Asynchronous and synchronous activation of the two eye inputs in Thy1-ChR2 mice. A, Fluorescence images of the vertical section (left) and whole-mount (right) of retina of Thy1-ChR2 transgenic mice, showing that ChR2-EYFP (green) is expressed in ganglion cells and in their dendrites in the inner plexiform layer (IPL). PL, Photoreceptor layer; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; GCL, ganglion cell layer. Scale bar, 25 μm. B, Traces of subthreshold PSPs evoked by single pulses of blue LED light (5 ms, ∼0.4 mW/mm²) to the contralateral or ipsilateral eye (left 2 traces), respectively, or with 50 ms intereye interval (right traces) in the WT (top right) or Thy1- ChR2 (bottom right) mice. The bottom diagram indicates the light-stimulation pattern. C, Raster and PSTH plots of spike response evoked by trains of blue-light pulses (at 2.5 Hz) to the contralateral and ipsilateral eye with 50 (asynchrony, left) and 0 ms (synchrony, right) interpulse time difference between the eyes in the WT (top row) and Thy1- ChR2 (bottom) mice, respectively. The bottom diagram indicates the light-stimulation pattern.