A new grant to Professor Eyal Gruntman from the Canadian Foundation for Innovation (CFI) will purchase a light-sheet microscope to speed up his experiments and greatly increase the area of the brain he can survey.
For his experiments at UofT Scarborough, fruit flies are suspended in a circular LED visual arena that presents visual stimuli to the flies and records their responses. The amplitude of wingbeats is measured from their shadows and that is how their turning responses are deduced.
“One test we can use relies on the reverse Phi illusion,” Gruntman explains. “If you show a bar of light moving in one direction but you rapidly flip the contrast, flies (and humans) actually perceive the bar as moving in the opposite direction. The behaviour of the fly will reflect whether it is perceiving the illusion.”
Gruntman can record the activity of the visual centres of the fly brain to assess how the behaviour of the fly is reflected in neural activity. His previous work showed that neurons responsible for computing motion change their directional preference when presented with a reverse phi stimulus.
The CFI-funded light sheet microscope (LSM) will be combined with expansion microscopy to provide unprecedented levels of detail. Expansion microscopy increases the resolution of images by physically expanding the sample and revealing details that would otherwise be below the diffraction limit of light.
Gruntman will assess how circuit function is maintained despite dynamic changes to neuronal connectivity. “We want to look downstream of motion-computing neurons,” Gruntman explains.
“In the fly, just like in mammals, there’s this split where motion is computed separately for bright and dark objects, but then it’s reintegrated at a particular neuropil, a bundle of nerve fibres. Neurons in the Bright and Dark pathways change their morphology throughout the day, the LSM will allow us to follow this process throughout the circuit and see how information is actually being reintegrated.”
The Gruntman lab currently has two master’s students and several undergrads currently in the lab. He is seeking additional graduate students for imaging work using the light sheet microscope made possible by CFI funding.
Congratulations, Professor Gruntman!