Predicting the stimulation effectiveness using pre-stimulation neural states via optogenetic activation of the medial septum glutamatergic neurons modulating the hippocampal neural activity.

In this study, we explored the role of pre-stimulation neural states on the effectiveness of optogenetic stimulation. Optogenetic stimulation was applied to the medial septum glutamatergic neurons to modulate the hippocampal neural activity in a rat tetanus toxin seizure model. The hippocampal local field potential was recorded using a multi electrode array in an awake and behaving rat. Optical stimulation with a 465nm light source was applied at 35Hz in a 20 seconds off / 20 seconds on pattern with simultaneous recording from the hippocampus. Both the baseline and the stimulation period recordings were divided into 2 second segments and used for the further analysis. In the first experiment, a support vector machine (SVM) model classified the neural states by using spectral features between 0 and 50Hz. 447 out of 545 segments (82.02%) were correctly labeled as `Baseline' while only 326 out of 544 (59.93%) segments from the stimulation period were correctly labeled as `Stimulation.' As the ratio of mislabels is significantly higher for the stimulation period (chi-squared, p<;0.01), we concluded that the stimulation was not always effective. In the second experiment, an SVM model predicted the stimulation effectiveness using the spectral features of the pre-stimulation segments. The classification result shows that 63.7% of the pre-stimulation segments correctly predicted the stimulation effectiveness. These findings suggest that the prediction of the stimulation effectiveness may improve the stimulation efficacy by implementing a state-based stimulation protocol.