Optogenetic-silencing mouse fMRI reveals spontaneous neural activity propagating through polysynaptic structural connectivity

Motivation: Resting-state functional connectivity is believed to reflect polysynaptic connectivity, but whether spontaneous neural interactions involve polysynaptic connectivity remains unclear. Goal(s): This study investigates the role of polysynaptic connectivity in propagating spontaneous neural activity. Approach: We mapped evoked and spontaneous neural interactions using mouse fMRI with optogenetic activation or silencing of neural activity and compared them with polysynaptic structural connectivity. Results: Spontaneous activity propagated through polysynaptic pathways, while evoked activity was confined to monosynaptic connectivity. This suggests that polysynaptic connectivity is crucial in shaping spontaneous neural interactions underlying functional connectivity. Impact: This study aimed to elucidate the relationship between resting-state functional connectivity and causal neural interactions assessed by optogenetic fMRI, with a specific focus on the role of polysynaptic structural pathways.