Modulation of local field potentials by high-frequency stimulation of afferent axons in the hippocampal CA1 region

Modulation of the rhythmic activity of local field potentials (LFP) in neuronal networks could be a mechanism of deep brain stimulation (DBS). However, exact changes of LFP during the periods of high-frequency stimulation (HFS) of DBS are unclear because of the interference of dense stimulation artifacts with high amplitudes. In the present study, we investigated LFP changes induced by HFS of afferent axons in the hippocampal CA1 region of urethane-anesthetized rats by using a proper algorithm of artifact removal. Afterward, the LFP changes in the frequency bands of delta, theta, alpha, beta and gamma rhythms were studied by power spectrum analysis and coherence analysis for the recorded signals collected in the pyramidal layer and in the stratum radiatum of CA1 region before, during and after 1-min long 100 and 200 Hz HFS. Results showed that the power of LFP rhythms in higher-frequency band (gamma rhythm) increased in the pyramidal layer and the power of LFP rhythms in lower-frequency bands theta, alpha and beta rhythms) decreased in the stratum radiatum during HFS. The synchronization of theta rhythm decreased and the synchronization of gamma rhythm increased during HFS in the stratum radiatum. These results suggest that axonal HFS could modulate LFP rhythms in the downstream brain areas with a plausible underlying mechanism of partial axonal blockage induced by HFS. The study provides new evidence to support the mechanism of DBS modulating rhythmic activity of neuronal populations.