Scientists have created the first map showing mitochondria throughout an entire human brain, Nature News reports (open copy).

Mitochondria generate the energy that cells need to work. The new map reveals that mitochondria differ across the brain. Their type and how many there are varies between brain parts. For example, older brain regions have fewer mitochondria. Newer brain regions have more. The brain uses about 20% of the body’s total energy.

To study mitochondria, the scientists divided a brain slice from a donor slice into 703 tiny cubes. Each cube measured 3 millimeters per side. This size is similar to units in 3D brain images. Handling so many small samples was challenging. The investigators used special biochemical and molecular methods to study the cubes. They counted the mitochondria in each cube. They also measured how well some mitochondria produced energy.

Mapping Mitochondria Across the Brain

A paper published in Nature describes the methods and results of this study. See also this summary.

The scientists developed a computer model. This model predicted mitochondria numbers and types across the whole brain. They used brain imaging data and data from the brain cubes to build the model. Then they checked their model using other brain samples.

The model accurately predicted the mitochondria in those samples. The results showed mitochondrial differences between brain areas. Grey matter, which consists of neuron cell bodies, has over 50% more mitochondria than white matter. White matter mainly contains the long branches of neurons. Grey matter mitochondria also generate energy more efficiently. This efficiency was highest in the brain cortex. The cortex is the brain’s wrinkled outer layer. It handles complex functions.

Evidence suggests mitochondria change early in some diseases. These include psychiatric conditions and age-related brain disorders.

The researchers plan to map brain regions in 500 human brains. This will allow comparisons between individuals. They will compare people with and without brain disorders. These include neurological, psychiatric, and neurodegenerative disorders.

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