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X. Fan, B. Lei, K. Zhang, G. Yao; Optical Mapping of Visual Cortex Responses in Mice With Pure Rod or Pure Cone Functions. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3847.
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© ARVO (1962-2015); The Authors (2016-present)
Since mouse models have become increasingly significant in vision research, it is important to fully understand their visual functions. We used optical imaging of intrinsic signals to map the visual cortex of three mouse strains under visual stimuli of different intensities.
Experiments were performed on 29 wild type C57BL/6J mice, 14 rho-/- (rhodopsin knockout) and 12 cpfl1 (cone photoreceptor function loss 1) mice. Optical imaging was conducted on dark-adapted, anesthetized animals through intact skulls. A green LED (505 nm in wavelength) was used as the stimulation and the light intensity ranged from 108.6 to 1015.5 photons/cm2/s. The mouse’s cortex was illuminated by a monochromatic light of 630 nm wavelength. The image stacks under the same stimulus for each mouse were processed and averaged using a custom made software.
Under stimulation of high intensities (above 1013.6 photons/cm2/s), the cortical responses of C57BL/6J and rho-/- mice showed triangular patterns. But the patterns of rho-/- mice clearly lacked the posterior medial part of the C57BL/6J mice. At a lower intensity of 1011 photons/cm2/s, the cortical response of C57BL/6J mice turned into a rectangular pattern. The visual cortex signal of rho-/- mice started to appear at this low intensity with a very small activated area. The intrinsic signal map of cpfl1 mice consistently resembled a circular disk at stimulation intensities from 1011 to 1012.2 photons/cm2/s. The response from cpfl1 mice decreased when the stimulus intensity was higher than 1012.2 and disappeared at the highest intensity. These visually different cortical maps were further confirmed by calculating the center of activity (COA) using digital image processing.
The visual cortex maps of the three mouse strains are significantly different even with the same stimulus intensity. Such variation might be associated with the corresponding photoreceptors function loss in rho-/- and cpfl1 mice.
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