Intrahippocampal and hippocampal-cortical interactions driven by frequency specific optogenetic stimulation

Abstract

Previous studies suggested that the intrahippocampal interactions may be governed by gamma oscillations, while hippocampal-cortical interactions might be directed by low frequency oscillation and/or sharp wave-ripple. However, exactly how different frequency contributes to large-scale intrahippocampal and hippocampal-cortical interactions remains largely unknown. In this study, optogenetic functional MRI was applied to investigate the frequency-dependent hippocampal network activity. Large-scale hippocampal and cortical activations were found during 40Hz and 1Hz stimulation, respectively. This is also the first study demonstrating large-scale and widespread hippocampal-cortical activity by driving CaMKIIa-positive cells in the dorsal hippocampus. This widespread hippocampal-cortical activity suggests that the generation of low frequency oscillation in the dorsal hippocampus can modulate cortical activity.