Researchers have used a genetically altered virus to map the neural inputs that project into regions of the brain that control food intake. According to the scientists, these experiments represent a step in understanding the neural circuitry that executes decisions about whether or not to eat.

The virus, which travels upstream from the site of infection, jumping from neuron to neuron, was engineered to carry a gene for green fluorescent protein. The presence of the fluorescent protein enabled the scientists to trace the path of the virus as it moved through the brain.