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Bicliques in the Brain: Genetically Driven Wiring of the Connectome
Dániel Barabási
Graduate Student, Biophysics

Unveiling the patterns that characterize the wiring of the connectome is a joint challenge of modern neuroscience and network science. Yet, given the stochastic nature of the current brain wiring models, they are unable to explain the wiring reproducibility that characterizes the C. elegans connectome. Here we start from the hypothesis that the genetic identity of neurons guides synapse and gap junction formation, and show that such genetically driven wiring has testable consequences for the connectome, predicting the existence of densely wired biclique motifs. Guided by this prediction, we identify a family of large, statistically significant biclique subgraphs in the C. elegans and other connectomes, representing local wiring patterns that could not have emerged by chance. The proposed connectome model also predicts that the neurons participating in each biclique must share features of cell identity. In line with this prediction, we find that within each biclique the neurons share statistically significant expression patterns and morphological characteristics, supporting the existence of common genetic factors that drive synapse formation. Finally, we identify  selected genes potentially responsible for the observed local wiring patterns, like the rule of INX-2/INX-3 interaction for gap junction formation. The connectome model offers a self-consistent framework to link the genetics of an organism to the reproducible architecture of its connectome, hence combined with increased coverage of single cell transcriptomics the model could offer experimentally falsifiable predictions on the genetic factors that drive the formation of individual neuronal circuits.

Investigating the Evolution of Social Attention and Long-Term Social Memory in Great Apes
Laura Lewis
Graduate Student, Human Evolutionary Biology

Many primates, including humans, live in large and dynamic communities. They must develop unique social relationships, avoid aggressive interactions, and capitalize on opportunities to scale the dominance hierarchy, learn from others, and successfully reproduce. This type of group-living demands tradeoffs, or biases, in long-term social memory and social attention, defined as directed visual attention toward conspecifics (Watts, 1998; Kano & Call, 2017). Although a growing literature has demonstrated that such biases in social attention and memory exist across many primate species, a key question is how they are shaped by the demands of a species’ socioecology (Parr, 2011; Lonsdorf et al., 2019). Chimpanzees and bonobos provide the ideal model for addressing this question because they live in large multi-female, multi-male communities with fission-fusion grouping patterns and highly differentiated social relationships. My research aims to compare chimpanzee and bonobo socioecology to outline the selective pressures that may have driven the evolution of social attention and social memory in our hominoid lineage. Specifically, I have conducted eye-tracking research with 30 chimps and bonobos in an attempt to answer the following questions: Are chimpanzees and bonobos more attentive to familiar groupmates or unfamiliar strangers? And to what extent do bonobos and chimps remember the faces of previous groupmates? I will present new and preliminary data from a year of research as a visiting scholar at the University of St. Andrews, graciously funded by an MBB Graduate Student Award.