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Bjorn Ekesten, Peter Gouras; Cone Inputs And Oscillations In Murine Lateral Geniculate Nucleus. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6101.
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© ARVO (1962-2015); The Authors (2016-present)
To better understand the physiology of possible colour discrimination in mice, as well as the processing of neural signals from the retina to the lateral geniculate nucleus (LGN) to the visual cortex.
Single unit responses were recorded from the LGN of pentobarbithal anesthetized, normal mice by stereotactically guiding tungsten micro-electrodes into the nucleus. In order to detect cone selective and/or cone imbalances, 360 nm (UV) and 505 nm (green) LED stimuli were presented on a rod-saturating background. Receptive fields were mapped using backprojection of white stimuli onto a tangential screen.
The cells encountered have similar responses to both UV and green stimuli, although differences in the balance between the wavelengths were found from cell to cell. Colour opponent cells have not been found so far. The most striking finding is the extraordinary oscillatory responses observed in response to a single light stimulus. LGN neurons will respond with 5 or more oscillatory bursts at frequencies of about 10 Hz. The later oscillatory bursts may be more intense and comprise responses from more cells.
Differences in the strength of UV- and M-cone opsin driven inputs are found among LGN cells, but so far colour opponent cells have not been found. LGN neurons exhibit multiple oscillatory responses to a single light stimulus that must play a uniquely important role in murine visual behaviour. That a second cell may contribute to the later bursts in phase with the cell producing the initial burst, suggests coupling between cells. Hence, the oscillatory behaviour could be explained by excitatory recurrent collaterals synapsing onto both cells, rather than an intrinsic biochemical system in each cell producing the oscillatory responses.
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