Attention Facilitates Sequential Recruitment in the Perception of Motion Direction

Abstract

Sensitivity to the global direction of motion in a random-dot kinematogram (RDK) increases as the number of RDK frames is increased from 2 to about 10. This increase in sensitivity has been termed sequential recruitment and is thought to reflect cooperativity among motion detectors in V5. If attention is not a control state projected from executive to other brain areas, but rather cooperative activity in any brain area as multiple analysers converge on a single stimulus interpretation, then sequential recruitment should be impaired if RDKs are not attended. Motion direction sensitivity in 2-, 3-, 6-, or 10-frame RDKs was assessed under two conditions. In the first, RDKs appeared at central fixation on a random 80% of the trials and 6.5 deg to the right on the remaining 20%. Here, observers would attend the central but not the peripheral RDKs. In the second, RDKs appeared 6.5 deg to the right of fixation on 80% of the trials and centrally on the others. Observers would attend the peripheral but not the central RDKs. In both conditions, RDKs were 8%, 14%, 25%, 45%, or 80% coherent. Similar results emerged for both central and peripheral RDKs: Threshold was higher for 3-frame, but not 2-, 6-, or 10-frame RDKs when RDKs were unattended rather than attended, suggesting that recruitment is slowed in the absence of attention. These results support a network cooperativity view of attention and suggest that attention may influence relatively basic motion perception mechanisms.