Figure 3.

High-performance Arch-mediated optical neural silencing of neocortical regions in awake mice. (A) In vitro data showing, in cultured neurons expressing Arch or eNpHR and receiving trains of somatic current injections (15 ms pulse durations at 5 Hz), the percent reduction of spiking under varying light powers (575 ± 25 nm light) as might be encountered in vivo. *, p < 0.05; **, p < 0.01, t-test. N = 7–8 cells for each condition. (B) Fluorescence images showing Arch-GFP expression in mouse cortex ~1 month after lentiviral injection (i; scale bar, 200 μm, ii, 20 μm. (C) Representative extracellular recordings showing neurons undergoing 5-second (i, ii), 15-second (iii), and 1-minute (iv) periods of light illumination (593 nm; ~150 mW/mm² radiant flux out the fiber tip; and expected to be ~3 mW/mm² at the electrode tip ~800 um away¹¹,¹²,²³). (D) Neural activity in a representative neuron before, during, and after 5 seconds of yellow light illumination, shown as a spike raster plot (top), and as a histogram of instantaneous firing rate averaged across trials (bottom; bin size, 20 ms). (E) Population average of instantaneous firing rate before, during and after yellow light illumination (black line, mean; gray lines, mean ± SE; n = 13 units). (F) Average change in spike firing during 5 seconds of yellow light illumination (left) and during the 5 seconds immediately after light offset (right), for the data shown in D. (G) Histogram of percentage reductions in spike rate.