Cao A; Schiller PH
Visual Neuroscience, 2003,
20:1, 77-84.
Abstract
Relative motion information, especially relative speed between different input
patterns, is required for solving many complex tasks of the visual system, such
as depth perception by motion parallax and motion-induced figure/ground segmentation.
However, little is known about the neural substrate for processing relative
speed information. To explore the neural mechanisms for relative speed, we recorded
single-unit responses to relative motion in the primary visual cortex (area
VI) of rhesus monkeys while presenting sets of random-dot arrays moving at different
speeds. We found that most VI neurons were sensitive to the existence of a discontinuity
in speed, that is, they showed higher responses when relative motion was presented
compared to homogenous field motion. Seventy percent of the neurons in our sample
responded predominantly to relative rather than to absolute speed. Relative
speed tuning curves were similar at different center-surround velocity combinations.
These relative motion-sensitive neurons in macaque area VI probably contribute
to figure/ground segmentation and motion discontinuity detection..