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James Herman, Richard Krauzlis; Attention to color in the primate Superior Colliculus. Journal of Vision 2014;14(10):514. doi: 10.1167/14.10.514.
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© ARVO (1962-2015); The Authors (2016-present)
Activity in the intermediate layers of the primate Superior Colliculus (SC) is known to reflect the occurrence of behaviorally relevant visual events, even in the absence of orienting movements. Until recently, it was also believed that visual activity in the SC was largely color-blind. Here we tested whether color-related signals in the SC, which likely originate in the cerebral cortex, might also be exploited to detect behaviorally relevant, but purely chromatic, changes in the visual environment. We recorded the activity of neurons in the superficial and intermediate layers of the SC during a covert attention task employing dynamic "checkerboard" color stimuli described previously (Herman et al., 2013). The animal was presented with two color stimulus patches (3.25° radius, ~10° eccentricity) while maintaining central fixation and pressing a joystick. Prior to stimulus onset, a ring was flashed, cueing one of the two upcoming stimulus locations. The task was to respond to a change in saturation by releasing the joystick for changes at the cued location, and ignoring changes at the opposing "foil" location. Color changes were physically isoluminant, masked with luminance noise, and adjusted to be near the monkey's detection threshold. Most neurons showed dramatic, rapid increases in activity (latency 110-150ms) triggered by the color changes. Though the changes were near the animal's detection threshold, the activity they evoked was ~60% greater than the activity evoked by stimulus onset. Activity was also greater for changes that were detected than for those that were missed. Consistent with previous work, SC neurons showed a robust cueing effect – in most neurons (13/19 to date), we observed significantly greater activity for the cued stimulus compared to the foil. These results demonstrate that SC activity signals behaviorally relevant events even when those events involve color features distinctive of the primate visual system.
Meeting abstract presented at VSS 2014
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