Visual processing: First come, first served… T Stemmler1, M Fahle2 |
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1RWTH Aachen, Germany |
| How can humans achieve complex visual discriminations with saccadic response times below 150 milliseconds [Kirchner and Thorpe, 2006, Vision Research,46,1762-1776], given all the latencies in the visual system? Humans may achieve fast reactions by using arrival times of the first spikes (temporal order code), or else employing a very short integration interval (only a few spikes). To address the latter possibility, we distributed image presentation to several frames. Subjects indicated in a 2-AFC task which of two natural scenes contained an animal. Stimuli were presented either in one frame (5ms) or segregated over 3 frames (15ms). Subjects responded either by moving a throttle lever (experiment 1) or by saccadic eye movements, either without (experiment 2) or else with (experiment 3) a temporal gap (200ms) between fixation point disappearance and stimulus onset. In experiments 1 and 2, segmentation had no effect, ruling out a pure temporal order code. In contrast, experiment 3 revealed a clear decrease in performance for presentations segmented over 15ms. Our results indicate a temporal integration time window of 5 to 10ms, corresponding nicely with earlier reports on temporal resolution of roughly 10 ms [Kandil and Fahle, 2001, European Journal of Neuroscience,13,2004-2008]. |
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