Abstract
Purpose: :
To validate near infrared (NIR) reflected light imaging of fast intrinsic optical signals (IOSs) that have time courses comparable to ERG responses.
Methods: :
A fast confocal imager was constructed to demonstrate reflected light detection of transient IOSs in isolated frog (Rana Pipiens) retinas. While an acousto-optic deflector (AOD) was employed to produce rapid, vibration-free scanning of the near infrared (NIR) illumination light, an ultrafast (68,000 lines/s) line-scan camera was used for parallel recording of multiple (1024 pixels/line) retinal points. During the experiment, a while light flash was used for retinal stimulation. By differentiating the pre-stimulus and after-stimulus images, dynamic IOS images were constructed to characterize spatial and temporal properties of stimulus-evoked neural activity in the retina.
Results: :
Using the home-built confocal imager, NIR light imaging of fast retinal neural activity was demonstrated. Fast (>50 KHz) NIR light imaging disclosed transient reflected light changes tightly correlated with the stimulus-evoked retinal activity. High resolution (~um) images revealed both positive (increasing) and negative (decreasing) IOSs in adjacent retinal areas. Depth-resolved confocal imaging suggested the existence of multiple sources of transient IOSs, and different retinal neurons might contribute to the IOS image with variable time courses and polarities.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • electrophysiology: non-clinical