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Figuring out who fired first
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Combining two brain imaging techniques produces a better map of what makes us tick, showing not only the connections between neurons in a network, but the direction in which information flows.
Functional magnetic resonance imaging (fMRI) already provides high-resolution snapshots of brain activity. Since regions that are active at the same time are probably functionally connected, fMRI can be used to build maps of interconnected neurons — but it can’t show which neurons fired first.
A team including researchers from the Technical University of Munich, developed a technique, known as metabolic connectivity mapping (MCM), which relies on the fact that neurons receiving signals use more energy than those sending them. MCM combines data from a PET scan measuring metabolic activity throughout the brain with data about activity from an fMRI, enabling researchers to map which neurons are upstream in a network. These maps may help scientists investigate disorders involving misfiring neural circuits, such as Alzheimer’s disease and major depression.
- Proceedings of the National Academy of Sciences USA 113, 428–433 (2016). doi: 10.1073/pnas.1513752113