Figure 1.

Schematic diagrams of the experimental tasks. A, Fixation task. Either visual or acoustic stimuli were presented in the frontal hemifield without behavioral constraints. To receive a reward, the subject was expected to make a saccadic eye movement to the location of a stimulus and to maintain fixation on the source until it was turned off. B, Memory-saccade task. This task began with a visual fixation event at the straight-ahead position. While the subject maintained fixation, a visual or an acoustic target was presented elsewhere. The time elapsed between the offset of the target and the offset of the visual fixation event, illustrated with Δ, is the delay period. The subject was required to maintain fixation on the LED straight ahead for the entire duration of the delay period and not to respond until it was turned off. The delay period was varied randomly (200–1400 ms) from trial to trial. C, Summing localization task. Pairs of noise bursts were presented from speakers located at either (±31°, 0°) or (±60°, 0°) with interstimulus delays, illustrated with Δ, ranging from 0 to 1000 μs. These stimuli were presented in the context of the memory-saccade task. Lead ON, First stimulus of the pair to be turned on; Led OFF, second stimulus of the pair to be turned on. D, Franssen effect task. Pairs of single-tone stimuli were presented from speakers located at (±31°, 0°) while the subject maintained fixation on an LED located straight ahead.