Devices detect dopamine as it ripples from one neuron to others nearby.

Tiny brain sensors can detect split-second changes in the levels of a key signalling molecule as it spreads to and influences an array of neurons.

The nervous-system molecule dopamine carries information across the gap between one neuron and another. But it can also seep outside this junction, called a synapse, to communicate with multiple neurons at once. Understanding this process — which is important for dopamine’s role in learning, motivation and motor control — has been difficult because current tools for measuring communication outside neurons are imprecise.

Linda Wilbrecht and Markita Landry at the University of California, Berkeley, and their colleagues sought to design a better brain sensor by wrapping dopamine-sensing molecules around a fluorescent, nanometre-scale tube made of carbon. When added to brain slices, these nanosensors could detect faster dopamine fluctuations in the area surrounding a single synapse than existing gold-standard sensors.

Unlike some currently used methods, the sensors could detect dopamine release in the presence of compounds used in experiments on brain tissue. As a result, they are potentially powerful tools for investigation of dopamine’s many roles in the brain.