Dr. Scott Cruikshank
Research Associate Professor of Neuroscience
Brown University, Rhode Island, USA
Dr. Cruikshank and colleagues are interested in information processing in the brain, focusing on circuits linking the brain’s neocortex and thalamus. These circuits are critical to sensation, perception and learning. Using optogenetic probes, fluorescent and bioluminescent proteins and electrical recording, they can activate and or inhibit particular pathways and measure changes in downstream processing.
The group often image axon terminals that contain channelrhodopsin and other opsins tagged with fluorescent proteins. These terminals are fine structures and are sometimes only weakly fluorescent, causing problems with signal to noise in the resulting images.
Dr. Cruikshank told us, “We have typically used a fast sCMOS camera that can acquire images at 100 Hz (full frame) but the quantum efficiency of that camera is just 60%, and the signal to noise ratio is generally low at fast frame rates.”
Common solutions to weak signals can include illuminating with higher intensities or for a longer duration, but this can excessively activate the channelrhodopsins used to control the neuronal excitability. Uncontrolled activation of the channelrhodopsins can lead to prolonged changes in neuronal behavior, confounding the results of the experiments. On the other hand, lowering the illumination intensities and/or exposure times enough to minimize channelrhodopsin activation can degrade the ability to detect and image labeled nerve terminals.
Using the Prime BSI to image weakly illuminated and sparsely labeled fluorescent neurons, we are able to avoid uncontrolled activation of channelrhodopsin while imaging the signal in axon terminals using short exposure times