High spatiotemporal resolution imaging is desirable for better understanding of dynamic information processing in the retina. Optical recording of stimulus-evoked neural activity can offer high spatial resolution with parallel monitor of many retinal neurons working together. We have recently demonstrated near infrared light imaging of fast intrinsic optical responses (FIORs) in activated amphibian retinas. High spatiotemporal resolution imaging of FIORs disclosed transient optical changes associated with electrophysiological responses. These FIORs were typically initiated from the center of the retinal area covered by the visible stimulus light pattern, and rapidly spread to surrounding area. Dynamic changes, i.e. amplitudes, polarities, and spreading patterns, of FIORs were dependent on the stimulus light intensity and delivery duration. In the retinal area covered by the visible light stimulus pattern, low strength stimuli evoked FIORs dominated by positive signals, but strengthened stimuli elicited negative-going responses. However, positive responses were consistently observed in surrounding area, beyond the edge of the stimulus light pattern at least 50 μm. Our experimental study and physiological analysis suggest that the negative FIORs are associated with the phototransduction of activated photoreceptors, and the positive FIORs result primarily from dynamic changes of second- and third-order neurons during retinal activation. Dynamic patterns and spreading waves of fast neural activity may reflect involvements of the feedback mechanisms, e.g. light adaptation and center-surround antagonism, of the retina.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.