New window system enables long-term studies of brain activity
Bilal Haider studies how several areas of the brain work together for visual perception. This could help researchers understand whether “traffic jams” of neural activity underlie all sorts of visual impairments: from running a red light when visual attention is elsewhere, to light on the affected brain by autism.
To do this kind of work, researchers need a reliable “map” of all visual brain areas with specific coordinates for each unique brain. Drawing the map requires monitoring and recording data from an active and functioning brain, which usually means creating a window in the skull to monitor blood flow activity.
Haider’s team has developed a better approach – a new type of window that is more stable and allows for longer-term studies. Assistant Professor Wallace H. Coulter of the Department of Biomedical Engineering at Georgia Tech and Emory University explains how, in an article published in February in Scientific Reports, a free forum of Nature editing.
To get a clear picture of the brain’s visual network, Haider’s lab uses an established technique called blood flow imaging, which tracks oxygen in the blood, measuring active and inactive areas of a mouse’s brain while the animal visualizes visual stimuli. To capture a strong blood flow signal, researchers typically create a cranial window by thinning the skull or removing a piece of it. These procedures can decrease stability in the awake, throbbing brain – detrimental conditions for delicate electrophysiological measurements performed in the same visual areas after imaging.
“Standard windows give very good images of the vasculature,” Haider said. “But the downside is that if you’re working with an animal learning to perform a sophisticated task that requires weeks of training, and you want to make neural recordings of the brain later, that area has been compromised if the skull is missing or thinned.”
The team’s new cranial window system enables high-quality imaging of blood flow and stable electrical recordings for weeks or even months. The secret is a surgical glue called Vetbond — which contains cyanoacrylate, the same compound found in Krazy Glue — and a tiny glass window.
Basically, a thin layer of glue is applied to the skull with a micropipette and a curved glass coverslip is placed over it. Cyanoacrylate creates a “transparent skull” effect. Haider’s team developed the new window system and then verified the accuracy of the resulting visual brain maps.
“Sometimes the simplest things work. The glue creates a barrier allowing all normal physiological processes to continue, but leaving the bone transparent,” Haider said. “It’s like putting a protector on your smartphone. The protector is on the surface of the glass, but everything underneath remains crystal clear and functional.”
Haider’s approach will help his team achieve their larger goals – to measure the activity of neurons in the brain’s visual pathways and understand how neural traffic jams diminish our visual attention and how these processes may contribute to visual impairments in people with autism. . This is work that is gaining momentum, thanks to recent support from the Simons Foundation Autism Research Initiative.
Haider said a proper study of brain function requires reproducible measurements of neural activity, so he made the new window system available to the public.
“We think it will be a useful tool for other researchers,” he said. “We’ve made the code, all the hardware, all the system specs, everything, totally public so other people can try it out themselves. We designed this to use in our study of the visual brain, but it can potentially be used to study other regions of the brain in a way that allows researchers to do long-term experiments while keeping the brain stable and healthy.”