New Microscope Offers Unprecedented Deep and Wide-Field Visualization of Brain Activity at Single-Cell Resolution

Conventional multiphoton microscopy, which is fundamental for deep-tissue imaging, faces significant challenges related to imaging depth and field of view, particularly in highly scattering biological tissues such as the brain. To enhance imaging depth while preventing thermal damage, the field of view often diminishes exponentially, complicating the observation of extensive neuronal networks. Now, a groundbreaking microscope has been developed to overcome these limitations by incorporating a range of innovative techniques, enabling researchers to visualize vast areas of the brain at unmatched depths.

A research team at Cornell University (Ithaca, NY, USA) has introduced an advanced imaging technology that offers exceptional deep and wide-field visualization of brain activity at single-cell resolution. This microscope, known as DEEPscope, merges two-photon and three-photon microscopy techniques to capture expansive neural activity and structural details that were previously difficult to access. A key aspect of this advancement is DEEPscope’s adaptive excitation system along with its multi-focus polygon scanning scheme, which facilitates efficient fluorescence generation for large field-of-view imaging. These features enable high-resolution imaging over a 3.23 x 3.23-mm² area with sufficient speed to record neuronal activity in the deepest layers of mouse cortical tissue. Additionally, the capacity for simultaneous two-photon and three-photon imaging increases the system's versatility, enabling detailed investigations of both superficial and deeper brain regions.

Image: A large field-of-view, single-cell-resolution two- and three-photon microscope for deep and wide imaging (Photo courtesy of Mok, A.T., Wang, T., Zhao, S. et al.; doi.org/10.1186/s43593-024-00076-4)

In a study published in the journal eLight, the researchers demonstrated DEEPscope’s ability to image entire cortical columns and subcortical structures with single-cell resolution. They successfully recorded neuronal activity in deep brain regions of transgenic mice, observing more than 4,500 neurons across both shallow and deep cortical layers. Furthermore, DEEPscope facilitated whole-brain imaging in adult zebrafish, capturing structural details at depths exceeding 1 mm and across a field greater than 3 mm—an achievement unprecedented in neuroscience. The techniques demonstrated can be seamlessly integrated into existing multiphoton microscopes, making them accessible for broad applications in neuroscience and other disciplines that require deep-tissue imaging. By addressing previous constraints, DEEPscope establishes a new benchmark for large-field, high-resolution, deep imaging of living tissues, with the potential to enhance understanding of the brain’s complex networks and their significance in health and disease.

“DEEPscope represents a significant advancement in brain imaging technology,” said Aaron Mok, the study's lead author. “For the first time, we can visualize complex neural circuits in living animals at such a large scale and depth, providing insights into brain function and potentially opening new avenues for neurological research.”