Please enable JavaScript.
Coggle requires JavaScript to display documents.
Visual Pathways - Coggle Diagram
Visual Pathways
Parallel Pathways
within V1
hypothetical model
three pathways
magnocellular pathway
begins with M-type ganglion cells of the retina
send axons to the magnocellular layers of the LGN
project to layer IVCα of striate cortex
projects to layer IVB
1 more item...
parvo-interblob pathway
begins with P-type ganglion cells of the retina
project to the parvocellular layers of the LGN
sends axons to layer IVCβ of striate cortex
projects to layer II and III interblob regions
1 more item...
blob pathway
receives input from the nonM-nonP ganglion cells
project to the koniocellular layers of the LGN
projects directly to the cytochrome oxidase blobs in layers II and III
Many neurons in the blobs are color selective, so they might be involved in the analysis of object color.
simple version of the story; the reality is more complicated.
pathways not strictly segregated and do not have entirely unique receptive field properties
Perception
Perhaps the brain uses a “division of labor” principle for perception.
Within a given cortical area, many broadly tuned cells may serve to represent features of objects.
At a bigger scale, a group of cortical areas may contribute to perception, some dealing more with color or form, others more with motion.
two large-scale extrastriate cortical streams
dorsal stream :runner:
from the striate cortex toward the parietal lobe
involved in
analysis of visual motion and the visual control of action
progression of areas
V1 → V2 → V3
Area MT / V5
pecialized processing of object motion
receives retinotopically organized input from a number of other cortical areas (e.g. V2 and V3)
and
is directly innervated by cells in layer IVB of the striate cortex.
Area MT is most notable for the fact that almost all the cells are direction selective, unlike areas earlier in the dorsal stream or anywhere in the ventral stream.
This cortical area is arranged into direction-of-motion columns analogous to the orientation columns in V1.
in the parietal lobe
e.g. medial superior temporal (MST) area
cells selective for linear motion (as in MT), radial motion (either in- ward or outward from a central point), and circular motion (either clock- wise or counterclockwise)
ventral stream :girl:
toward the temporal lobe
involved in
perception of the visual world (visual attributes and the recognition of objects
progression of areas
V1 → V2 → V3
Area V4
receives input from the blob and interblob regions of the striate cortex via a relay in V2.
have larger receptive fields than cells in the striate cortex, and many of the cells are both orientation selective and color selective.
appears to be important for both
shape
perception and
color
perception.
clinical e.g. achromatopsia
loss of color vision despite the presence of normal functional cones
2 more items...
Area IT
area in the inferior temporal lobe
the farthest extent of visual processing in the ventral stream.
Output from area IT is sent to temporal lobe structures involved in learning and memory
IT itself may be important for both visual perception and visual memory.
1 more item...
What are the pathways in V1 and outside V1 that allow us to visualize the world?