A neuroanatomical predictor of mirror self-recognition in chimpanzees.
The ability to recognize one's own reflection is shared by humans and only a few other species, including chimpanzees. However, this ability is highly variable across individual chimpanzees. In humans, self-recognition involves a distributed, right-lateralized network including frontal and parietal regions involved in the production and perception of action. The superior longitudinal fasciculus (SLF) is a system of white matter tracts linking these frontal and parietal regions. The current study measured mirror self-recognition (MSR) and SLF anatomy in 60 chimpanzees using diffusion tensor imaging. Successful self-recognition was associated with greater rightward asymmetry in the white matter of SLFII and SLFIII, and in SLFIII's gray matter terminations in Broca's area. We observed a visible progression of SLFIII's prefrontal extension in apes that show negative, ambiguous, and compelling evidence of MSR. Notably, SLFIII's terminations in Broca's area are not right-lateralized or particularly pronounced at the population level in chimpanzees, as they are in humans. Thus, chimpanzees with more human-like behavior show more human-like SLFIII connectivity. These results suggest that self-recognition may have co-emerged with adaptations to frontoparietal circuitry.
Center for Behavioral Neuroscience, ehecht@gsu.edu. Division of Developmental and Cognitive Neuroscience, Yerkes National Primate Research Center, Atlanta, GA, USA. Department of Psychology, Georgia State University, Atlanta, GA, USA. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center. Center for Translational Social Neuroscience. Center for Behavioral Neuroscience, Emory University, Atlanta, GA, USA. Center for Behavioral Neuroscience. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center. The Language Research Center, Georgia State University, Atlanta, GA, USA. Neuroscience Institute, Georgia State University, Atlanta, GA, USA.
