V5/hMT responds to the stereoscopic motion induced by binocular disparity: A preliminary fMRI study

Purpose: To identify the regions responding to the stereoscopic motion induced by binocular disparity and investigate the relationship between the response intensity of these regions and speeds of spatial motion. Methods: The stereoscopic stimulus applied Random Dot Stereogram (RDS) distributed as checkerboard and a series of continuous disparities formed a dynamic stereoscopic stimulus. Observer needed to watch some static stimuli and dynamic stimuli moving in depth direction. The speeds of dynamic stimulus consisted of three levels: 0.315 degree/s, 0.63 degree/s, 1.26 degree/s. The functional Magnetic Resonance Imaging (fMRI) was used to sample the Blood Oxygen Level-Dependent (BOLD) signals and identify the regions sensitive to stereoscopic motion. Results: The dynamic stereoscopic stimulus can activate the hMT/V5 in a stronger degree than static stereoscopic stimulus. Besides, the signal intensity increased with the speed. The most reasonable explanation is that a large number of neurons sensitive to spatial motion exist in this region. Conclusion: The study reveals preliminarily that the human cortex hMT/V5 processes the information of spatial motion.