How does a synapse encode a visual stimulus?
We recently published a paper in Nature Neuroscience titled “An amplitude code transmits information at a visual synapse“. Using the reporter iGluSnFR to image the neurotransmitter glutamate, we achieved the resolution to count individual synaptic vesicles as they are released from a single active zone in vivo. This revealed that bipolar cells transmit the visual signal using a hybrid coding strategy involving changes in both the rate and amplitude of synaptic events. We are now, for the first time, able to investigate the vesicle code that transmits information across a synapse, much as counting spikes has allowed investigation of information coding within neurons.