The statement “all white matter” refers to the distribution of a substance or structure throughout all regions of the white matter in the central nervous system. White matter is the tissue in the brain and spinal cord that is composed mainly of myelinated axons, which are long fiber-like structures that transmit electrical signals between different regions of the central nervous system.

The distribution of various substances, including neurotransmitters, receptors, and proteins, can vary across different regions of the white matter. However, substances that are distributed “throughout all white matter” would be present in a relatively homogeneous and uniform manner across all regions of the white matter.

For example, myelin, the fatty substance that forms the insulation around axons, is distributed throughout all regions of the white matter, where it plays a critical role in enabling fast and efficient signal transmission. Similarly, oligodendrocytes, the glial cells responsible for producing myelin in the central nervous system, are also distributed throughout all regions of the white matter.

Understanding the distribution of substances and structures throughout the white matter is important for understanding the complex processes that occur in the central nervous system, including sensory processing, motor control, and higher cognitive functions. Deviations from normal distribution patterns can also provide important insights into the underlying pathology of neurological disorders, such as demyelinating diseases like multiple sclerosis.