The brain is a fascinating organ that regulates movement and most of the hormone-based systems in the body. Much is still unknown about the way the brain functions and how it responds to changes in the environment. Researchers make use of many non-invasive techniques and biomedical innovations to monitor the brain’s role in our movement, emotional patterns, and thoughts. While effective, these techniques are limited in their accuracy when determining brain activity; they give an idea of brain activity rather than discerning the regions active or neurons firing during action. A team of researchers has developed a technique of brain imaging dubbed direct imaging of neural activity (DIANA). This technique seeks to solve the problem of traditional brain imaging, but trouble with reproducing its results calls into question the prospect of its use in medicine and the credibility of those who developed it.
The imaging technique that DIANA hopes to improve is functional magnetic resonance imaging (fMRI), which makes use of the blood oxygenation level-dependent (BOLD) effect. This technique examines the flow of blood that occurs during brain activity. Since different areas of information, blood in the brain tends to flow more toward the parts that are the most active at a given moment in time. fMRIs monitor this change in flow by taking cross-sectional images of the brain at a size determined by the specialists and compiling them to make a full image or video. According to the American Association of Advanced Science, fMRIs are “limited by [their] ability to pinpoint the time and location of specific neuronal activation.” Information in the brain is sent by the millisecond, meaning that blood flow in the brain lags behind the action potential of neurons. The DIANA technique hopes to solve this problem by directly stimulating and imaging the neurons as they fire in order to see brain activity on a smaller scale.
The team responsible for creating the DIANA technique ran their initial trials on anesthetic mice. As reported by McKenzie Prillaman, a writer in the journal Nature, the technique works by “applying minor electric shocks every 200 milliseconds to an anesthetized animal. Between shocks, an MRI scanner collects data from one tiny piece of the brain every 5 milliseconds. After the next shock, another spot is scanned.” The software then stitches the data from the spots together to visualize changes over a 200-millisecond period. It is similar to filming a video pixel by pixel. Prillaman also reports that those responsible claim that this technique could be an improvement over traditional fMRIs because it “could measure the faster-paced signals produced when several neurons change their voltage.” Shifting the focus from blood flow to the change in neuron voltage can allow for a more accurate reading of neural activity that can be used in research moving forward.
The DIANA technique promises to show the accuracy of invasive brain imaging in a non-invasive way. The problem with this technique is that no one outside of the original team has been able to replicate the results of their trials. The team was led by Jang-Yeon Park, an MRI physicist at Sungkyunkwan University in Suwon-si, South Korea. Other researchers have made attempts to replicate the results of DIANA, seeing little to no indication of the signals expected. One team in South Korea altered the original protocol slightly by changing the number of slices taken but found that the more slices they took, the weaker their signals got. This goes against the function of traditional fMRIs, as more slices usually lead to a stronger signal and more information. Another team at Massachusetts Institute of Technology had promising results but realized that they got the same signals when the “electrical-stimulation tool was disconnected, and even when dead rats were being scanned,” reports Prillaman. Neuroscientists continue to cast doubts on this technique, and some have concluded that the signals acquired in the original experiment were not all due to neural activity. Despite this, Park remains hopeful that DIANA will be widely used someday and even goes on to run more trials in both mice and humans. The future of this technique remains uncertain at this time.
