Synaptic organization of retinotectal connections of the frog application of pulse triggered averaging.

Pulse-triggered averaging technique was applied to retinotectal connections of the frog. An extracellular single unit was first isolated from the terminals of retinal fibers, and then intracellular responses were recorded from a tectal neuron in the vicinity of the extracellular recording electrode. Intracellular potentials in response to a moving stimulus were averaged by triggering with the isolated presynaptic impulses. The results show that "on-off" retinal fibers monosynaptically excite E-E type (EPSP at "on" and "off" of light) and EI-EI type (EPSP-IPSP at "on" and "off" of light). One of the E-E type neurons was identified as a large ganglionic neuron in layer 8.