The Research For The Spike And Wave Effects On Dynamics Of Theta Rhythm

Epilepsy is a dynamical disease in the brain systems. The effect of epilepsy on cognition is one of important work in neuron-science whose goal is to improve the life quality of epileptic patients. But the underlying mechanisms of epileptic effects on cognition remain unknown. So here, by using the depth electroencephalogram (EEG) on rats and intracranial EEG (iEEG) on patients, we analyze the transient effects of the interictal spikes and waves (SW) on Theta oscillations.Firstly, a method to test the ability of phase synchronization or of phase stability in some frequency band termed as the phase preservation index is developed to measure the SW effects on Theta rhythm before and after SW. The preferred phase bias is simulated based on phase statistics. It is concluded that these two parameters are effective to measure the phase synchronization. It is also resulted that the phase bias is caused by the weak phase difference, whose value is related with the nonlinearity of phase system.Secondly, in order to investigate the effects of the interictal SW on Theta oscillation in hippocampal CA1, dynamics of Theta power and phase stability between the interictal groups (experimental groups) and control groups is compared based on depth EEG data sampled on CA1 channel of 9 adult Wistar rats in exploratory with sniffing. It is found that the interictal SW only in CA1 can disrupt both power dynamics and phase dynamics in Theta oscillations. Meanwhile, preferred Theta phase difference can also support this rule of phase stability. Furthermore, compared to SW epochs with increased Theta power dynamics, SW epochs with decreased Theta power dynamics perform less stable phase dynamics. SW modification has more badly destructive effects on the power dynamics and phase preservation via SW transition in early epileptogenesis.Finally, in order to find the difference of dynamics in Theta oscillations between epileptic rats and patients, the effects of SW on Theta oscillations are investigated based on iEEG data sampled on CA1 channel of 9 epileptic patients in resting. It is found that epileptic patients have strikingly similar rules as rats in both aspects of power dynamics and phase dynamics. However, different epileptogenesis history in epileptic patients might make the dynamics of patients is less obviously than rats. Meanwhile, the phase synchrony and resetting are primarily investigated betewwn CA3 and Entorhinal cortex on epileptic patients.