Electroretinography and visually evoked potentials

Electroretinographic recordings (ERGs) and visually evoked potentials (VEPs) were performed as previously described (Nusinowitz et al., 2007). Briefly, mice were dark-adapted overnight, anesthetized and their eyes dilated. A gold wire electrode referenced to a similar gold electrode in the mouth, and a tail ground electrode, were used to record the ERG. For VEP recordings, a needle electrode was positioned subcutaneously 3 mm lateral to lambda over the contralateral visual cortex. The mouse head was positioned orthogonal to a large opening in a highly reflective Ganzfeld dome in which brief light flashes were presented using a Grass Photic Stimulator (PS33 Plus, Grass Instruments, Quincy, MA). Responses were amplified (CP511 AC amplifier, Grass Instruments), digitized (PCI-1200, National Instruments, Austin, TX) and computer averaged as described (Nusinowitz et al., 2007). ERGs were recorded under dark- and light-adapted conditions to evaluate rod- and cone-mediated retinal function, respectively. ERGs were recorded to achromatic flashes over a 4-log unit range of intensities (0.003–5.0 cd-s/m²). Cone-mediated ERG responses were obtained on a rod-saturating background (32.0 cd-s/m²). VEPs were recorded to the highest flash intensities (0.29–5.0 cd-s/m2) under dark-adapted conditions, which provided the most robust VEP signals to evaluate visual pathway function (Nusinowitz et al., 2007).