Removing direct photocurrent artifacts in optogenetic connectivity mapping data via constrained matrix factorization
Fig 2
A constrained low-rank model separates synaptic currents from photocurrents.
a, Scaled photocurrent traces from the grid experiments with ChroME2f. Colors correspond to different datasets; stimulation power used is shown on the right. Even with the same opsin, there is substantial cell-to-cell variability in the photocurrent waveform. b, Same as a, but for targeted experiments using ChroME2s. c, Schematic of the low-rank approach. The matrix of PSC traces (left) can be approximated as a single waveform scaled by a vector of amplitudes. d, The overapproximation constraint stops the estimated waveform from picking up PSCs. e, PhoRC estimates a baseline component which accounts for photocurrents from the prior trial. f, Simulated example showing the effect of the overapproximation constraint. Left: simulated traces containing a mixture of photocurrents and PSCs. Right: Photocurrent estimates for the traces shown on the left. The overapproximation constraint allows PhoRC to extract the photocurrent waveform while ignoring PSCs.