Predictions in Absence Epilepsy with the use of Computer Models of Neuronal Networks

A computer model of a thalamic network was used in order to understand the rhythmic activity that characterizes absence epilepsy. The model was constructed using a Hodgkin Huxley framework. Results from the model confirm the hypothesis that an isolated augmentation of the maximum conductance of the low threshold calcium current (I_T) in the reticular thalamic nucleus may be conducive to the occurrence of autorhythmicity and hence epilepsy. The model predicts that higher values of this I_T can cause the transition of the network to an intermittent state. This intermittency increased monotonically with the increase of I_T in the reticular nucleus. The model was also used to investigate electrophysiological methods of bringing about a transition of the network to a subthreshold state. Methods that were successful at bringing about a phase shift that resulted in the reticular thalamic neurons firing before the thalamocortical neurons were found to lead to subthreshold activity in the network. This sort of phase shift was attained either by the application of periodic excitatory pulses to the reticular thalamic neurons or the application of a constant hyperpolarization to the thalamocortical neuron.