Carnegie Mellon University

Functional Brain Imaging with EEG and fNIRS

Your brain is a network! Just like the computer network that you are currently enjoying, you can think of different parts of the brain as a group of computers - they have their own jobs, they are connected, both physically and functionally, and they work together to keep the world’s most elegant machine active. Yet unfortunately, we are not yet able to fully appreciate how the connectivity works, especially in terms of how neuronal changes are related with vascular changes, or in a more formal terminology, neuro-vascular coupling.
By taking advantage of simultaneous multimodal measurement (namely electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS)), we are now able to explore these questions:
Are neural activities correlated with vascular changes?
Are the correlated changes co-located?
Are the correlations broad band, or frequency specific?
What’s the time lag between those changes?
During a task, does functional connectivity change?
Do connectivity changes observed in two modalities agree with each other?

Of course, you can use your illusion to ask even more questions. You may ask why would we choose fNIRS over more widely use fMRI for vascular measurement. The short answer is, because its cheaper, smaller, faster, and richer in information. Admittedly, fMRI has far better spatial resolution, but the poor temporal resolution (typically on the order of seconds) won’t allow it to capture fast changes. fNIRS on the other hand, provides significantly higher temporal resolution (on the order of 10 milliseconds!), and the really cool part is, it can give us concentration changes of both oxyhemoglobin and deoxyhemoglobin.
In figure, functional connectivity is demonstrated, where red color implies high correlation and blue implies low. We put the “seed“ point at the front-left part of the head, and checked correlation between this “seed” region and all other regions. As you probably have guessed, the seed is highly correlated with nearby regions, as well as the contralateral region, due to symmetry of the brain.

People involved in this project: