In this project, we shine low-power near-infrared laser light at two wavelengths into the heads of human subjects. This light can penetrate far enough to reach the outer cortex of the brain and still diffuse back out of the head. As the content of the blood in the brain changes (due to both volume and oxygenation status), the amount of light exiting the head changes. By measuring these fluctuations in power, we can monitor blood changes in a particular region of the brain. This permits us to detect "activations" in this region, in a manner similar to fMRI.
We have been particularly interested in correcting for hemodynamic trends that are not unique to the brain--i.e. trends that are present additionally in, or only in, the scalp. We detect these using dedicated optical fibers that are placed unusually close to the source fibers on the surface of the head, only 5-6 mm away.
Check out the Publications page to read about our two-layer subtraction method (2005), our experimental demonstration of layer-like hemodynamic trends in human subjects (2008), and our data suggesting that scalp-corrected data provides more reliable estimation of visually-evoked hemodynamic responses (2011). Most recently, we published a paper on ways to obtain a higher percentage of high-quality data runs on infants (2016).