Fig. 1. Transient and dynamic polarization sensitivity in a lamina monopolar neuron. (A) Hyperpolarizing responses of lamina monopolar neurons (LMCs) to successive 0.2s flashes of polarized light at 1s-1 as the polarizer rotates through 540°. The lower trace is the response of a photodiode, which captures a small fraction of the stimulus signal from behind a vertically oriented polarizer. The largest pulses on the lower trace (arrows) indicate vertical polarization (
=0°) and the smallest pulses (arrowheads) indicate horizontal polarization (=90°). Because the photodiode response is highly nonlinear, the amplitudes indicated in the stimulus trace do not reflect the correct intensity of the vertical e-vector in this or any of the figures. (B) Response of the same LMC (upper trace) to a changing e-vector (at the same intensity as in A) produced by a rotating polarizer. The stimulus light comes on at the left of the panel (t=2.0s) and polarizer rotation commences 5.5s later. The peaks and troughs of the lower trace indicate polarization angles of 0° (vertical) and 90° (horizontal), respectively. The dashed line corresponds to the membrane resting potential of the LMC (modified from Glantz, 1996a). (C) Response of a different LMC to a rotating polarizer with steady-state exposures at =90° at the left of the panel and =10° at the right. Note the very modest differences between the two steady-state responses compared with the response to the same two e-vectors during polarizer rotation.
