Optical reporters of neural activity have improved dramatically over the past decade. Recent developments in optical imaging approaches have unlocked the power of these indicators and can now provide real-time read-outs from large populations of brain cells in a wide range of living organisms. We have recently contributed two imaging methods to this field, swept confocally aligned planar excitation (SCAPE) microscopy and wide field optical mapping (WFOM).
SCAPE microscopy is a high-speed light-sheet imaging method that permits cellular-level 3D imaging at over 100 volumes per second. Combining low phototoxicity benefits with a simple, single stationary objective lens, SCAPE permits high-speed microscopy that is well-suited to the study of behaving small model organisms such as C. elegans worms, zebrafish larvae and adult and larval Drosophila. The method can also be applied to high-speed, volumetric functional imaging the intact, living rodent brain as well as enabling high-throughput structural imaging of large cleared of expanded tissues. In addition to focusing on key neuroscience applications, we have also made many technological advances that have dramatically improved SCAPE’s resolution and field of view. We are also developing two-photon, meso-scale and high-resolution versions of SCAPE.
WFOM is an LED-based imaging technique that uses the combination of wide-field fluorescence and absorption measurements over the entire dorsal surface of the mouse cortex, through thinned skull. Although not seeking to achieve single-cell resolution or depth-resolved imaging, WFOM can generate real-time images of neural activity across much of the mouse cortex, with simultaneous mapping of hemodynamic changes which permit both correction of fluorescence for absorption artefacts, and analysis of real-time neurovascular coupling. The power of this simple technique is the ease with which data can be acquired longitudinally in awake, head-fixed mice during stimuli or tasks, while behaving spontaneously, under perturbations or interventions and during disease progression. Comprehensive behavioral monitoring can be acquired in parallel.
Both of these techniques have the ability to capture real-time activity across large areas of the brain, in the context of increasingly natural behaviors. Without needing averaging over multiple repeated trials or tasks, this data permits the application of ‘big-data’ techniques to understand network-wide neural representations of complex and spontaneous behaviors, and could potentially provide new insights into the brain’s representation of internal state.