Figure 7.
The waveforms of the light responses of FPs, photoreceptor axon terminals, and LMCs under dark-adapted (DA) and light-adapted (LA) conditions. A, FP (gray) and axon (black) responses compared by equating their baselines, just before the stimulus. B, Postsynaptic LMC responses (black traces) compared with photoreceptor axon transmembrane responses (gray traces) calculated from the data in A by subtracting the FP response from the axon response. The transmembrane potential traces have been inverted for comparison with LMC because the photoreceptor axon–LMC synapses are sign inverting. Note that subtraction of the FP has produced a transient presynaptic signal in the axon that is capable of contributing to the transient postsynaptic response of the LMC. Stimuli: DA, 300 ms light pulse of 106 photons/s; LA, 300 ms contrast steps, ±1 against a background of 106 photons/s.