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Jan Kremers, Vladislav Kozyrev; The influence of spatial displacement between stimulus and receptive field upon the responses of LGN cells. Journal of Vision 2003;3(9):368. doi: 10.1167/3.9.368.
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© ARVO (1962-2015); The Authors (2016-present)
In previous experiments, we found that the perception of flicker strength in a circular stimulus can be changed by altering the relative temporal phase of a simultaneously flickering surrounding annulus: weak flicker is perceived when the two stimuli are modulated approximately in phase; counterphase modulation of center and surround stimuli will result in strongly perceived flicker. The response amplitudes of LGN cells vary in a similar manner with relative phase, when the stimuli are spatially matched to the receptive fields (RFs) of the cells. From this it was concluded that the physiological basis of flicker perception is already present in the LGN. To strengthen this conclusion, it is necessary to study all responding cells, including those for which stimulus and RF do not match. We therefore studied the responses of marmoset LGN cells to the above mentioned combined stimuli varying the relative phase between center and surround and varying the spatial displacement between the stimuli and the RFs. It was found that, when the center and surround stimuli were modulated in phase (resulting in a full field stimulation), the responses of the cells don't change strongly with changing spatial displacement. As a result, all cells that are covered by such a stimulus, will respond similarly. This might cause a weak perceived flicker in the center stimulus. On the other hand, the responses strongly depend upon spatial displacement when the temporal phase difference between center and surround stimuli is large. Thus, the responses of all cells covered by the stimulus can be very different, depending upon their spatial position. This may introduce a spatial signal for cortical cells and cause a strongly perceived flicker. The responses of the cells were compared with predictions assuming that the RF is a linear summation of center and surround Gaussians responsivity profiles. The actual responses and the predictions were in qualitative agreement with each other.
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