At Hebrew University of Jerusalem, researchers watching a zebrafish closely observed something that had eluded neuroscientists for decades: the brain does not decide to approach another creature in the moment of movement, but seconds before. This insight, published in Nature Communications, comes from an elegant experiment conducted by Dr. Lilah Avitan's laboratory at the Edmond and Lily Safra Center for Brain Sciences (ELSC), where Ph.D. student Imri Lifshitz and the team developed a way to simultaneously record a fish's entire brain activity while watching it react to a swimming neighbor.
The work matters because social interaction lies at the heart of animal and human behavior, yet the neural mechanics of choosing to approach another being remain poorly understood. By using zebrafish as a model organism—creatures whose brains can be observed at single-cell resolution—the researchers could finally see the full picture of how social decisions unfold, moment by moment, as brain and body work in concert.
The setup was ingenious: one fish, head-fixed but with freedom to move its tail, observed a freely swimming companion while two-photon microscopy captured its neural activity in real time. As the researchers tracked both animals' movements—the tail dynamics of the observing fish and the swimming patterns of its companion—they discovered a clear temporal pattern. Several seconds before a fish would swim toward another, coordinated brain activity began shifting across multiple regions. Rather than activating a single "social center," the brain instead orchestrated a distributed, coordinated change: activity rose in the pallium, a higher brain region linked to complex behavior, while activity dropped in other regions simultaneously. This pattern created what researchers describe as a neural "pre-decision state"—a signature that signals an upcoming social action and can be used to predict it before movement actually begins.
What emerged was striking: this pre-decision state was not the same in all fish. Animals showing a stronger brain-wide pattern were more socially engaged overall. In other words, the strength of neural preparation for social interaction directly reflected an individual's social drive. The pallium, the higher brain region that showed activation during this pre-decision state, emerged as particularly important. Its involvement points to a central role in generating and sustaining the motivation to approach others—a finding that could help explain why individuals differ so dramatically in their sociability.
Dr. Avitan summarized the significance plainly: the brain-wide neural signature of social approach emerges before movement begins, predicting not only whether an upcoming action will be social, but also how strongly socially driven the individual is. Because similar brain structures involved in social behavior are conserved across species, from fish to humans, these findings offer a window into how our own brains might generate the drive to connect. The work suggests that social decisions are not spontaneous reactions but carefully orchestrated neural events, prepared in advance, reflecting each individual's unique relationship with others.