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S. Kim, R. Jensen, J. F. Rizzo, III; Cortical Responses to the Patterned versus Natural Visual Stimuli on Rats. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4499.
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Studies on processing in primary visual areas usually use artificial patterned stimuli such as bars or gratings. As a result, little is known about the properties of activity patterns for the natural stimuli processed by the visual system. Furthermore, most results of electrophysiological study in rats have been obtained using limited number of recording electrodes. We conducted this study to verify the differences between the cortical responses to the patterned stimuli and those to the natural ones and to analyze the correlation among the multiple responding units.
Using the Sprague-Dawley rats, we performed the multi-single unit recording of the primary visual cortex using 32-channel multi-electrode array. For visual stimulation, we used various artificial patterns (light, bar, checkerboard and grating sinewave) and images of natural objects (animals, natural scenes and foods) those are flickering or moving. The signals acquired from the recording electrodes were sorted and analyzed to get activity map, spike ratio, and spike-triggered cross-correlation matrix.
Comparing the results from the patterned stimuli, natural ones didn’t show generalized increase of spike rate regardless of the orientation and motion of the stimuli. But we could find more recruitment of previously silent cells and significantly increased cross correlation among cells in results from natural stimuli.
Natural objects didn’t make the generalized increase of the visual cortical responses but rather triggered the active and complex neuronal connection. This results can be explained by the influence from the secondary/association area or activation of different processing mechanism.
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