Brain MRIs offer important insight into how our brains work, but they can only produce crude approximations of the areas that are activated by a given stimulus. In order to unravel the minutiae of how neurons communicate and collaborate to form thoughts and feelings, we would need imaging tools with vastly improved resolutions.

Today, far from being able to tackle the 86 billion neurons in the human brain, neuroscientists must settle for studying simple organisms like worms and fish larvae (with neuron counts in the hundreds), relying on slow and cumbersome methods like implanting electrodes into brain tissue to detect electrical signals.

This, however, could soon change. The group of researchers led by Prof. Ed Boyden at MIT has built on previous work to perfect an imaging technique that provides a much fuller picture of the brain's activity. When exposed to red light, a carefully selected fluorescent protein bound to the cellular membrane of neurons reacts to electrical signals by lighting up, to reveal the exact neural path of a thought.