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A light-sensitive receptor protein expressed in neurons deep in the mouse brain has been shown to be stimulated by violet light, and to activate a pathway that reduces heat production in brown fat. Opsin 5 photoreceptors in the hypothalamus control thermoregulation.

The theory that haemoglobin evolved to carry oxygen around the body may need a rethink in light of another way in which molecules related to nitric oxide, released from haemoglobin, help the brain control respiration.

Restoring voluntary actions to paralysed patients is an ambition of neural-interface research. A study shows that people with tetraplegia can use brain control of a robotic arm to reach and grasp objects. See Letter p.372 John Donoghue and colleagues have previously demonstrated that people with tetraplegia can learn to use neural signals from the motor cortex to control a computer cursor. Work from another lab has also shown that monkeys can learn to use such signals to feed themselves with a robotic arm. Now, Donoghue and colleagues have advanced the technology to a level at which two people with long-standing paralysis — a 58-year-old woman and a 66-year-old man — are able to use a neural interface to direct a robotic arm to reach for and grasp objects. One subject was able to learn to pick up and drink from a bottle using a device implanted 5 years earlier, demonstrating not only that subjects can use the brain–machine interface, but also that it has potential longevity.

Paralysed patients would benefit if their thoughts could become everyday actions. The demonstration that monkeys can use brain activity for precise control of an arm-like robot is a step towards that end.