Figure 1.

Spatial properties and quantification method. (A) NIR response to a vertical bar on a dark background. The presentation of patterned visual stimuli produced two predominant signals of opposite polarity, a negative signal (N) and a positive signal (P), that were spatially adjacent. Right: Grayscale bar representing fractional change in reflectance (dR/R). Negative signals correspond to a decrease in reflectance (dark regions). Conversely, positive signals correspond to a relative increase in reflectance (light regions). Areas that show no or slight reflectance change are gray regions (dR/R = 0). The response is localized with the stimulated retina. Scale bar: 6° of visual angle. Arrows: superior and nasal directions in the fundus image. Inset: the stimulus used to evoke the response. (B) Fractional reflectance time course of three ROIs. The signal intensity is plotted as a function of time. The fractional reflectance for each ROI was calculated (see Schallek et al.⁶). Both the positive (ROI P, white) and negative signal (ROI N, black) showed negligible deviation from baseline during the prestimulus epoch (0–2 seconds). Between 2 and 5 seconds (stimulus on), both signals appeared and developed in magnitude. In the poststimulus epoch (5–10 seconds) both signals slowly recovered toward the baseline reflectance (dR/R = 0). An ROI over the nonstimulated region of retina is also plotted (O, dashed lines). Reflectance changes were very small, most likely attributable to the biological noise of the system.