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Adriane E Seiffert; Dissociating neural correlates of attentional tracking and attention to visual motion. Journal of Vision 2003;3(9):868. doi: 10.1167/3.9.868.
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© ARVO (1962-2015); The Authors (2016-present)
People can track the motion of objects with focused attention to different object positions over time. Do the brain regions engaged in this task reflect a specific position-tracking mechanism or just visual attention to motion? This fMRI experiment measured brain activity during an attentional tracking task and a comparable motion discrimination task to dissociate between brain areas responsive to tracking and attention to motion. All displays showed superimposed high-contrast color and low-contrast luminance radial gratings moving in opposite directions. Observers see motion in the direction of the luminance grating, unless they attentionally track the components of the color grating (Cavanagh, 1992, Science. 257:1563–5). Four observers discriminated the speed change of either the color or luminance grating, alternating gratings between 15-second blocks. Task difficulty was counter-balanced such that either the color or luminance task was more difficult in alternate sessions with the same subjects. Standard GLM analyses with two predictors corresponding to the two tasks were performed on individual subject data. Greater activity specific to the color tracking task (independently of task difficulty) was found in all subjects bilaterally in the superior parietal lobule, posterior intraparietal sulcus and the frontal eye fields. No area was consistently active specifically to the luminance task across the difficulty manipulation and in all observers. The response of the motion-sensitive center, MT+/V5 (localized with separate scans), did not show significant differential activity between color and luminance tasks in most cases. Similar results were found when subjects tracked a texture grating instead of color (N=2). Taken together, these results suggest that posterior parietal structures are intimately involved in attentional tracking changes in object positions beyond the role they might play in attending to visual motion.
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