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Aarlenne Z. Khan, J Douglas Crawford, Julio M. Martinez-Trujillo; Attention modulates saccade latency but not kinematics. Journal of Vision 2005;5(8):696. doi: 10.1167/5.8.696.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have observed that similar brain areas are activated during covert shifts of attention and during the execution of saccades, leading to the suggestion that the brain systems controlling these functions share similar neural substrates. In the present study we tested the extent of the functional overlapping between the two systems.
In the first of two conditions (full attention) we instructed subjects (n=6) to make saccades from a central fixation point toward a target that appeared randomly at two different eccentricities (12, 24 degrees) to the left or to the right of the fixation point. The target could have six different contrast levels (0, 2, 4, 6 and 10%). In a second condition (divided attention) the subjects performed the same task but we additionally instructed them to signal the occurrence of a transient contrast change at the central fixation point.
We found that in the divided attention condition the saccade latency was increased relative to the full attention condition; however the kinematics of the saccades (peak velocity vs. saccade amplitude) was the same in both conditions. We additionally found that changing the saccade target contrast in the full attention condition had a similar effect as in the divided attention condition, i.e., lowering saccade target contrast increased saccade latency but did not affect the kinematics. In general our results suggest that the level of attention directed to a stimulus influences visuomotor processing by modulating the relative saliency of that stimulus representation mainly during earlier stages of processing (similar to the effects of contrast), leaving the ultimate motor commands specifying the parameters for contracting the eye muscles relatively unchanged.
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