Abstract
Multifocal electroretinogram (mfERG) allows objective assessment of retinal function by analyzing a spatial distribution of local ERG under light-adapted conditions (Sutter and Tran, 1992). In order to elucidate the spatial distribution of retinal light responses in cyprinid fish, we applied the mfERG (VERISTM, EDI) technique to an eyecup preparation of the carp. The carp mfERG show large responses were found in the ventral-temporal (VT) retina region. In contrast, small responses were found in the dorsal-nasal region and optic nerve located in the center of the retina. We also confirmed that detailed spatial distributions of the VT region by opening up the eyecup preparation. Consequently, carp mfERG was different from the human's one that has a peak at the fovea. This result was in agreement with the high density of retinal ganglion cells in the VT region of cyprinid zebrafish (Mangrum, Dowling, and Cohen, 2002). Thus the VT retinal region of the carp might be corresponded to the human fovea. Moreover, this region might be served to enhance vision in the upper-frontal visual space to feed on bugs fallen on the water surface.
