all-optical platform for cultured neurons

Since April last year, we have been working toward our first goal: establishing an all-optical platform for cultured neurons, including human iNeurons, rodent iNeurons, and primary neuronal cultures. Thanks to the hard work of my master's student, Isabel de Vicente, and our collaborator from Marijn Kuijpers' lab, Sharon Goudemans, we have made significant progress.

For optical stimulation (optogenetics), we have obtained neurons from rat primary cell cultures that respond robustly, reliably evoking multiple action potentials. See the figure below, showing a 200 ms illumination with a 470 nm LED.

For optical voltage recording, we are finally achieving a temporal resolution high enough to record individual action potentials. The figure below shows optical signals from the Archon1 voltage indicator expressed in a primary cultured neuron (top trace), together with a whole-cell patch-clamp recording (bottom trace). The Archon1 signals were measured from the region of interest (ROI) shown on the left.

The time-expanded traces below show that the optical signals faithfully follow individual action potentials.

The temporal resolution improved even further with higher concentrations of the viral vector. The first trace below shows individual action potentials evoked every 500 ms, recorded with a 2 ms exposure time (500 fps), while the second trace shows action potentials evoked every 1 second, recorded with a 1 ms exposure time.

We still need to improve the resolution further, but things are starting to look very promising!