MIT scientists have engineered a nano-sized calcium sensor that may eventually shed light on the intricate cell-to-cell communications that make up human thought.

Alan Jasanoff and his team at the Francis Bitter Magnet Lab and McGovern Institute of Brain Research have found that tracking calcium, a key messenger in the brain, may be a more precise way of measuring neural activity, compared with current imaging techniques, such as traditional functional magnetic resonance imaging (fMRI).

Since neurons typically fire on the order of milliseconds, current fMRI techniques provide only a rough estimate of what the brain is doing at any given moment. FMRI scans also have a relatively low spatial resolution, measuring activity in areas of 100 microns, a volume that typically contains 10,000 neurons, each with varying activation patterns.

They are designing a calcium sensor that would be detectable via fMRI. To do this, they combined the sensor with a superparamagnetic iron oxide nanoparticle–essentially, a molecular-sized magnet that can be picked up by fMRI as high-contrast images.