High-throughput sequencing of macaque basolateral amygdala projections reveals dissociable connectional motifs with...

The basolateral amygdala (BLA) projects widely across the macaque frontal cortex^1-4, and amygdalo-frontal projections are critical for optimal emotional responding⁵ and decision-making⁶. Yet, little is known about the single-neuron architecture of these projections: namely, whether single BLA neurons project to multiple parts of the frontal cortex. Here, we use MAPseq⁷ to determine the projection patterns of over 3000 macaque BLA neurons. We found that one-third of BLA neurons have two or more distinct targets in parts of frontal cortex and of subcortical structures. Further, we reveal non-random structure within these branching patterns such that neurons with four targets are more frequently observed than those with two or three, indicative of widespread networks. Consequently, these multi-target single neurons form distinct networks within medial and ventral frontal cortex consistent with their known functions in regulating mood and decision-making. Additionally, we show that branching patterns of single neurons shape functional networks in the brain as assessed by fMRI-based functional connectivity. These results provide a neuroanatomical basis for the role of the BLA in coordinating brain-wide responses to valent stimuli⁸ and highlight the importance of high-resolution neuroanatomical data for understanding functional networks in the brain.