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Gideon Y. Shalev, Michael A. Paradiso; The effects of natural scenes and saccades on V1 orientation selectivity. Journal of Vision 2005;5(8):596. doi: https://doi.org/10.1167/5.8.596.
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© ARVO (1962-2015); The Authors (2016-present)
In many experiments, control over visual stimulation is obtained by sacrificing much of the complexity of the natural world and visual behavior. For example, stimuli are presented on iso-luminant backgrounds and they are flashed instead of swept into view via saccades. In this experiment, we investigated the influence of complex natural backgrounds and saccades on the development of orientation selectivity in macaque V1. Four conditions were compared: Bars of light were either flashed into the receptive field or brought into the RF through a saccade. Different flash and saccade trials were run with iso-luminant gray and natural image backgrounds. Average response amplitudes were usually lower with a natural than gray background. Comparing flash and saccade conditions gave more variable results. From cell-to-cell the flash response was higher or lower than the saccade response. The differences in average response amplitude across conditions appeared to be consistent with gain changes rather than changes in optimal orientation or tuning width. There were also significant effects of the presentation paradigm on the timing of selectivity. Orientation selectivity generally appeared slower with a natural than a gray background. Selectivity usually developed faster when stimuli appeared from a flash rather than a saccade. Comparing the least (flash/gray) and most natural (saccade/natural) paradigms, there was often a significant difference in the timing of maximal selectivity (tens of msec). These results indicate that the more natural paradigms recruit additional neural circuitry that decreases response amplitude and delays orientation selectivity. This suggests that in natural visual situations, the earliest form-selective V1 response carries potentially important information about stimulus context that is different from that available in reduced paradigms.
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