Nonlinear Analysis Of Interspike Intervals Of Globus Pallidus In MPTP-treated Monkeys

Parkinson's disease (PD) is the most common movement disorder in the elderly. Its main manifestations are tremor, akinsia, rigidity, and postural instability. The underlying pathology of PD and MPTP-induced parkinsonism is a loss of midbrain dopaminergic neurons. Previous work revealed changes in the activity of globus pallidus (GP) neurons of MPTP-treated monkeys as compared with healthy ones, and the only finding was that the firing rates of GPi increased, whereas GPe cells displayed decreased firing rates. No more information about PD was shown. Many physiologists believe that the mode of the neural code is mean rate code which has been proved by many researches. However, this mode has many limitations such as too simple, low efficiency, less information et al. The frequence code theory has shown its limitation while the nonlinear theory and time code are popular and play a great role in neuroscience research in nowdays. In this essay we will use a new way to analysis the electrophysiological character of neuron of globus pallidus in monkeys.. ObjectiveAnalysis ISIs of different parts of globus pallidus in monkeys before and after treated by MPTP by methods derived from nonlinear dynamics and open out the relationship between PD and the electrophysiological character of neuron of globus pallidus.Methods(1)MPTP were injected directly into arteria carotis interna of the monkeys by means of endovascular to make PD models.(2)Record the discharges of GPi and GPe neurons (before and after surgery) for at least 180s, and the data is stored in hard disk.(3)Identify and select the single-unit discharge based on the amplitude, frequency and pattern. Only the single-unit discharge neurons would be studied. The neurons are located by identifying the typical neuron discharge of Gpe, Gpi and lamina between Gpe and Gpi and compared with the standard atlas.(4) Demarcate the spikes after operation and set up trains of Interspike Intervals. Calculate the firing rates before and after apomorphine was injected.(5) Calculate the UPO, Wavelet Entropy and the distribution mode of the ISIs of the GPi by nonlinear methods.(6) Compare the nonlinear index in (5) between healthy and PD monkeys and extract information which have relation with PD.Results(1) Making Parkinsonism monkeys by means of endovascular is a more safe, and simple method. An precise dose of MPTP can be injected into monkey painlessly and the monkey may recover in a short time.(2) The firing rates of GPi increased, whereas GPe cells displayed decreased firing rates when the monkey were treated by MPTP. The firing rates decrease when monkey were treated with apomorphine.(3) The charge mode was more regular in Parkinsonism monkey's GPi neurons than healthy ones, while no changes were found in ISIs of GPe neuron. An oscillation about 1~3Hz was found in the ISIs of GPi neuron.(4) ISIs of GPi neuron can be detected UPOs 1,2,3 orbit.(5) Wavelet Entropy of GPi ISIs increase after monkeys were treated with MPTP, which show high diversity in Parkinsonism monkeys.ConclusionThe results above demonstrate that the ISIs of globus pallidus in parkinson's disease are chaotic. Many nonlinear research methods can be used to study the electrophysiology of Parkinsonism basal ganglia. Gpi is more close to the mechanism of PD compared with GPe.