In recent years, neuroscientists have begun to explore the connection between mind and brain using techniques including functional MRI and magnetoencephalography to show how specific brain regions "light up" during particular activities.
But these techniques have limited spatial resolution and result in images that lack detail. Also, fMRI – which measures the oxygenation of blood rather than the activation of neurons directly – is rather slow.
Injecting neurons with voltage-sensitive dyes that change colour when the brain cells "fire" provides a faster read-out. But the dyes can only be injected into small regions, and the process often damages the tissue.
Now Martin Fischer at Duke University in Durham, North Carolina, US, has developed a new imaging technique. It exploits the fact that the passage of a laser light pulse through neurons is altered when the neurons fire.
By zapping the brain with carefully chosen light pulses, and observing how they are changed by the tissue, it is possible to read out the neuronal activity. Fischer says that this entirely new form of imaging has a spatial resolution on the submicron scale and takes snapshots just milliseconds apart.
However, light will likely only be able to penetrate at best a few millimetres into a brain. Fischer says this is enough to investigate much of the cerebral cortex where the brain's higher function lies. It should also be enough to image entire mouse or rat brains.
Read the full mind-mapping light pulses patent application.
Justin Mullins, New Scientist consultant