Purchase this article with an account.
Melissa Saenz, Geoffrey M Boynton; The role of competing stimuli in feature-based attention. Journal of Vision 2003;3(9):727. doi: 10.1167/3.9.727.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We used functional MRI in humans to evaluate the role of competing stimuli in non-spatial, feature-based attention. We have previously shown that attention to a stimulus feature (a particular motion direction or color) increased human visual cortical responses to a spatially distant stimulus that was ignored, but had the attended feature (Saenz, Buracas & Boynton, 2002). In that experiment, selecting the target stimulus required filtering out an overlapping distracting stimulus. In the spatial attention literature, the strongest neuronal modulations are typically found when multiple stimuli compete for attentional selection. Here, we repeated our feature-based attention motion experiment without the overlapping stimulus to assess the role of distractors. Two stimuli, one attended and one ignored, were presented to the left and right of fixation. In the previous experiment, the attended stimulus was a circular aperture of two transparently overlapping fields of upward and downward moving dots; subjects performed a speed discrimination task on the upward vs. downward moving fields in alternating blocks during each scan. In the new experiment, the attended stimulus was a single field of dots moving upward vs. downward in alternating blocks and subjects performed the task on that field. In both experiments, the ignored stimulus was a circular aperture of a single field of dots moving either upwards or downwards, unchanging in direction during each scan. As in our original experiment, we again found that responses in multiple cortical visual areas (V1, V2, V3, V4, V3A, MT+) to the unchanging, ignored stimulus increased when subjects attended the matching direction of motion in the attended stimulus. The magnitude of the effect was similar in the experiments with and without distractors. Thus, neuronal modulation due to feature-based attention did not require the presence of competing stimuli.
This PDF is available to Subscribers Only