FORTUNATO, Santo
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Subsystem organization of axonal connections within and between right and left cerebral cortex and cerebral nuclei (endbrain).Proc. Nat. Acad. Sci. (USA), 115, E6910-E6919, 2018."Significance "The right and left cerebral hemispheres (together forming the endbrain) support cognition and affect, and, structurally, each hemisphere consists of a cortical sheet and set of deep nuclei (often called the basal ganglia). Experimental evidence in the literature identified more than 10,000 axonal macroconnections between the 244 gray matter regions of the endbrain, and the global organizing principles of the network formed by these connections were subjected to multiresolution consensus clustering analysis. The result was a hierarchy of subsystems that has only four components at the top level and 60 components at the bottom level. Furthermore, a region’s status as a connectivity hub in a network is not absolute; it depends on the size and coverage of its anatomical neighborhood. "Abstract "The endbrain (telencephalon) is at the rostral end of the central nervous system and is primarily responsible for supporting cognition and affect. Structurally, it consists of right and left cerebral hemispheres, each parceled into multiple cortical and nuclear gray matter regions. The global network organization of axonal macroconnections between the 244 regions forming the endbrain was analyzed with a multiresolution consensus clustering (MRCC) method that provides a hierarchical description of community clustering (modules or subsystems) within the network. Experimental evidence was collated from the neuroanatomical literature for the existence of 10,002 of a possible 59,292 connections within the network, and they cluster into four top-level subsystems and 60 bottom-level subsystems arranged in a 50-level hierarchy. Two top-level subsystems are bihemispheric: One deals with auditory and visual information, and the other corresponds broadly to the default mode network. The other two top-level subsystems are bilaterally symmetrical, and each deals broadly with somatic and visceral information. Because the entire endbrain connection matrix was assembled from multiple subconnectomes, it was easy to show that the status of a region as a connectivity hub is not absolute but, instead, depends on the size and coverage of its anatomical neighborhood. It was also shown numerically that creating an ultradense connection matrix by converting all “absent” connections to a “very weak” connection weight has virtually no effect on the clustering hierarchy. The next logical step in this project is to complete the forebrain connectome by adding the thalamus and hypothalamus (together, the interbrain) to the endbrain analysis." Subjects: ANATOMY › Neuroanatomy › Cytoarchitecture, COMPUTING/MATHEMATICS in Medicine & Biology, NEUROSCIENCE › Cognitive Neuroscience, NEUROSCIENCE › Computational Neuroscience, NEUROSCIENCE › Computational Neuroscience › Connectomics, PSYCHOLOGY › Cognition |