Purpose:
Vision requires that neurons encode the timing of events in the visual scene with high precision. Where in the retina is this precision generated?
Methods:
In vivo calcium imaging and electrophysiology in fish
Results:
We show that precision is first achieved in bipolar cells of the retina. Although bipolar cells are assumed to generate graded voltage responses to light, we find that the large majority also generate spikes in the synaptic terminal, phase-locked to a stimulus with a variance as low as 5 ms. Spike generation is stochastic and sparse in individual bipolar cells, but convergence of bipolar cell synapses onto postsynaptic amacrine and ganglion cells generates a reliable signal with similar temporal fidelity.
Conclusions:
These results suggest a new functional plan for the retina in which the conversion from slow analogue to fast digital signalling begins in the synaptic terminal of bipolar cells.
Keywords: bipolar cells • electrophysiology: non-clinical