Abstract
High resolution monitoring of stimulus-evoked retinal neural activities is important for understanding retinal neural mechanisms, and can be a powerful tool for retinal disease diagnosis and treatment outcome evaluation. Fast intrinsic optical signals (IOSs), which have the time courses comparable to that of electrophysiological activities in the retina, hold the promise for high resolution imaging of retinal neural activities. However, application of fast IOS imaging has been hindered by the contamination of slow, high magnitude optical responses associated with transient hemodynamic and metabolic changes. In this paper we demonstrate the feasibility of separating fast retinal IOSs from slow optical responses by combining flicker stimulation and dynamic (temporal) differential image processing. A near infrared flood-illumination microscope equipped with a high-speed (1000 Hz) digital camera was used to conduct concurrent optical imaging and ERG measurement of isolated frog retinas. High spatiotemporal resolution imaging revealed that fast IOSs could follow flicker frequency up to at least 6 Hz. Comparable time courses of fast IOSs and ERG kinetics provide evidence that fast IOSs are originated from stimulus activated retinal neurons.
Highlights
High resolution imaging of stimulus-evoked retinal neural activities is important for understanding of visual information processing mechanisms in the retina
High spatial resolution intrinsic optical signals (IOSs) images revealed localized optical responses that correlated with cellular structures, and both positive and negative IOSs were observed in the stimulus activated retinal area (Fig. 2c)
The visible light flicker activated retinal neurons and elicited fast IOSs, and dynamic differential processing served as a high-pass filter to separate the fast IOSs from the slow, high magnitude optical responses that might be related to the metabolic changes in the retina (Fig. 2)
Summary
High resolution imaging of stimulus-evoked retinal neural activities is important for understanding of visual information processing mechanisms in the retina. It is well established that many eye diseases can cause pathological changes of photoreceptors and/or inner retinal neurons that lead to vision losses and even complete blindness. Different eye diseases, such as glaucoma [1, 2], diabetic retinopathy [3, 4], and macular degeneration [5], are known to target at different types of retinal neurons, causing localized lesions. Given the delicate structures and complicated functional interactions of the retina, detection of localized dysfunction of different cell populations requires a method that can examine stimulus-evoked retinal neural activities at high spatial and temporal resolutions
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