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Claudine Habak, Jocelyn Faubert; Motion facilitation across space and the role of attention. Journal of Vision 2002;2(7):641. doi: 10.1167/2.7.641.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Much work has shown attention to modulate motion perception. Raymond et al. (1998, Vision Res., 38, 2863–67), have demonstrated that a first RDK (prime) affected motion sensitivity to subsequently presented RDKs (probe), when both were in the same spatial location. Using a similar task, we assessed whether attention modulates motion sensitivity for sequentially presented RDKs in two different spatial locations, and for both central and peripheral visual fields.
Methods: RDKs with limited-lifetime dots (1 jump) were used. Dots appeared for 26.7 msec and inter-frame interval was 26.7 msec. For central visual field measures, RDKs were presented in one of two adjacent circular 10° regions on either side of fixation, and for peripheral measures, in one of two 20° regions separated by 60°. Two different primes were used: 1- single: half the dots were stationary and half the dots moved in one of four directions (left, right, up, down); 2- dual: half the dots moved in one direction along the horizontal plane and half along the vertical plane. The probe RDK moved in one of the four aforementioned directions. Task: a cue word (horizontal or vertical) appeared for 653 msec indicating the motion plane to attend to. The prime then appeared for 533 msec, followed by a 200 msec interval, and finally the probe for 107 msecs. Two responses were required: 1- the direction of the prime, and 2- the direction of the probe. The method of constant stimuli was used, and only trials in which the first response was correct were used for threshold calculation.
Results: Thresholds were lower when prime and probe moved in the same direction than in orthogonal (baseline) or opposite directions. Attention did not enhance this facilitation, and even diminished it slightly.
Conclusion: Motion in the same direction leads to facilitation across space. Attention for one region may inhibit facilitation in another, unlike what is found when both prime and probe are in the same spatial location.
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