Distinct brain-wide neural dynamics predict social approach behavior

Social behavior is essential for animal survival and adaptation, requiring the integration of sensory cues to guide interactions with conspecifics. A key component of social behavior is approach, where animals actively move toward social partners to maintain group cohesion, establish affiliations, and coordinate actions. While a continuous stream of social information is encoded across sensory modalities, it remains unclear whether a distinct neural process underlies social approach. Here, we developed a novel assay in which a head-fixed, tail-free zebrafish interacts with a freely swimming conspecific, enabling precise quantification of social behavior alongside whole-brain functional imaging at cellular resolution. We demonstrate that zebrafish approach behavior is jointly shaped by spatial and temporal information from conspecifics rather than by these features acting independently. Social approach behavior is preceded by distinct brain-wide neural activity patterns emerging seconds before movement onset, characterized by increased activity in a small subset of forebrain neurons and decreased activity in midbrain and hindbrain neuronal populations. These activity patterns reliably predict upcoming approach movements from each of these regions separately. Moreover, the extent to which neural activity distinguishes approach from non-approach movements predicts individual differences in social behavior, directly linking neural dynamics to behavioral variability. Together, our findings reveal a neural mechanism underlying social approach behavior, highlighting how a distributed yet functionally coordinated network facilitates social interaction.