Study On The Relationship Between Spatial Memory And Electroencephalogram Rhythm In The Temporal Lobe Epilepsy Rats

Temporal lobe epilepsy(TLE)patients usually performe severe spatial memory deficiency.Recent studies found that hippocampus theta rhythm and sharp waveripple(SPW-R)could be spatial memory biomark.Physiological ripple is highly instable as its hysynchronous oscillation characteristic and is easily influenced by epilepsy then becomes pathological fast ripple,which may cause cognitive impairment.The study on the mechanism of TLE spatial memory deficicy needs more detail studies to expose the relationship between spatial memory deficiency and abnormal EEG.We established a pilocarpine TLE animal model,then performed behavioral and neurophysiological recordings in TLE rat with intracranial depth electrodes in hippocampus CA1,entorhinal cortex(EC)and prefrontal lobe cortex(PFC).Then,we collected rat’s theta rhythm(4~12Hz),ripple(140~250Hz)and fast ripple(250~500Hz)during exploration and slow wave sleep(SWS),which were properly analyzed to expose the relationship between epileptic spatial memory impairment and abnormal EEG.The main results are as follows:1.Healthy rats detected object position change and enhanced exploration during the spatial explore progress,meanwhile CA1 and EC performed a stable theta rhythm,coherence values between CA1 and EC,PFC and EC were enhanced during theta rhythm;the duration of SWS and explore time showed a linear correlation,rats could remember the object position changement and showed impotent curiosity after a period of slow wave sleep,hippocampus CA1 SPW-R incidence and peak frequency were improved after training,which all supported that healthy rats owned normal spatial memory.2.After status epilepticus,TLE rats CA1 and entorhinal cortex ripple peak frequency were elevated in baseline slow wave sleep state,CA1 ripple peak frequency changed its extent with epilepsy development,which accounted for the electrophysiological characteristics change of ripple in TLE rats.3.TLE rats cannot observe object position change and showed unchanged explore time during exploration,its CA1 and EC showed a decreased-frequency theta rhythm,coherence value between PFC and EC was not improved during theta thythm;the curiosity of TLE rats spatial exploration did’t change after SWS process,hippocampal CA1 SPW-R incidence and peak frequency were not changed after training,but EC ripple incidence and CA1,EC fast ripple incidence were improved after traing,which accounted for the relationship between spatial memory demage and EEG rhythm alteration.In conclusion,our experiment found that TLE rat performed an impaired spatial memory ability,high frequency oscillation changed its extent with epilepsy development,which provided a robust evidence for cognitive impairment of epilepsy.