Bottom-up effects modulate saccadic latencies in well-known eye movement paradigm.
A well-known eye movement paradigm combines saccades (fast eye movements) with a perceptual discrimination task. At a variable time after the onset of a central arrow cue indicating the target direction [the stimulus onset asynchrony (SOA)], discrimination symbols appear briefly at saccade target and non-target locations. A previous study revealed an unexpected effect of SOA on saccadic latencies: latencies were longer in trials with longer SOAs. It was suggested that this effect reflects a top-down process as observers may wait for the discrimination symbol to appear before executing saccades. However, symbol onsets may also modulate saccade latencies from the bottom-up. To clarify the origin of the SOA effect on latencies in this paradigm, we used a simplified version of the original task plus two new symbol onset conditions for comparison. The results indicate that the modulation of saccadic latencies was not due to a top-down strategy, but to a combination of two opposing bottom-up effects: the symbol onsets at the target location shortened saccade latencies, while symbol onsets at non-target locations lengthened saccade latencies.
van Stockum
Saskia
S
Van der Veer Institute for Parkinson's and Brain Research, Christchurch, New Zealand. vanev008@student.otago.ac.nz
Macaskill
Michael R
MR
Anderson
Tim J
TJ
D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D003463:Cues; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D013647:Task Performance and Analysis; D055815:Young Adult