The Vaziri and Zimmer research groups in Vienna, Austria, have demonstrated a high-speed imaging technique that allows neuronal activity across the entirety of a roundworm’s (Caenorhabditis elegans) brain to be recorded simultaneously. The research was described in a paper published in journal Nature Methods.
The groups' success in being the first to implement brain-wide imaging was thanks to a novel calcium indicator and the Andor Neo 5.5 megapixel sCMOS camera, according to Vaziri group leader Professor Alipasha Vaziri.
Vaziri explained that the camera allowed the team to image a worm’s brain four to six times a second using wide-field temporal focusing two photon microscopy. The calcium indicator increased a neurons' fluorescence to visualise its activity and permits unambiguous discrimination of individual neurons within the densely packed head ganglia.
‘The value of this work to the neuroscience community is evident in the attention it attracted online, ranking second overall for Nature Methods," says Orla Hanrahan of Andor. ‘Because their imaging methodology can also be applied straightforwardly to other organisms, or more general imaging tasks, and since their novel calcium reporter is a very powerful tool that can be used by all neuroscientists working on C. elegans, their technique has already had a large impact. If a lab-on-a-chip device is deployed for stimulus delivery in the future, this method provides an enabling platform for establishing functional maps of neuronal networks.’
WF-TeFo microscopy allowed users to independently control the axial and lateral confinement of the excitation area while taking advantage of the high depth penetration and low scattering properties of two-photon excitation.
For volumetric imaging, the group scanned an excitation area of roughly 60μm in diameter with an axial confinement of around 1.9μm in the axial direction to speed up the volume acquisition time. A volume acquisition rate approaching 13Hz was achievable but imaging was performed at speeds of 4-6Hz, corresponding to 5.6 megavoxels per second, achieving a lateral spatial resolution of 0.285μm.
Dr Manuel Zimmer explained the choice of camera: ‘The Andor Neo camera was one of the only two sCMOS cameras then available and our demo-trial convinced us that it provided the fastest speed while retaining high sensitivity and a wide dynamic range.’
