Chunk #226 — VIII. A possible underlying neurobiology: connectivity constellations — B. Quality and/or quantity of connections involved in vulnerabilities
Heritability estimates are available for several of the human phenotypes that are likely to be influenced by the quality and/or quantity of such neuronal connections. Regional brain volumes have been among the most studied using classical twin methods [15]. Some of the best data that is currently available comes from studies of the volumes of the cerebrum, frontal lobe, temporal lobe and hippocampus. These twin studies support heritable interindividual differences in these regions that range from 0.4 to 0.6 [15]. Since the majority of the volumes of the grey matter aspects of these regions is comprised of connection-rich neuropil, it seems highly likely that differences in the quantity of connections provides one substantial source of these heritable interindividual differences.
