Removing direct photocurrent artifacts in optogenetic connectivity mapping data via constrained matrix factorization
Fig 3
PhoRC captures photocurrent artifacts across protocols and datasets.
a, Left: Inferred weights for the grid design, before and after subtraction. Weights are shown for a single Z plane. Right: Inferred weights before and after subtraction for a targeted experiment. Weights are shown for the entire Z stack. Green cross marks location of the postsynaptic cell. Applying PhoRC reduced the inferred synaptic strength of the connection nearest the postsynaptic cell, which was contaminated by photocurrent. b, Traces selected by taking 10 trials with the largest estimated synaptic current components, and ten trials with the largest estimated photocurrent components. Left panels: Observed currents, photocurrent estimates, and subtracted traces for a ChroME2f experiment. Right panels: same as in left panels but for a ChroME2s experiment. PhoRC successfully infers the photocurrent waveform in both cases, despite the use of different opsins. Estimates ignore PSCs which have higher latency than photocurrents. c, Left panels: average evoked waveforms for putative connections before and after subtraction for a ChroME2f experiment. Right panels: same as left, but for the ChroME2s experiment. In both cases, connection waveforms before subtraction display signs of photocurrent contamination, whereas waveforms obtained after subtraction have PSC-like profiles. d, PhoRC performance across grid datasets. Each column shows a different dataset. Responses are averaged across planes. From top to bottom: raw maps, photocurrent estimates, and inferred weights from the CAVIaR pipeline.