| Spiral wave is a common self-organizing wave that occurs when the system moves out of equilibrium,causing arrhythmias in the heart tissue that can lead to sudden cardiac death.In addition to the cardiac system,the presence of spiral waves has also been observed by numerical modeling or in the isolated cerebral cortex,but the role of spiral waves in the nervous system is not clear.As the spatial pattern organizer or oscillation rhythm generator of population neurons,spiral wave plays a positive role in regulating local electrical activity in the cortex,participating in the oscillation and functional processing of the cerebral cortex in living mammals,and enhancing the consistency of spatial activity of neurons.Both sleep and epilepsy have active neuronal electrical activity in the brain.The former is a physiological state,and the latter is a pathological state,which is an important choice for the study of spiral waves.The purpose of this study is to investigate the morphological and distribution characteristics of spiral waves in the cerebral cortex of rats in sleep-like physiological state and in the pathological state of absence epilepsy,and to reveal the physiological significance of spiral waves in different sleep stages,the mechanism of spiral waves participating in the spontaneous termination of absence seizures,and the possible mechanism of partial activation of cerebral cortex in absence epilepsy.This study aims to understand the pathological mechanism of epilepsy from a new perspective of spiral wave and to provide a basis for the treatment and efficacy evaluation of refractory epilepsy.Part 1:Characteristics of cortical spiral wave in sleep-like physiological state in ratsObjective:To investigate the characteristics of spiral waves in the cerebral cortex of rats during different sleep periods in sleep-like physiological state,and to further explore the possible physiological significance of spiral waves.Methods:Twelve healthy male Wistar rats were subjected to skull surgery,cortical staining and voltage-sensitive dye(VSD)imaging.The rats were continuously pumped with sodium pentobarbital to induce a sleep-like physiological state.The cortical electroencephalogram,electrocardiogram and VSD imaging were collected simultaneously,each acquisition period(trial)was 5 seconds,and at least 15 trials were collected for each rat during each sleep period.According to the characteristics of different stages of sleep-wake in rats,the sleep-like physiological state of rats was divided into NREM stage and REM stage.The morphology of spiral wave in the cerebral cortex was recorded in different sleep stages,and the frequency and duration of spiral wave in NREM stage and REM stage were compared.According to the rhythm morphology and proportion of θ wave on EEG,the REM period of rats was further divided into three periods,namely regular θ period,irregular θ period and low-amplitude θ transition period.The frequency of spiral wave in different periods of REM was compared and analyzed.The frequency of spiral waves was expressed as Ratio,that is,the number of spiral waves in each trial=the number of spiral waves in each trial/the number of trials.At the same time,the Fourier transform program based on Matlab was used to obtain the θ/δ amplitude ratio,and the number distribution and duration characteristics of spiral waves under different θ/δ amplitude ratios were analyzed.Results:1.In the sleep-like physiological state of rats,spiral waves were observed in both NREM and REM phases.2.The average number of spiral waves per trial(Ratio)in NREM was 1.9±0.2/trial,and that in REM was 0.9±0.3/trial.The frequency of spiral waves in NREM was significantly higher than that in REM(p<0.001).3.The average duration of single spiral wave was 53.6±19.8 ms in NREM and 50.4±19.8 ms in REM.There was no significant difference in the average duration of single spiral wave between NREM and REM(p>0.05).4.In different stages of REM,the Ratio of low-amplitude θ transition period and irregular θ period was 2.3±0.2/trial and 0.7±0.1/trial,respectively.There was no spiral wave in the regular θ period in 39 trials.In REM,the difference in the frequency of spiral waves in different periods was statistically significant(p<0.001),and the frequency of spiral waves was the highest in the transition period of low-amplitude θ wave.5.Each trial lasted for 5 seconds.After time conversion,the frequency of spiral wave was about 0.38/s in NREM stage,0.18/s in REM stage,0.46/s in low-amplitude θ transition period,0.14/s in irregularθ period,and 0/s in regular θ period in REM stage.6.According to the θ/δ amplitude ratio,the number of spiral waves in NREM was significantly higher than that in REM.When the θ/δ amplitude ratio was 0.6-0.8,the number of spiral waves was the highest(372),accounting for 60.7%of the total number in NREM.The single spiral wave duration was longest(77.2 ms)when the θ/δ ratio was 0.4-0.5,and then decreased with the increase of the θ/δ ratio.Conclusions:1.In the sleep-like physiological state of rats,the frequency of spiral waves during NREM is high.When the regularity of cortical electrical activity is poor and δ wave is dominant,spiral wave is easy to produce,suggesting that it is related to thalamic-cortical electrical activity.2.During REM,the spiral wave appears most frequently in the low-amplitude transition period between the continuous regular θwaves,which may play an important role in the initial or conversion process of the θrhythm during sleep.Part 2:Characteristics of spiral waves in the cortex of rats in absence epilepsy and the mechanism involved in spontaneous termination of seizuresObjective:To observe the morphology,number and duration of spiral waves in the cerebral cortex of rats with absence epilepsy,and to explore the mechanism of spiral wave formation in the cortex and its involvement in the spontaneous termination of seizures.Methods:Twelve healthy male Wistar rats were subjected to skull surgery,cortical