Researchers have reported that they have created a method to combine three brain imaging techniques to capture the location and timing of brain responses to stimuli more accurately. This is the first time the three most widely used technologies have been combined to image brain activity simultaneously. The research is published in the journal Human Brain Mapping.
The new “trimodal” approach combines functional MRI, electroencephalography, and a third technique, EROS, that tracks the activity of neurons near the brain’s surface using near-infrared light.
“We know that fMRI can be very accurate in telling us where things are occurring in the brain, but the signal is quite slow,” Matthew Moore, a postdoctoral researcher, said. The study was first published at the University of Illinois Urbana-Champaign’s Beckman Institute for Advanced Science and Technology. “EEG measures electrical activity in the brain, but it’s not as precise as it can tell us where.
Event-related optical signals, a third method, are similar to fMRI but can be used to measure spatial information. It can also accurately determine the timing of brain reactions, unlike EEG. Moore stated that this technology helps researchers fill in the gaps the two other technologies left. This gives researchers a better understanding of how brain parts are activated and communicated when someone engages in cognitive tasks and is distracted by emotionally challenging information.
Functional MRI records the brain’s signal when a person responds to a stimulus. Moore stated that this signal could be used to determine which brain structures are being activated.
He said the brain responds within hundreds of milliseconds, while blood oxygenation levels can change in seconds. Because of this delay, the fMRI cannot detect changes in brain activity or oxygenation signals that occur faster than two seconds.
Moore stated that EEG helped tell us when things were happening. “But, we collect from sensors placed on the scalp and get a summation activity, so we are blurring across centimeters.
Gabriele Gratton and Monica Fabiani, U. of I. psychology professors, developed the third technique, EROS. The method uses near-infrared light to shine into the brain. It measures changes in the scattering of light, which reflects neural activity. EROS can provide precise information about the brain’s response but can only penetrate a few millimeters beneath the scalp. fMRI, however, can detect brain events deeper within the brain.
It took work to combine the three methods. The researchers stated that there is very little space on the scalp to accommodate different sensors and electrodes. Therefore, EEG and EROS equipment must fit into an fMRI coil. They cannot contain magnetic metals. Researchers found a way for EROS patches to be placed on scalps that could share space with EEG electrodes over a long period. They tried different combinations of these three methods to see how they intertwined and how to interpret the information.
The researchers set the goal for study participants to pick out circles from a series of squares quickly. They also gave them images with negative or neutral content. This was to study the brain’s response when someone tries to focus but is distracted emotionally.
Imaging results showed that different brain regions responded quickly to stimuli. The signals were sent back and forth across other brain regions, including the prefrontal cortices and parietal cortexes. These areas are responsible for maintaining attention and processing distractions. Researchers found this switching occurred on a time scale of hundreds of milliseconds.
Study leader Florin Dolcos from Illinois, who studies cognitive and emotional regulation, stated that switching attention from distraction to getting back to the task is crucial for normal cognitive function.
He said that sometimes people suffering from depression or anxiety have trouble focusing and switching off from their emotions. Better imaging studies will allow for the testing of individuals trained to use specific emotion-regulation strategies to determine if they are improving their cognition. He said we can now see this in real-time, at the mind’s speed.
The trimodal approach will give better answers to questions about brain function and other questions.
“In the past, these technologies were applied to different individuals at different times,” Gratton stated. But measuring these things together is a great way to gain insight.
Fabiani stated, “This new approach could have a profound impact on neuroscience theory in general and human neuroscience.” We don’t need to guess how these signals will align now.
