http://www.pnas.org/content/early/2013/09/25/1306095110.abstract
The “midbrain periaqueductal gray region,” or PAG, is extraordinarily difficult to investigate in humans because of its size and intricate structure. Northeastern University researcher Ajay Satpute is uses state-of-the art imaging to capture this complex neural activity. His technique increases the spatial resoluion of fMRI. As fMRI lacks temporal resolution, there is much room for improvement.
Satpute’s goal is to help scientists explore the grounds of human emotion. “The PAG’s functional properties occur at such small spatial scales that we need to capture its activity at very high resolution in order to understand it,” he explained.
Until recently, neuroimaging studies have been done with fMRI, providing data for understanding how the different areas respond to different stimuli. When those areas become sufficiently small and complicated, their resolution falls short. In the case of the tiny PAG, this problem is paramount because the PAG wraps around a hollow core, or “aqueduct,” containing cerebrospinal fluid, Satpute said. Traditional fMRI instruments cannot distinguish neural activity occurring in the PAG from that occurring in the CS fluid. Even more difficult is identifying where within the PAG itself specific responses originate.
Collaborating with researchers at Massachusetts General Hospital, Satpute used a seven Tesla magnet fMRI. Coupled with manual data analyses, he was able to resolve activity in sub-regions of the PAG with more precision than ever before. The research team showed 11 human subjects images of burn victims, gory injuries, and other content related to threat, harm, and loss while keeping tabs on the PAG’s activity. The subjects also viewed neutral images. The researchers compared results between the two scenarios. The proof-of-concept study showed emotion-related activity concentrated in particular areas of the PAG. While similar results have been demonstrated in animal models, nothing like it had previously been shown in human brains.
Using this methodology, the researchers said they would not only gain a better understanding of the PAG but also be able to investigate a range of brain-related research questions beyond this particular structure.
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