Abstract
Bisley and Goldberg (2003) showed that attention in the monkey, measured using thresholds in a perceptual discrimination task, remains at the goal of a memory-guided saccade throughout the delay. Because manual reaction time is also commonly used to measure attention, we sought to evaluate the effect of saccade planning on manual reaction time. We trained monkeys to release a bar in response to a Gabor patch (the probe), which appeared within the delay period of a memory-guided saccade to the location of a stimulus that flashed for 100 ms. The probe could appear at the saccade goal or at a location opposite to it. On some trials a distractor, identical to the saccade target, also appeared for 100 ms at either the saccade goal or at the opposite location. Both the saccade target and the distractor conferred a reaction time advantage to a probe at their spatial locations for about 350 ms after they appeared, as opposed to trials in which the probe appeared elsewhere. In addition, there was a sustained disadvantage at the goal of the saccade. This sustained disadvantage was eliminated when the distractor was flashed at the location opposite the saccade goal. These data are consistent with the idea that ‘attention’ as measured by reaction time differs from ‘attention’ as measured by perceptual sensitivity. They further suggest that neural activity in LIP, which predicts the pattern and time course of perceptual sensitivity, will not predict the time course of manual reaction time. Neural activity at a location further along in the process of sensorimotor transformation, like the superior colliculus or MIP, may better predict the patterns of reaction time seen in this task.
Supported by the W.M. Keck Foundation, the Whitehall Foundation, the James S. MacDonnell Foundation, and the National Eye Institute.