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Milena Kaestner, Ryan T. Maloney, Marina Bloj, Julie M. Harris, Alex R. Wade; Attentional state modulates responses to motion-in-depth stimuli across striate and extrastriate visual areas. Journal of Vision 2017;17(15):16. doi: 10.1167/17.15.16.
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Extrastriate areas associated with two-dimensional motion processing have also been shown to process motion-in-depth (MID) stimuli. These areas can be driven by the visual components that define MID, such as changing disparity (CD) and inter-ocular velocity differences (IOVD). However, the response profiles of areas involved in the subjective perception of MID remain unclear. Here, we used fMRI and an attentional manipulation to investigate this.
A random-dot stimulus containing either CD or IOVD cues was presented continuously throughout each scan. 500ms probes corresponding to 3 different tasks (MID modulation, contrast dimming and fixation change) were randomly interleaved throughout the scan. In 15 second blocks, participants (N=10) were cued to attend to and detect probes of one task type, while ignoring the others. Thus, attentional state changed systematically throughout the scan, but the stimulus remained constant.
Attention to either contrast or MID resulted in greater modulations in early visual areas (V1, V2, V3) than in the fixation task. Attention towards MID also resulted in increased activation in MT and MST, though no differences were found between MID conveyed by CD or IOVD. Additionally, responses across early visual and extrastriate areas could be differentiated depending on whether the attended probe type was detected or missed. Motion selective areas showed an increased BOLD response during detected MID probes, but did not show a difference between detected and missed probes on the contrast task. These results imply that activity in extrastriate motion areas is correlated with the subjective perception of MID.
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