High-speed 3D imaging reveals how seizures move through the brain

Seizures can race through the brain in seconds, making them difficult to capture in detail. To overcome this challenge, researchers have developed a new high-resolution light-sheet imaging system that is fast enough to image seizure propagation in the brain of a larval zebrafish in 3D.

“We developed a light-sheet microscope that allows rapid volumetric imaging with real-time correction of aberrations—imperfections in the way a microscope forms an image,” said research team leader Peter Kner from the University of Georgia. “Most imaging of seizure events in zebrafish has only captured 2D images, but our system allows 3D high-resolution imaging over a larger volume than was previously possible.”

In their article published in the journal Biomedical Optics Express, the researchers show that their new microscopy system can capture volumes up to 499 × 499 × 150 microns³ at a rate of four volumes per second with near-diffraction-limited resolution. They used the system to observe how seizures spread through the nervous system in zebrafish larvae, which are commonly used in neuroscience research.

“The detailed imaging information available from our fast volumetric imaging technique could provide new insights into the mechanisms of seizure formation and propagation, helping guide the development of more effective therapies,” said Kner. “More generally, the approach could improve our understanding of how the brain operates, helping inform the treatment of various brain diseases and disorders.”

Faster 3D imaging

The new work began with a goal of understanding how seizures spread through the brain and how the gene gad1b influences this process. The gad1b gene helps control the neurotransmitter GABA, which is important in brain development and signaling. After using 2D light-sheet microscopy to capture seizure activity in normal zebrafish and zebrafish lacking the gad1b gene, the researchers wanted to visualize how these events unfold throughout the brain in 3D.

Light-sheet microscopy uses a thin sheet of light to illuminate the sample from the side, drastically reducing out-of-focus background light compared with wide-field microscopy. It is also much faster and less phototoxic than techniques like confocal microscopy that also block out-of-focus light.

In previous work, the researchers built a light-sheet microscopy system with a large field of view and sensorless adaptive optics, an approach that calculates optical corrections directly from image quality measurements. However, the system required approximately 1.75 seconds to acquire a single raw volume, which isn’t fast enough to capture rapidly changing brain activity in 3D.

To create a faster imaging system, the researchers used an electrically tunable lens to rapidly move the focal plane through the sample. Although this sped up image acquisition, the researchers also had to develop a method to synchronize the millisecond-scale adaptive optics updates with the microscope’s camera and scanning components. Together, these improvements made it possible to achieve continuous high-speed volumetric imaging without sacrificing image quality.

Watching seizures in the brain

The researchers used their new light-sheet microscope to image the propagation of induced seizures in zebrafish larvae. It acquired 600 volumes continuously over 2.5 minutes—a speed seven times faster than the previous system.

The zebrafish images showed that the seizures originated in the back region of the brain, propagated forward toward the optic tectum—a brain region involved in processing visual information—and then gradually subsided over tens of seconds.

Next, the researchers plan to use the system to image more samples, including zebrafish lacking the gad1b gene. They are also working on a direct wavefront-sensing approach to correct for aberrations in the zebrafish sample, not just the optical system.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

Full profile →

See also  Higher fish intake linked to reduced risk for multiple sclerosis disability worsening

Advertisements

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

Full profile →