On September 26, 2012, The Journal of Neuroscience published online a research article entitled " Distinct functional organizations for processing different motion signals in V1, V2, and V4 of macaque ". This work was carried out by Mr. Xu An (a visiting graduate student from USTC), assistant investigator Mr Gong Hongliang, and Dr. Wei Wang along with other colleagues in Dr. Wang’s Lab at ION, CAS.

Motion perception requires processing of motion signals consisting of direction, speed and the axis or trajectory of motion, as defined by a moving object. In comparison to the representation of orientation, how early visual cortices of primate ventral pathway are functionally organized in processing these different motion signals is an important question for our understanding of motion perception. Using drifting visual-noise stimuli and intrinsic optical imaging along with cytochrome-oxidase staining, researchers in Dr. Wei Wang Lab discovered that the orientation domains in V1, V4 and the pale and thick stripes of V2 of macaques that processed orientation signals also served to process motion signals associated with the axis and speed of motion. In contrast, direction-selective signals within the thick stripes of V2 are processed independently of motion speed by separate neuronal populations. Furthermore, the population responses encoding orientations and motion axes could be precisely reproduced by a linear spatio-temporal energy model.

The central issue addressed in this study concerns the cortical organization and processing of different components of motion signals in macaque ventral visual pathway (see Figure below). The findings of population responses with dual functions within orientation columns of V1, V2, and V4 directly support the notion that the linear representation of the temporal series of retinotopic activations may serve as another motion processing strategy in primate ventral visual pathway, helping to resolve the ‘‘aperture problem’’ as well as contributing to the interactions between form and motion. This study also provide direct evidence at the population level of macaque early ventral pathway for human psychophysical observations known as ‘‘motion-streak’’ or ‘‘speed-lines’’ as well as for the perception of ‘‘sampled motion’’ in the cinema (24 frames per second, fps) and on television (30 or 60 fps), for example, the cartoon animation. 

A.  The schematic diagram illustrates motion direction, speed and axis or trajectory generated by a moving object in the case of sampled motion, in which each bulb is lighted sequentially in rightward direction at different times without actual position changes (no real motion involved but a series of retinotopic activations in time).

B. Summary of the main findings. A schematic of the segregated and parallel pathways for distinct processing of different motion signals in V1, V2, and V4 of macaque ventral visual pathway, encapsulating our findings with those of previous studies. Here we illustrate only the main feed-forward projections. Essentially, the orientation domains mapped in V1, V2, and V4 not only process contour orientation signals but also process motion signals associated with motion axis and speed. In contrast, the direction-selective responses recorded in V2 thick stripes are independent of motion speed.