Proper cortical folding is critical to normal brain function, as anomalies in this process are linked to a number of disorders, including schizophrenia, autism, epilepsy, and mental retardation ( Nordahl et al. The models show that the observed deformation after cutting can be caused by more growth in the gray matter than in the white matter, with the estimated tensile stress in the white matter being on the order of 100–1,000 Pa.ĭuring human brain development, the cerebral cortex undergoes substantial folding, which leads to a highly convoluted brain surface. We infer that the cerebral white matter is under considerable tension in the circumferential direction in the coronal cerebral plane, parallel to most of the neural fibers, while the cerebral cortical gray matter is in compression. Cuts into cortical gray matter did not open, but cuts through both layers consistently opened at the point where the cut crossed the white matter. Radial cuts were made either into cortical gray matter, or through the cortex and the underlying white matter tract composed of parallel neural axons. To estimate residual stress in the brain, we performed serial dissection experiments on 500-μm thick coronal slices from fresh adult mouse brains and developed finite element models for these experiments. In addition, knowledge of residual stress is required to fully understand the mechanisms behind traumatic brain injury and changes in mechanical properties due to aging and disease. This finding has important implications for the mechanisms of brain development, as tension in neural axons has been hypothesized to drive cortical folding in the human brain.
This work provides direct evidence that sustained tensile stress exists in white matter of the mature mouse brain.
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