The processing of kinetic contours in the brain.
This work investigates whether the brain assigns special cortical areas for the processing of kinetic contours. In human imaging experiments, we compared the brain activity produced in the so-called 'kinetic occipital' area ('KO') when humans perceive shapes generated from kinetic boundaries or from equiluminant colors. 'KO' was activated whenever subjects perceived shapes, no matter how they were derived; it is therefore not specialized for the processing of kinetic contours. The application of independent component analysis (ICA) to imaging data obtained when subjects viewed 22 min of an action movie showed that the time course of activity in 'KO' correlates better with activity in area V3 than with activity in two adjacent areas, V5 and LO. We thus consider 'KO' to be part of the V3 family of areas, and use the terminology of Smith et al. (J Neurosci 18:3816-3830, 1998), to refer to it as area V3B. Recordings from orientation-selective cells in the macaque V3 complex show that the great majority have the same orientational specificity when tested with oriented lines generated from kinetic stimuli or from luminance differences. We conclude that there is no present evidence for a visual area specialized for the processing of kinetic contours in the primate visual brain.