Deriving causal relationships in resting-state functional connectivity using SSFO-based optogenetic fMRI.

Area of Science:

• Neuroscience
• Systems Neuroscience
• Brain Network Analysis

Background:

• Brain networks are characterized by functional interconnections between regions.
• Understanding causal relationships within brain-wide functional connectivity is crucial but challenging.
• Existing methods struggle to infer directional information in complex neural circuits.

Purpose of the Study:

• To investigate the feasibility of using Stimulating and Silencing Fluorescent Opsins (SSFO)-based optogenetic functional magnetic resonance imaging (fMRI) for inferring causal relationships in brain networks.
• To examine how local increases in neuronal excitability affect brain-wide neural activity and resting-state functional connectivity (RSFC).

Main Methods:

• Combined SSFO-based optogenetics with fMRI in a resting-state rodent model.
• Localized increase in excitability in the dentate gyrus (DG) using SSFO activation.
• Applied Pearson's correlation and partial correlation analyses within a graphic model to derive directional information from RSFC modulations.

Main Results:

• SSFO activation in the DG led to significant changes in activity and connectivity in associated brain regions, notably the medial prefrontal cortex.
• The causal inference method achieved an 84%-100% accuracy rate when compared to anatomical tracing data.
• Demonstrated a link between local region activity modulation and brain-wide RSFC changes.

Conclusions:

• Established a novel system for investigating the relationship between local brain region activity and RSFC modulation.
• Provided a robust method for analyzing the underlying causal relationships within brain networks.
• Highlights the potential of optogenetic fMRI for mapping directed functional connectivity.