staining and VSD imaging.The rats were anesthetized with fentanyl and haloperidol to maintain a static state.The absence epilepsy model was established by intraperitoneal injection of y-butyrolactone.The absence epileptic state of rats was divided into five stages:background stage(BS)before γ-butyrolactone administration,discharge coming stage(DCS),during discharge stage(DDS),discharge ending stage(DES)and interictal stage(IS).Cortical electroencephalogram,electrocardiogram and VSD imaging were simultaneously collected,and each acquisition period(trial)was 10s,and at least 6 trials were collected in each period for each rat.The frequency and duration of spiral waves in 5 different periods were compared,and the morphology of spiral waves in absence epilepsy state of rats was recorded.Results:1.Combined anesthesia with haloperidol and fentanyl caused spike and slow waves in electroencephalogram of some rats.2.The phase map of the continuous evolution of 6 spiral waves in the cerebral cortex of rats with absence epilepsy was shown.It was found that multiple sites in the local cortex are activated asynchronously,which was easy to produce spiral waves.It was also found that the wave front of spiral wave was compressed.3.The lowest frequency of spiral wave was found in the BS and IS in absence epileptic rats(Ratio:0.17±0.04 vs 0.16±0.04/trial).In the beginning,process and termination stages of typical spike and slow wave discharges,the frequency of spiral wave gradually increased,and the frequency of spiral wave was the highest in the DES(Ratio:2.01 ±0.13/trial).4.There was no significant difference in the duration of single spiral wave among the five different stages in the rats with absence epilepsy(p>0.05).Conclusions:1.In absence epilepsy of rats,spiral waves appears most frequently during the transition stage between the discharges and stopping of spike and slow waves,which is involved in the transition process of absence epilepsy and post-seizure state,and helps the cerebral cortex to transition from seizure state to stable state.It may be an important activity pattern of cortical population neurons to control the spontaneous termination of seizures at the fluid dynamics level.2.The spiral wave interferes with the pathological oscillation of the epileptic excitation wave(～3 Hz)with its own natural frequency(about 10 Hz),so that the seizures stop spontaneously and avoid the evolution into status epilepticus.3.The formation of spiral wave may be related to the asynchronous activation of multiple sites in the local area of the cerebral cortex,and the sites are not in the refractory period,and then the electric fields interact with each other,and finally form spiral wave,which is conducive to the synchronization of the electrical activity of cortical neurons in a short time.Part 3:Voltage sensitive dye imaging analysis of polyspike and slow wave complex in rats with absence epilepsyObjective:To study the VSD imaging characteristics of single-spike and double-spike slow waves in absence epilepsy rats,and to explore the possible mechanism of partial activation of the cerebral cortex in absence epilepsy.Methods:According to the second part of the experiment,eight healthy male Wistar rats were used to induce absence epilepsy model with y-butyrolactone,and cortical electroencephalogram(EEG)and VSD imaging were collected simultaneously.The EEG was used to distinguish the single-spike slow wave and double-spike slow wave.The spatio-temporal patterns and X-T plot characteristics of synchronous VSD imaging were analyzed.The spatio-temporal patterns of VSD imaging under different morphologies of spike and slow waves were analyzed,and the possible role of spiral waves was analyzed.At the same time,video-EEG recordings of 10 absence epilepsy patients were collected,and 100 double-spike slow waves were randomly selected from both humans and rats.The time interval between spike components(PSI)of double-spike slow waves were analyzed.Results:1.In the spatiotemporal pattern of VSD imaging in rats with absence epilepsy,single-spike slow wave activated the entire cerebral cortex of the imaging field,while each spike component of double-spike slow wave alternately activated adjacent regions of the cerebral cortex.2.On the X-T map drawn by the VSD signal,the single-spike slow wave invaded the whole imaging field,while the double-spike slow wave had obvious time delay during the two partial activation.The activation boundary might be related to the V1/V2 boundary of the visual area.The location of the activation boundary was similar in the same rat,but different rats had different activation boundaries.3.In absence epilepsy of rats,spikes have different shapes,and the corresponding spatio-temporal patterns of VSD imaging were also different,and spiral waves could be observed.4.The appearance of spiral wave can end the asynchronous activation of different regions of cerebral cortex.5.There are polyspike and slow wave complex in the EEG of epileptic patients as well as rats,and the number,waveform and amplitude of spike slow waves were related to different locations of EEG acquisition.6.There was no significant difference in the PSI between epileptic patients and rats(36.1 ±9.6 ms vs 36.7±7.4 ms,p>0.05).Conclusions:1.In absence epilepsy of rats,there are different cortical activation patterns between single-spike slow wave and double-spike slow wave.The spike-wave components of double-spike slow wave alternately activate the cerebral cortex in a "half and half" pattern.2.The spiral wave in double-spike slow wave can resynchronize the different activation states of the cerebral cortex,improve the consistency of the electrical activity of cortical neurons,and avoid the cortical dysfunction caused by the asynchronous activity.3.The generation of double-spike slow wave in absence epilepsy rats may be related to the existence of a certain region of cerebral cortex with strong feedforward inhibition. |
PDF Full Text Request