Looking at the brain through the skull

This illustration shows how carbon nanotubes, once injected into the subject, can be fluoresced using near-infrared light in order to visualize the brain vasculature and track cerebral blood flow. Credit: Dai Lab

A significant part of the progress we have seen in the understanding of the brain (which is far by being understood..) derives from technology advances in looking inside a "working" brain. PET and fMRI have allowed the identification of areas in the brain that are involved in the processing of stimuli. This in turns allowed scientists to work out a mapping of brain areas to function (a first mapping goes back to the first part of last century and was based on injuries and resulting disabilities).

The more we can look at the living brain the more we can learn. Now, researchers at Stanford have discovered a way to "look" inside the skull to watch the brain.

To understand what they did we need to understand that when we say that an object is transparent to light we mean that it is transparent to the light "we" see (the visible spectrum), and that is a very small part of the electromagnetic spectrum. Objects may be transparent to wavelengths that our eyes cannot see but that can be seen by instruments.

Our skull (and the skin covering it) is not transparent to the visible spectrum but it is transparent to other wavelength, like light at 808nm (infrared) and at 1,300-1,400nm. The researchers at Stanford discovered that nanotubes illuminated at 808nm fluoresce at the 1,300-1,400nm and this particular wavelength not only goes through the skull but it is not scattered, hence it can provide an accurate image.

The procedure has been experimented on mice. They have been injected with a solution of nanotubes, their head illuminated by a laser at 808nm and they have been able to record the image of the brain capillaries at a resolution of a few microns up to a depth of 3 mm under the meninges. This is by far a greater resolution and it will allow neuroscientists to harvest more information on the way the brain works.

Author - Roberto Saracco

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