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Paul Gamlin, Matthew Ward, Lora Likova, Mark Bolding, Christopher Tyler; Cortical regions for the processing of stereoscopic motion in depth as revealed by fMRI in the alert rhesus monkey. Journal of Vision 2009;9(8):684. doi: 10.1167/9.8.684.
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Introduction. Although a high proportion of the motion selective cells in non-human primate motion areas are disparity-selective, there is no convincing evidence for cells specific to stereomotion-in-depth, and the neural basis of stereomotion processing remains obscure. However, recent fMRI studies in humans (Likova and Tyler, 2007) have revealed activity related to cyclopean stereomotion-in-depth (csMID; based entirely on temporal changes-in-disparity), with the earliest activation site in an occipito-temporal region anterior to hMT+ (the CSM region). To determine if there is an analogous area for csMID in the non-human primate, the present investigation used fMRI in the alert rhesus monkey combined with the same visual stimuli as used in the human study to search for cortical regions activated by csMID.
Methods. Data were acquired on a Varian/Magnex 4.7T scanner with a 60cm vertical bore. Stereoscopic visual stimuli were presented using an Avotec visual display system fitted with IR cameras for monitoring eye position. Using the same csMID stimulus paradigm as in the human study, we acquired BOLD functional images at a spatial resolution of 1.5×1.5×1.5 mm.
Results. The statistical maps generated from our fMRI experiments identified focal activation in two posterior regions: the fundus of the superior temporal sulcus (STS) and the IPS. The activation in the fundus of the STS appeared to be contiguous with MSTv, while that in the IPS appeared to coincide with VIP.
Conclusions. These results extend the analysis of motion in humans and macaques to cortical regions involved in the processing of motion-in-depth. The results strongly suggest that rhesus monkeys possess a cortical region in the STS specialized for the processing of csMID, comparable to the CSM region of humans. Furthermore, this study identifies potential targets for fMRI-guided neurophysiological studies of the cortical mechanisms of stereomotion processing in the rhesus monkey.
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