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Son-Hee Lyu, Zhong-Lin Lu, George Sperling; Cortical areas involved in processing planar stereo motion. Journal of Vision 2011;11(11):336. doi: 10.1167/11.11.336.
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Brain regions involved in processing planar steroptically-defined motion (third-order motion) were investigated using fMRI. Visual stimuli that produced the perception of a depth-defined grating, translating in the fronto-parallel plane, were produced in a dynamic random dot stereogram (DRDS). DRDS stimuli contain no luminance or texture cues to motion, nor any monocular temporal or spatial information. Features for motion perception are available only through stereoptically combining the images in the two eyes. Method: In a Siemens 3T Trio system, we compared cortical BOLD activations generated by motion of the stereo-depth grating, depth-reversal-flicker of the stereo grating, and a stationary stereo grating to a flat stereo plane (the baseline). A block design was used to present the three stereo conditions (stereo motion, stereo flicker, and stationary stereo) interleaved with the baseline condition to six subjects. Separate functional localizer studies defined 13 cortical regions of interest (ROI). Results: V1 and V4 showed no activation differences to any stereo condition compared to zero-disparity baseline. The earliest areas activated by the stereo gratings were V2, V3, and V3a; these retinotopic areas did not differentiate the three stereo conditions. Dorsal intraparietal sulcus [DIPS], middle temporal and middle superior temporal cortex [MT, MST], inferior temporal sulcus [ITS] and cyclopean stereomotion area [CSM] showed significant activation to all stereo conditions with greatest activation for stereo motion. Precentral sulcus (PrCS) activated significantly only for stereo motion. Posterior superior temporal sulcus [STSp] and supramarginal gyrus [SMG] showed no difference in activation for stereo motion and flicker, but showed negative activation for stationary stereo relative to baseline, suggesting that these regions may suppress stationary patterns in favor of dynamic ones. Conclusion: The great diversity of brain activations for stereo-defined stimuli suggests that stereo information is extracted early and processed subsequently like other pattern and motion information.
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