Glossary
Gray matter
What is Gray matter?
Gray matter consists of the neuron cell bodies, dendrites, and synapses that form the brain's information-processing tissue. It contrasts with white matter (the myelinated axons that connect regions) and is found in the cerebral cortex, deep nuclei, and cerebellar cortex.
How it works
Structural MRI can estimate gray-matter volume or cortical thickness. Such measures can vary with development, aging and experience, but they do not directly count neurons or provide a simple score of intelligence or brain health.
Applied example
In Erickson and colleagues’ 2011 randomized trial, aerobic training increased anterior hippocampal volume and improved spatial memory in a sample of 120 older adults. This shows that a measured aspect of brain structure can change under particular conditions. It does not tell us that every increase in brain volume is beneficial.
Why it matters
Gray-matter measurements help investigate brain structure and change. Understanding what these measurements reveal about cells and brain function requires evidence beyond the image itself.