Circuit dissection and functional validation of a cross-species emotional biomarker

ABSTRACT Emotional responses arise from limbic circuits including the hippocampus and amygdala. In the human brain, beta-frequency communication between these structures correlates with self-reported mood and anxiety. However, both the mechanism and significance of this biomarker as a readout vs. driver of emotional state remain unknown. Here we show that beta-frequency communication between the ventral hippocampus and basolateral amygdala also predicts anxiety-related behavior in mice on both long timescales (∼30 min) and immediately preceding behavioral choices. Genetically encoded voltage indicators reveal that this biomarker reflects synchronization between somatostatin interneurons across both structures. Indeed, synchrony between these neurons dynamically predicts approach vs. avoidance, and optogenetically shifting this synchronization by just 25 msec is sufficient to bidirectionally modulate anxiety-related behaviors. Thus, back-translation establishes a human biomarker as a causal determinant (not just predictor) of emotional state, revealing a novel mechanism whereby interregional synchronization that is frequency-, phase- and cell type-specific controls anxiety processing.