The role of long-range connections on the specificity of the macaque interareal cortical network

• DOI: 10.1073/pnas.1218972110
• Publication Date: 2013-03-12T01:09:22Z
• Authors: Nikola T. Markov; Maria Ercsey-Ravasz; Camille Lamy; Ana Rita Ribeiro ...; Loïc Magrou; Pierre Misery; Pascale Giroud; Pascal Barone; Colette Dehay; Zoltán Toroczkai; Kenneth Knoblauch; David C. Van Essen; Henry Kennedy
• Keywords: Cerebral Cortex; Brain Mapping; anatomy; Databases, Factual; 03 medical and health sciences; 0302 clinical medicine; neocortex; Animals; Macaca; [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]; [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]; monkey; Nerve Net

We investigated the influence of interareal distance on connectivity patterns in a database obtained from the injection of retrograde tracers in 29 areas distributed over six regions (occipital, temporal, parietal, frontal, prefrontal, and limbic). One-third of the 1,615 pathways projecting to the 29 target areas were reported only recently and deemed new-found projections (NFPs). NFPs are predominantly long-range, low-weight connections. A minimum dominating set analysis (a graph theoretic measure) shows that NFPs play a major role in globalizing input to small groups of areas. Randomization tests show that ( i ) NFPs make important contributions to the specificity of the connectivity profile of individual cortical areas, and ( ii ) NFPs share key properties with known connections at the same distance. We developed a similarity index, which shows that intraregion similarity is high, whereas the interregion similarity declines with distance. For area pairs, there is a steep decline with distance in the similarity and probability of being connected. Nevertheless, the present findings reveal an unexpected binary specificity despite the high density (66%) of the cortical graph. This specificity is made possible because connections are largely concentrated over short distances. These findings emphasize the importance of long-distance connections in the connectivity profile of an area. We demonstrate that long-distance connections are particularly prevalent for prefrontal areas, where they may play a prominent role in large-scale communication and information integration.