UCLA

Motion is a fundamental component of active vision, and visual motion is continuously generated during natural behaviors of an observer traversing through the visual environment. Motion arose from the independently moving objects, the observer’s self-locomotion, and eye- and body-movements can all generate retinal motion signals. Although primate extrastriate area MT is well known for its sensitivity to motion directions and speeds, less is understood about how MT represents dynamic motion signals, incorporates information related to self-movement, and contributes to motion-dependent spatial perception. This dissertation examines ecologically relevant visual motion processing through four complementary studies involving macaque, marmoset and human subjects. First, large-scale neurophysiological recordings from macaque MT showed that MT carries information of motion acceleration in a representation that can be decoded quickly and directly from population activity. These findings extend conventional accounts of MT beyond the encoding of instantaneous direction and speed. Second, the multi-area recordings in marmoset demonstrated that MT responses depended on the consistency between visual motion and the subject’s ongoing locomotion. MT activity was lower when self-generated visual motion remained coupled to the concurrent locomotion than during replay of the same visual input with this coupling disrupted. This modulation may help distinguish behaviorally consistent self-generated retinal motion from other signals. In the third study, the systemic delivery of an AAV vector encoding a calcium indicator was evaluated and functionally validated in marmoset MT with multi-scale optical imaging. This work opens the opportunity to investigate the functional architecture and organization of MT with longitudinal, robust and homogeneous optical imaging methods. Finally, the series of human psychophysical experiments used continuous nulling paradigm to characterize the spatial tuning of motion-induced position shifts, revealing how the perceived location of a moving target depends on the spatial relationship and interaction between the carrier and envelope motion. Together, these studies demonstrate that visual motion processing reflects not only location motion features but also temporal dynamics, behavioral context, and functional organization across space. In addition, they further provide methodological tools for investigating visual motion computations across levels of analysis and multiple primate models.