Pre-Ictal Entropy Analysis of Microwire Data from an Animal Model of Limbic Epilepsy

Epilepsy is a common neurological disorder that can have damaging effects in the brain including over 50% loss of neuronal activity in the hippocampal regions of the CA1 and CA3. The pre-ictal period was studied in an animal model of limbic epilepsy using Shannon entropy and correlation analysis. The primary aim was to uncover underlying relative changes in signals between the Dentate Gyrus and CA1 areas of the bilateral hippocampus. Preliminary entropy analysis results included dynamical changes between channels in the Dentate Gyrus and channels in the CA1 region at and around the time of the seizure. Epilepsy affects 3-5% of the population worldwide. Epilepsy is a neurological disorder characterized by recurrent and unprovoked seizures. An individual loses awareness when experiencing a complex partial seizure due to the spread of the seizure through both temporal lobes and subsequently impairing memory. (1) Of all cases, approximately 60% respond favorably to anti-epileptic drugs. (2) Regardless of age, sex or race, the harmful effects of limbic Epilepsy can be caused by past infections, vascular malformations, hamartomas and gliomas. Head trauma in the form of hemorrhaging or contusion in the brain often leads to the development of limbic Epilepsy after a number of months to years. This span of time is known as a latent period when cellular and network changes are thought to occur precipitating the onset of seizures. In epileptogenesis over 50% of the neurons in the hippocampal regions of the CA1 and CA3 are lost. Neuronal loss also occurs with the granule cells in the Dentate Gyrus; accompanying these changes is a loss of inhibitory neurons, excitatory neurons and excitatory axonal sprouting. (1) The Chronic Limbic Epilepsy rat model imitates human limbic epilepsy with the initial insult to the brain quiescent period and resultant seizures later in life. The manner in which these seizures develop is thought to be a result of structural changes in the brain such as the strengthening of excitatory networks, loss of inhibitory neurons or suppression of GABA receptors. (3) Since little is known about the time period over which the changes occur, it is proposed that detectable changes occur gradually within the brain over the latent period eventually causing the later hypersynchronous seizure activity. The link between the nature of the pre-ictal period and the electrical changes manifested in the brain are not well characterized. The abnormal mode of communication, a characteristic of seizures, is demonstrated by large- amplitude wave discharges occurring over a large hemisphere of the brain. The preictal period in an animal model of limbic epilepsy is studied using Shannon entropy measurements. The goal of this research is to characterize underlying changes in signals between the Dentate Gyrus and CA1 areas of the bilateral hippocampus.