| The research of Steady-State Visual Evoked potential(Steady State Visual Evoked Potential,SSVEP)has become a hotspot in the field of brain-computer interface and medicine.However,at present,the relative researches are mainly confined to the laboratory,and there is still a long way to go before the practical application.One of the main reasons is the lack of universality of these applications.As the moisture content of the visual cortex neuron membrane of different age groups is different,the equivalent capacitance and conductance of the corresponding membrane are also different,which makes the spatial electric field of the brain induced by the same light stimulation.And SSVEP is especially different between the elderly and adolescents.Although there have been a few published research results on SSVEP differences between the elderly and the young,the experimental contents and conditions of different teams differ greatly,and the experimental results are less repeatable,which brings great difficulties in summarizing and summarizing the influence law of age factor changes on SSVEP through the experimental results.Therefore,the influence of age on SSVEP and its ? wave property should be discussed theoretically.In this way,it can effectively guide people of different ages to collect SSVEP signals and improve the accuracy of their use of SSVEP-based brain-computer interface and clinical medical application system.Therefore,this paper used theoretical simulation and experimental methods to study the effects of age parameter changes on SSVEP and its stationary waves.The specific research work is as follows:1.The characteristics of neuron membrane ion channel differ across different age groups.Even for the same person,the balance potential of neuron ion channel will change with the increase of age.In this paper,based on the hodgkin-huxley equivalent circuit model of neuron,under the same external stimulation condition,the relationship between the equilibrium potential of neuron membrane ion channel and the action potential of neuron membrane release in different age groups was studied through simulation,so as to preliminarily understand the influence rule of age parameter changes on neuron membrane potential.The simulation results show that when the absolute value of equilibrium potential decreases,the peak value of action potential decreases.When the absolute value of ion channel equilibrium potential drops to a certain degree,the change of neuron membrane potential cannot exceed the threshold value of induced action potential.The visual cortex neuron membrane ion channel balance potential depends on the plasma concentration of sodium and potassium ion channels,and membrane ion concentration is closely related to a person's age,therefore,presumably in other physiological conditions and external stimulation case,same age factors to determine whether the membrane of neurons action potential size,distribution and action potential peak of SSVEP will also vary.For the elderly and young people,the difference is more obvious.2.The variation characteristics of SSVEP in different brain regions in the young and elderly groups were studied,and the Wilconxon symbol rank test was used to analyze the mean SSVEP amplitude in the young and elderly groups.The results showed that the SSVEP amplitude of the elderly group was lower than that of the young group under the same flickering stimulation,no matter in the occipital region or the parietal occipital region,and the difference was statistically significant,indicating that the change of age factor had a greater impact on SSVEP.3.Hilbert transform was used to calculate the instantaneous phase of alpha SSVEP and flickering signals.The phase difference of the two signals was used to calculate the degree of synchronization,which was valued as normalized Shannon entropy.The effects of age factors on alpha SSVEP entrainment were researched by experiments.Results show that under the same test conditions,although the two age groups alpha level of synchronization are "Arnold tongue" change rule,namely the ±3Hz?2 ±3Hz?4 ±3Hz frequency range,the center frequency of SSVEP alpha highest level of synchronization,the both sides showed a trend of gradual decline,but the degree of alpha synchronous elderly group are lower than the young.The experimental results also further indicate that age has an effect on the variation characteristics of SSVEP.4.The experimental results and simulation in this paper show that the SSVEP variation characteristics of the elderly and young people are quite different under the same external stimulus conditions.Both the amplitude of SSVEP and the degree of phase synchronization of its alpha wave and stimulus signal were lower in the elderly than in the young.These results help to further deepen the understanding of the electrophysiological characteristics of brain aging and provide some meaningful theoretical and experimental basis for clinical medicine and treatment. |
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