naked eye or by automated systems. In this study, we present a semi-automatic comet assay analysis tool that was developed in our laboratory. The results obtained with our tool were compared with that of fully automatic shareware software. The preliminary results suggest that the presented semi-automatic software is an accurate and reliable tool for evaluation of comet assay.

SEXUAL DEPENDENCY OF RAT SCIATIC NERVE FIBER CONDUCTION VELOCITY DISTRIBUTIONS

Gender differences, either with the structural or through with hormones, dictate how the corresponding organ or organ system responses to physiological signals. Current study aims to investigate gender dependent differences in conduction related parameters of rat sciatic nerve. Compound action potentials (CAP) were recorded via suction electrode whereas the conduction velocity distributions (CVD) were performed using the method known as collision technique in the literature. Studied CAP parameters, namely conduction velocities (CV), area of the CAPs and time required to reach the maximum depolarization (TP) have been found significantly different for female and male rats. Detailed analyses have shown that sex dependent differences were more remarkable in the right leg responses of female and male rats. Additionally, CVDs indicate that the number of fibers having CVs between 5–30 m/s is much more in male right sciatic nerve trunk when compared to age matched female rats. The present study, for the first time clearly shows that shift in the contribution of nerve fibers to lower CVs is the main causal of the sex dependent differences seen in rat sciatic nerve fibers.

ASSESMENT CRITERIA FOR EXPERIMENTAL DEMYELINATION INDUCED IN FROG PERIPHERAL NERVE

In ideal conditions the area under compound action potential may be used as an index for the number of activated fibers in a nerve trunk whereas peak amplitude, maximum time derivative, and duration may be used as an indicator for the rate of contribution to compound action potential and the degree of velocity dispersion. In this study, the time domain effect of demyelination on compound action potential has been investigated in experimentally demyelinated frog sciatic nerve. The results were analyzed in order to suggest criteria for demyelination. The results suggest that the changes in peak amplitude and maximum time derivative of compound action potential that is made up by the contribution of the active fibers may be more useful in the assessment of early phase of demyelination. Therefore, it may be concluded that these two parameters, intrinsically, carry augmented information on the velocity dispersion originated from larger-diameter fibers.