A study published in the Journal of Neuroscience investigated whether brain structures involved in self-processing—how we perceive and think about ourselves—are similar across primates, including humans, chimpanzees, and macaques. Led by Ning Liu from the Institute of Biophysics at the Chinese Academy of Sciences, the research team compared the small-scale structural features and gene expression patterns of these species. They found that humans and macaques share strong similarities in these brain properties, while differences became more apparent when examining large-scale brain connections related to self-processing across all three species. Chimpanzees showed brain patterns that fell between humans and macaques. The study found that the brain system responsible for processing internal bodily signals—such as hunger or pain—was most similar between macaques and chimpanzees. In contrast, the brain system that connects self-related information with the external world, like recognizing one's own actions or emotions in a social context, showed greater similarity between chimpanzees and humans. The system involved in abstract self-related thoughts—like self-reflection or identity—was the most distinct among the three species, suggesting a greater evolutionary divergence in this area. The researchers observed a reorganization of brain regions responsible for processing sensory, motor, and internal information. This reorganization appears to mark a shift from a brain structure focused on bodily processing to one that supports more abstract, mental forms of self-processing. This transition provides insight into how self-related brain architecture has evolved across primates, revealing both shared traits and unique adaptations in different species. Ning Liu plans to integrate these findings with functional and behavioral studies of self-processing to better understand how these brain systems relate to differences in self-awareness and behavior across species. The study, titled "Evolutionary Reorganization of the Self-Processing Network Across Primates," was published in JNeurosci in 2026.