Robust form perception and underlying neuronal mechanisms require generalized
representation of object boundaries, independent of how they are defined.
One visual ability essential for form perception is reconstruction of contours
absent from the retinal image. Here we show that barn owls perceive subjective
contours defined by grating gaps and phase-shifted abutting gratings. Moreover,
single-neuron recordings from visual forebrain (visual Wulst) of awake, behaving
birds revealed a high proportion of neurons signaling such subjective contours,
independent of local stimulus attributes. These data suggest that the visual
Wulst is important in contour-based form perception and exhibits a functional
complexity analogous to mammalian extrastriate cortex.
