DIMENSIONALITY ALTERATIONS OF THE HIPPOCAMPAL ELECTROENCEPHALOGRAPHICACTIVITY FOLLOWING THE INDUCTION OF LONG-TERM POTENTIATION IN RATS

In the present in vivo experimental study the complexity alterations o f the hippocampal electroencephalographic (EEG) activity were investig ated prior and during the maintenance phase of long-term potentiation (LTP), using analytical methods based on the recent concepts of determ inistic chaos. LTP was induced in the hippocampal dentate hilus after stimulation of the medial perforant path of the rat's brain. During th e experimental procedure hippocampal EEG epochs were recorded prior an d after the induction of LTP. Dimensionality computations performed on these epochs showed a maintained relative reduction in the correlatio n dimension during the maintenance phase of LTP. This result might sug gest that different functional states of the brain are governed by dif ferent degrees of complexity and that the altered efficacy in the info rmation process, as it is achieved by the induction of LTP, modifies t he spontaneous EEG activity of the potentiated hippocampal area in a p lastic manner.