Research And Signal Analysis Of Functional Nerve Injury In Rats Based On Power-electric Effect

The issue of personal disability resulting from road traffic accidents has been the focus of national and international researchers.Every year,tens of millions of people worldwide are disabled by traffic accidents.Craniocerebral injury caused by traffic accidents has become one of the major causes of serious threat to human health,and craniocerebral injury is also a major cause of death and disability in traffic accidents.Due to the difficulty of obtaining regular brain tissue samples that can be used for experiments,even those obtained by cutting are difficult to guarantee the health,integrity and consistency.Considering the physiological similarity of nerve tissue disease,the sciatic nerve of rat is used as the object of this study.This paper topic is dedicated to the study of primary functional neurological damage to brain tissue due to strain/strain rate loading in traffic accidents.The subject is the sciatic nerve of SD rats.Based on the force-electric effect,the nerve electrical signals characterising the functional properties of the nerve are analysed in the time domain,frequency domain and time-frequency domain in a step-by-step progression.The study investigates the mechanism of neurofunctional injury of nerve fibers under different strain/strain rates,and provides a data basis for the next step of exploring the development of functional nerve injury tolerance index.The main research contents and conclusions are as follows:1)Construction of a model for mechanical injury and electrical testing detection of the sciatic nerve in rats.The existing force-electric effect platform is used as a basis for determining the strain/strain rate loading method based on experimental parameters.Based on known finite element simulation experiments to obtain the maximum strain/strain rate of brain tissue during vehicle-human collisions at different vehicle speeds,several sets of typical strain/strain rate values were selected and loaded onto the sciatic nerve of rats,and the distal nerve compound action potentials were obtained while proximal stimulation was performed on the nerve before and after the injury.2)Explore the relevant boundary conditions.As the electrode spacing when measuring compound nerve action potential can have an affect on the results,the optimal distance between the electrodes was experimentally screened.In order to keep the position of the nerve in the shield box twice before and after the experiment,methylene blue marker was used to dye the electrode position of the nerve stem,so the effect of methylene blue marker on the compound action potential of the nerve stem was explored.Conclusion:The electrode spacing for vitro recording of the rat sciatic nerve CNAP should be set to:0.5 cm distance between stimulus and stimulation electrodes;1cm distance between stimulus and recording electrodes;1.5 cm distance between recording and recording electrodes.The electrode placement of the nerve trunk was stained using methylene blue marker,and the methylene blue stain had little or no effect on the CNAP.3)According to the known finite element simulation experiment data of car-person collision,nine sets of strain/strain rate injury-causing parameters were selected to apply20s^-1,30s^-1and 40s^-1 strain rates to the nerve at three given strains,i.e.6%,9%and 12%,respectively,to damage the nerve,and the signal changes of the compound nerve action potential before and after the injury were investigated.And the composite nerve action potentials before and after the injury were analyzed in the time domain,frequency domain and time-frequency domain respectively.Finally,the relationship between the strain-strain rate product and the decrease in the wave amplitude of the nerve compound action potential was explored and studied.Conclusion:In the time domain,under the same strain condition,as the strain rate increases,the greater the proportional decrease in wave amplitude,the greater the proportional increase in time travel and the greater the proportional decrease in conduction velocity.In the frequency domain,within the 1k Hz cutoff frequency,the CNAP spectrum after damage is shifted towards the lower frequency band.The peak of the spectrum decreases after the pulling injury,and there is a corresponding decrease in the frequency corresponding to the peak.The proportion of low frequency component of CNAP increases.In the time-frequency domain,the time of action of the CNAP high-frequency signal after injury was significantly reduced,and the time of action of the low-frequency signal was significantly increased.The experimental results showed that CNAP signal changed significantly in the time domain,the frequency domain,and the time-frequency domain after nerve injury.In addition to strain,nerve stretch injury is also related to strain rate and the degree of nerve function loss gradually increased with increasing strain and strain rate.4)A curve is synthesized by the product of strain and strain rate and the amplitude drop ratio before and after the nerve compound action potential injury by Logistic function,and the corresponding mathematical relation is obtained.The experimental results shows that the Product of strain and strain rate has a certain relationship with the amplitude drop ratio of compound nerve action potentia.5)The experimental results obtained by using bullfrog sciatic nerve and rat sciatic nerve as different research objects were compared and analyzed.Conclusions:Firstly,the rat,as a mammal,has chemical synapses containing transmitters,which are not the same type of electrical synapses as those of the bullfrog.Secondly,the legs of bullfrogs are relatively more developed than those of rats,and longer samples of bullfrog sciatic nerve trunks were obtained.Thirdly,the recording-recording electrode spacing was 2.5cm when measuring compound action potentials in bullfrogs and 1.5cm when measuring compound action potentials in rats.Fourth,when the nerve trunk was injured at a certain strain-strain rate,the changes in amplitude,time course,and conduction velocity of the compound nerve action potential in bullfrogs were smaller than those of the compound nerve action potential in the rat sciatic nerve.Fifthly,the product of strain and strain rate were fitted to a logistic function to form a curve with the proportional decrease in wave amplitude before and after injury,and there was a significant difference between the two curves.In small strain/strain rate injuries,the bullfrog sciatic nerve showed a small increase in wave amplitude after the distraction injury,which has not been found in experiments using the rat sciatic nerve as a study subject.In summary,this paper established a model of sciatic nerve pulling injury and force electrical effect in SD rats,and initially explored the relationship between mechanical parameters of nerve injury and changes in nerve compound action potential.By fitting the strain-strain rate product to a logistic curve with the proportion of the wave amplitude decrease before and after the neural compound action potential injury,a preliminary mathematical model of the injury was established,which can better characterize the relationship between the degree of functional neural injury and the product of the loaded strain-strain rate,and contribute to the expansion of crash biomechanics research into the field of functional neural injury.It can also provide experimental data support for exploring the development of functional neurological injury tolerance indexes,and provide experimental basis and data support for further exploring the biomechanical mechanisms of traffic injuries.