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Erik Runeson, Geoffrey Boynton, Scott Murray; fMRI responses in human MT+ depend on task and not the attended surface. Journal of Vision 2010;10(7):102. doi: 10.1167/10.7.102.
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© ARVO (1962-2015); The Authors (2016-present)
Previous neuroimaging studies show that the effects of attention on responses in the human visual cortex depend on the physical properties of an attended surface. For example, responses in MT+ have been shown to increase when attention is directed to a moving surface relative to a static surface. Separate studies demonstrate that responses in particular visual areas are also dependent on the task being performed. For example, responses in MT+ have been shown to increase during a speed discrimination task relative to color discrimination or shape discrimination tasks. We investigated the separable effects of the attended surface and task on responses throughout human visual cortex. Participants viewed two spatially overlapping but perceptually separable surfaces of dots, one continuously moving, and one nearly static. In alternating 20-second blocks composed of two-interval forced-choice trials, the participants attended to either the moving or the nearly static field, and performed either a speed discrimination task, or a color discrimination task. Consistent with previous findings, responses in early visual areas (V1-V3) did not depend on either the attended surface or the task being performed. However, responses in MT+ did vary with task, showing greater responses during speed discrimination than during color discrimination, but did not depend on whether a moving or a nearly static surface was being attended. The same pattern of responses was demonstrated in unstimulated areas of MT+ (contralateral hemisphere). The results suggest that overall task-dependent response modulation is independent of the physical properties of an attended surface.
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