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Lora T. Likova, Christopher W. Tyler, Paul D. Gamlin; Frontal cortical activation by stereoscopic motion-in-depth. Journal of Vision 2006;6(6):625. doi: 10.1167/6.6.625.
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Purpose. Motion-in-depth creates a profound perceptual experience involving many aspects of neural processing. We have previously identified areas specific to stereoscopic motion-in-depth in human posterior cortex (Likova & Tyler, 2003; 2004). Now we use whole brain fMRI to explore the entire stereomotion network.
Methods. fMRI responses were obtained on a 3T scanner in 40 axial slices, 3 mm thick, at 3s TR. Both the test and the null stimuli were dynamic random-dot stereograms. Cyclopean stereomotion was generated by disparity modulation-over-time with no correlated retinal motion. Exp1: Stereomotion (test) was contrasted with a zero-disparity plane (null). Exp2: The null periods incorporated the stereomotion-disparities but as fixed planes. The observers maintained steady fixation, suppressing vergence tracking, and performed an attention control task. Retinotopic areas, hMT+ and vergence regions were mapped in separate sessions.
Results. In addition to the previously-identified areas, stereomotion activated four distinct frontal-lobe sites: (i) a site in the precentral gyrus that may be homologous to a neurophysiologically-identified stereomotion region posterior to the arcuate sulcus in monkey cortex (Dearworth, Li & Gamlin, 2004), (ii) in the dorsolateral prefrontal region, known to be involved in attentional control and sequencing behaviors, (iii) in the paracentral sulcus, and (iv) in the ventrolateral prefrontal cortex, ventral to Broca's area, implicated in inhibitory decision making.
Discussion. Stereomotion perception is a complex process incorporating, among others, dynamic sensory and attentional tracking components. The prominent sites of human frontal cortical activation may well reflect the involvement of such higher level processing. Their roles in the stereomotion network will be discussed.
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