Fig. 2: Photoacoustic modulation of ex vivo wild type and degenerated retinae.
a The ex vivo retina was placed on a multi-electrode array with the photoacoustic film against the photoreceptor layer. b Top: schematic of the laser sequence for photoacoustic stimulation (laser pulse energy Ep = 10 µJ, pulse duration dpulse = 4.2 ns, pulse repetition frequency frep = 1.9 kHz, bursts of duration db = 10 ms). Each laser pulse is converted by the PA film into an acoustic wave with a duration dUS = 36 ns. Bottom: Example high-pass filtered single electrode recording displaying elicited spikes following a photoacoustic stimulation. Red shaded area: laser on. Inset: action potentials following stimulation. c Examples of Long Evans (LE, cyan) and P23H (brown) retinal ganglion cell (RGC) mean firing rate following responses to photoacoustic stimulation. Gray shaded areas: 99% bootstrapped CI. Red shaded area: PA stimulation. d Heatmaps of normalized firing rates for responsive LE RGCs (left, n = 100) and P23H RGCs (right, n = 88). Red shaded area: PA stimulation. Cells with excited responses display an increase in firing rate after photoacoustic stimulation (red), and cells with inhibited responses display a decrease in firing rate (blue). e Percentage of cells modulated by photoacoustic stimulation per stimulation site. LE: 74% (4 rats, n = 10 stimulation sites), P23H: 39% (4 rats, n = 12 stimulation sites). *** P < 0.001, two-sided Mann-Whitney U test. f Firing rates of LE and P23H RGCs during baseline (basal) and following stimulation (stim) (LE, n = 82 RGCs within stimulation range; P23H, n = 72. *** P < 0.001, two-sided Wilcoxon signed-rank). g Latencies of RGC responses for LE (n = 82) and P23H (n = 72, *** P < 0.001 two-sided Wilcoxon rank-sum). Dashed black line in (d) and (g): 45-ms cutoff for slow- and fast-latency responses. Box plots (e–g) central line: median, lower and upper bounds: first (Q1) and third quartiles (Q3), whiskers extend to the most extreme data points within 1.5 times the interquartile range from Q1 and Q3. Dashed line: mean.
