Neural re-use as a fundamental organizational principle of the brain . NEURAL RE-USE IN THE SOCIAL AND EMOTIONAL BRAIN

Presenting evidence from the social brain, we argue that neural re-use is a dynamic, socially organized process that is influenced ontogenetically and evolutionarily by the cultural transmission of mental techniques, values, and modes of thought. Anderson‟s theory should be broadened to accommodate cultural effects on the functioning of architecturally similar neural systems, and the implications of these differences for re-use. Commentary on Anderson Re-use of tissues, organs and systems is a key adaptive strategy in all phyla across evolution and through development (Gould & Vrba, 1982; Andrews, Gangestad & Matthews, 2002). Neural systems are reused in the evolution and development of complex human behaviors, including social emotion and the representation of social status. Research shows (1) evolutionary and developmental reciprocal re-use between social and non-social neural systems; (2) the importance of cultural transmission as a mode for learning evolutionarily and ontogenetically new uses and combinations of neural systems; (3) the possibility that socially mediated re-use may affect the original, primitive function of a neural system, either developmentally or evolutionarily. In short, although Anderson‟s approach maps distinct cognitive functions to unique networks, neural re-use within and between networks is a dynamic process involving culture and sociality. Compassion and admiration: neural re-use between a social and a somatosensory system A growing body of evidence points to developmental and evolutionary re-use between a social and a somatosensory system in the feeling of social emotions. Brain systems involved in the direct sensation of physical pain in the gut and viscera (e.g., during stomach ache), are also involved in the feeling of one‟s own social or psychological pain (Decety & Chaminade, 2003; Eisenberger & Lieberman, 2004; Panksepp, 2005). These systems are also involved in the feeling of late-developing social emotions about another person‟s psychologically or physically painful, or admirable, circumstances (Immordino-Yang, McColl, Damasio & Damasio, 2009) . These systems most notably involve the anterior insula, anterior middle cingulate and ascending somatosensory systems in the dorsal midbrain, most directly associated with regulation of arousal and homeostasis. Comparative social status: neural re-use between a social and a cognitive system The intraparietal sulcus (IPS) is important to representing comparative numerosity, quantity, magnitude, extent, and intensity (Dehaene, 2003; Cohen Kadosh, Lammertyn, & Izard, 2008); it is also involved in representing social status hierarchy (Chiao et al., 2009). Particularly when comparisons are close, neural activations observed within the IPS for numerical and social status comparisons parallel behavioral distance effects in reaction time and error rates, and are thought Commentary on Anderson to reflect a domain-independent spatial representation of magnitude, including the „magnitude‟ of social rank. All animals are responsive to magnitudes, distances, temporal intervals, and intensities (Gallistel, 1993). The neurocognitive systems that support this seem to have been reused in evolution to represent the linear dominance hierarchies that are ubiquitous in both vertebrates and invertebrates. Social dominance hierarchies existed long before the invention of symbols to mediate mathematical calculation, so it is likely that the neural systems modern humans use for analog processing of numerical symbols reflect this phylogenetic history. The social chicken or the useful egg?: learning cognitive skills through cultural