Intrinsic optical imaging of stimulus-modulated physiological responses in amphibian retina.

We demonstrated near-infrared light imaging of stimulus-modulated physiological activities in an isolated frog retina using transient intrinsic optical responses (TIORs). While low-strength visible-light stimuli evoked TIORs with positive polarity, strengthened stimuli elicited additional negative TIORs. Our experimental study and physiological analysis suggest that the negative TIORs are associated with photoreceptor response, and the positive TIORs result primarily from dynamic changes of postphotoreceptor response during retinal activation. In coordination with the sophisticated design of visible-light stimulation protocols, optical imaging of TIORs promises an important application for noninvasive assessment of retinal photoreceptor and inner neurons.