- Vision 381
Cortical Visual Processing
■ Th e ventral stream comprises the “what,” object
recognition pathway (or P pathway).
■ Th e dorsal stream comprises the “where,” spatial
localization (or M pathway).
■ Th e cone photoreceptors are responsible for color
detection and excite parvocellular ganglion cells of
the “what” pathway.
■ Th e rod photoreceptors are responsible for motion
detection and excite magnocellular ganglion cells of
the “where” pathway.
■ Th e primary visual cortex in each hemisphere
encodes the visual fi eld from the opposite half of the
world.
■ Th e secondary visual cortex processes illusory
boundaries: contours that cannot actually be
visualized but that are implied by the context of a
larger scene.
■ Area V4 is the color processing area; it demonstrates
color constancy.
■ Th e lateral occipital complex responds
disproportionately strongly for object recognition
and displays perceptual constancy.
■ Th e fusiform face area is the most well-studied area
for facial processing.
■ Non-face body parts are processed separate from
faces: most notably, in the extrastriate body area in
the lateral occipitotemporal cortex.
■ Th e parahippocampal place area processes places:
environmental scenes and buildings.
■ Th e motion-processing center lies at the occipital-
temporal-parietal junction.
■ Th e parietal lobes contain numerous visual cortical
areas dedicated to the processing of spatial awareness,
collectively called the “parietal dorsal stream area,”
which comprises the “where” pathway.
■ High-level processing of vision allows for the
preservation of depth perception in the setting of
monocular (one-eye) vision.