Ultra-Widefield All-Optical Neurophysiology in Tissue

Summary

Date: 
October 4, 2017 - 1:00pm
Location: 
Northwest Building, Room 243
About the Speaker
Name: 
Samouil Farhi
Speaker Title: 
PhD Candidate, Cohen Lab

All-optical approaches for simultaneous recording and perturbation of neuronal activity could enable functional mapping of brain circuits. Spectral overlap of actuators and reporters presents a challenge for their simultaneous use, while optical scattering and out-of-focus fluorescence are challenges for imaging densely labeled samples over large fields of view. To overcome the first challenge, we coupled a red-shifted calcium indicator with a spectrally-orthogonal blue-shifted channelrhodopsin, enabling single-photon all-optical neurophysiology. To overcome the second challenge, we designed an ultra-widefield optical system to image a 5 mm field of view with single-cell lateral resolution. A digital micromirror device illuminates neighboring sample locations with temporally orthogonal light sequences based on Hadamard matrices, enabling computational rejection of scattering and out-of-focus light. By uniting these molecular and optical tools we measure functional properties of thousands of neurons in parallel in acute slices. We map the effects of anti-epileptic drugs on excitability throughout the cortex and striatum. We also map the post-synaptic responses driven by layer 5 cortical neurons in cortex and striatum. These results demonstrate a robust tool for wide-area mapping of neuronal excitability and synaptic transmission in acute brain slices.