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X. Yao, Y. Zhao, C. Gorga; Optical Visualization and Characterization of Stimulus-Modulated Physiological Responses in Isolated Retina. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2007.
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© ARVO (1962-2015); The Authors (2016-present)
Stimulus evoked fast intrinsic optical responses (FIORs) in retina promise new methodology for high resolution assessment of retinal function. We have recently demonstrated near infrared light imaging of FIORs, and characterized their relationships to stimulus-modulated physiological responses in isolated amphibian retina.
A near infrared light video microscope was developed to image stimulus evoked FIORs in isolated frog retina. While a white light flash was used to stimulate the retina, a continuous near infrared light was used to detect transient intrinsic optical changes in activated retina. Functional images were reconstructed by processing fast CCD/CMOS images to show dynamic optical changes, typically with unit of dI/I, where dI is dynamic optical response associated with retinal activity and I is background light intensity.
High resolution spatiotemporal imaging disclosed FIORs closely correlated with frog ERG response. Both positive and negative FIORs were observed in stimulus activated retina. The dynamic patterns and polarities of FIORs were stimulus dependent. While low strength stimuli evoked FIORs dominated by positive signals, enhanced stimuli could activate negative-going response. Depth-resolved imaging indicated that negative-going and positive-going FIORs result primarily from the retinal photoreceptor and inner retinal layers, respectively. Soma- and dendrite-like patterns were observed in the functional images recorded from the inner and ganglion layers, respectively.
Our experimental results 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. Near infrared light detection of fast intrinsic optical responses is comparable to ERG measurement, but can provide noninvasive, high resolution spatiotemporal imaging of retinal function.
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