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Lora Likova, Christopher Tyler; The human cortical network for coherent stereomotion processing. Journal of Vision 2008;8(6):539. doi: https://doi.org/10.1167/8.6.539.
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© ARVO (1962-2015); The Authors (2016-present)
To study the roles and interactions among a variety of cues for perception of stereomotion-in-depth, we used fMRI to investigate the whole brain network for the coherent stereomotion of a plane generated in different conditions: (i) correlated disparities and (ii) anticorrelated disparities (both generated in dynamic-RDS, i.e., cyclopean, at 25% dot density on a mid-gray field); (iii and iv) the same two conditions, but now non-cyclopean with the added cue of opposite monocular motions in the two eyes; (v and vi) the cyclopean and non-cyclopean forms of anticorrelated stereomotion but with dot density decreased to 2% and dot size increased to 4×4 pixels in order to recover both the depth and the stereomotion percepts (Cogan et al., 1993). Note that for fMRI, each of these conditions had a corresponding null that fully canceled any differential BOLD response to confounding factors, such as disparity per se, dynamic noise, disparate lateral motion, etc. The fMRI signal was measured with a GE Signa 3T scanner in a block design at 2s TR with 3×3×3 mm voxels. The lack of any motion-in-depth perception in the high-density anticorrelated stimuli resulted in no differential activation in the occipito-parieto-frontal network for correlated cyclopean stereomotion that we have found previously. In contrast, the low-density anticorrelated stimuli supported motion-in-depth perception and fully activated the network. Overall, the stereomotion network was activated by any condition that generated perceived stereomotion, implying that it has a generic role in 3D-motion processing. Paradoxically, the addition of monocular-motion cue to the disparity cue reduced the signal strength in several areas, posing challenges for theoretical models. The full array of results across cortical areas will be discussed in relation to their implications for understanding the mechanisms of dynamic stereopsis.
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