[What matters more in the white matter: thinking inside of the brain]

The proportion of white matter in the brain has increased during evolution, and white matter comprises approximately half of the human brain. Its macroscopic as well as microscopic structures change during development, aging, and disease progression as well as following physical or mental training. Knowledge about the structural plasticity of the white matter may alter our cortex-oriented view of brain functions and expand our strategies for diagnosis and treatment, including rehabilitation, since the gray and white matter are complementary. Although the presence of white matter lesions is easy to detect with magnetic resonance imaging of the brain, their qualitative differentiation requires vast knowledge about the underlying processes. Examples from multiple ischemic lesions caused by different disease processes affecting the cerebral arteries are presented for comparison. It is worth considering "what matters more in the white matter" by taking into account the basic structures of the brain as well as their plasticity. Such "thinking inside of the brain" may further expand our understanding of the brain to improve our clinical interpretations and treatments.