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A.J. Valjakka, A. Tommiska, M. Saarelainen; The relationships between the light–response functions of the retina and superior colliculus in the non–drugged and freely moving rats . Invest. Ophthalmol. Vis. Sci. 2004;45(13):802.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To characterize the patterns of relationships between the response amplitude–vs–stimulus intensity –functions for the simultaneously measured retinal and superior colliculus's field potential responses after flashes in non–drugged and freely moving rats. The variation of the adapting field illuminance, predicted to modify the functions of above, was applied to see how the a–wave and b–wave components of the electroretinogram (ERG) contribute to the generations of the peak–1 and peak–2 response components of the superior colliculus (SC) by different flash intensities. Method:The ERGs were measured from the conjunctival surface of the eye ball and the central field potential responses from the superficial layers of the contralateral superior colliculus in the albino Wistar rats. The described novel method made possible the chronic recordings of the ERGs from the non–anesthetized or –drugged, freely moving, animals, and documentably produced the corneal–identical records as presently shown in anesthetized rats. Responses to flashes of different intensities (range: 6 log–units) were acquired under the adapting field illuminances of 0.1, 1 and 12 Lux. Results:The retinal a–wave, with comparable latencies to earlier findings on albino rats, showed in the all cases of adapting illuminances the two–terraced saturation of peak amplitudes by the increase of stimulus intensity. The condition of 12 Lux most clearly differed from the two other situations showing the reduced and prolonged plateau level of the first saturation phase which related to the lowest stimulus intensities. By the three different lighting situations the notch marking the beginning of the second saturation phase was consistently aligned around the same intermediate level of stimulus intensity. Noteably, the shapes of the above functions of the a–wave –peak (a representative of the b–wave onset), but not those of the b–wave –peak (a representative of the progressed stage of b–wave), were replicated, according to the magnified range of dynamicity, by the response functions of the peak–1 & –2 of the SC. The peak–latencies of the corresponding response components from the retina and SC did not show the concurring dynamics, but the mutual systematic variance by the flash intensity. Conclusions:The present data suggest that ERG field potential can ascribe the shape and magnitude of the resulting response dynamicity in the SC, that plausibly correlates to the separate and integrated functions of rod & cone photoreceptor cells in population.
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