Fig. 4.

(a) Photograph and (b) optical diagram of the near-infrared (NIR) light microscope for intrinsic optical signal (IOS) imaging. During measurements, an isolated frog retina is continuously illuminated by the NIR light. The visible light stimulator is used to produce a visible light flash for retinal stimulation. A multiple electrode array (MEA) system is used for concurrent ERG measurement of retinal activation. The dichroic mirror reflects visible stimulus light and passes the NIR recording light. The eyepiece camera is used to adjust a visible light stimulus aperture at the retina. In order to ensure light efficiency for intrinsic optical signal imaging, the beam splitter is removed from the optical path after the visible light stimulator is adjusted. The NIR filter before the high-speed camera is used to block visible stimulus light, and allows the NIR probe light to reach the detector for recording stimulus-evoked IOSs. Reprinted with permission from Ref. 116.