GROWTH PATTERNS IN THE DEVELOPING HUMAN BRAIN DETECTED USING CONTINUUM-MECHANICAL TENSOR MAPPING

We report the first, spatially-complex, 4-dimensional quantitative maps of growth patterns in the developing human brain, detected with a tensor mapping strategy that provides growth pattern information with greater spatial detail and sensitivity than previously obtainable in brain imaging studies. By repeatedly scanning children (age: 3-15 yrs.) across multi-year time intervals (up to 4 years), a rostro-caudal wave of growth was detected at the corpus callosum, a fiber system that relays information between brain hemispheres. Children aged 6-15 consistently displayed a localized peak of rapid growth at the callosal isthmus, which innervates temporo-parietal cortices that primarily support associative thinking and language function. Growth rates at the isthmus were attenuated after puberty. An opposite dynamic pattern was found between ages 3 and 6, with most rapid growth in frontal and pre-frontal callosal networks that regulate the planning and organization of new actions. Rates and profiles of tissue growth, elimination, shearing and dilation are visualized in 3 dimensions, revealing the magnitudes, gradients and principal directions of growth throughout the dynamically changing brain. Focal growth of the callosal isthmus and its temporo-parietal projection fields contrasted sharply with a rapid, spatially-localized loss of gray matter in subcortical systems. Dynamic brain maps therefore offer a powerful new means to (1) map growth patterns in an individual child, and (2) gain insight into the complex dynamic processes that affect regional anatomy in the healthy and diseased brain.