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BHS 140.2 – Vision Science II
Notetaker: Mallory McLaughlin
Date: 04/22/2013
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Post V1- continued
Page 11- She added things to explanation from 4/18, but I’ve included all information here for the sake of
being complete. What she added today is underlined.

The following was discovered by staining with
cytochrome oxidase


V1- consists of interblobs and blobs
o
Interblobs get input from M and P cell pathways
o
Blobs get input from K cell pathways only
V2-consists of thick, pale, and thin stripes
o
Thick- encodes depth perception via retinal disparity. The interblob pathway from V1
feeds into them

o
Pale- encodes orientation. The interblob pathway from V1 feeds into them
o
Thin- encodes color. The blob pathway from V1 feeds into them
V4 is a color area.
o
Overall, V4 indirectly receives input from M,P, and K cell pathways that were
recombined into pale and thin stripes. It also directly receives input from M cell pathway
from layer IVCalpha of V1

V5 (MT) is a motion area
o
Overall, it receives input from M and P cell pathways that were recombined into thick
stripes. It also receives direct M cell pathway input from IVCalpha of V1.

If a patient has bilateral damage to V4, they will have cerebral achomatopsia. This an acquired,
also known as cortical, color vision defect

If they just have monocular damage to V4, they might not notice. This defect is variable and more
difficult to classify.

The whole point of this picture is to illustrate that M, P, and K cell pathways are no longer
segregated post-V1. They are jumbled and recombined for specific purposes.
Ventral Pathway
Anatomy of the Ventral Pathway
o
Function- “what” pathway. It’s not just detection of objects, but is necessary for detection
(perception), recognition, and memory of an object. It underlies “conscious” perception.
o
The pathway’s job is to extract the enduring characteristics of an object that can be maintained across
different viewing conditions. This is called a perceptual constancy
BHS 140.2 – Vision Science II
Notetaker: Mallory McLaughlin

Date: 04/22/2013
Page2
Ex- When you hold a piece of paper parallel to your face, it projects a rectangular image on
your retina. When you put it down on the table, it projects a trapezoidal image on your retina,
but we still know that it’s rectangular. The output of the ventral system is how we know that
it’s the same object even though the image is different, because it extracted the enduring
characteristic of rectangular shape.

Ex- Contrast is an enduring (invariant) characteristic extracted by the ventral pathway. If you
take your notes outside, they look the same as they did inside even though the luminance of
the black letters outside is greater than the luminance of the white paper inside. We’d think
that the black letters would look white if the luminance was greater than the white paper, but
it doesn’t. This is due to the perceptual constancy of the ventral pathway.
o
Pathway
Information from V1 is funneled through V2 and V4 to get down to the inferior temporal
cortex.

LGN -> V1 -> V2 ->V4 ->TEO ->TE (add those arrows in your notes) These are the
ones we need to memorize

Ventral pathway gives rise to conscious perception, and dorsal pathway is
unconscious perception. If your V1 is destroyed, you will not have conscious visual
perception, but that doesn’t mean you are blind. You will still have intact
unconscious perception from the dorsal pathway. This will be explained more
tomorrow.

Illustration on page 14 shows you WHERE these regions are located in the brain
with a transparent view

You can see optic radiations emanating from
the LGN

Not all of the vision areas are in the occipital
lobe, some are in temporal or parietal lobe as
well
o
V1 is at the posterior pole spreading
medially
o
V2 is symmetrical about V1
o
V3 and V3A are symmetrical about V2
o
After V4, it loses is symmetry. V4 is barely visible on the
outside of the brain
BHS 140.2 – Vision Science II
Notetaker: Mallory McLaughlin
Date: 04/22/2013
Page3
o
If there are 30+ different regions, they can’t all be in the
occipital lobe

The sagittal section shows a medial view
o
V1, V2, V3, and V3a also extend inside the cortex
o
V4 is mostly internal**. Only see it if you look inside of the
brain

TEO is Temporal Occipital Region and TE is the Anterior Inferior Temporal
Cortex are both in the temporal lobe

TE is the end of “exclusively visual processing” but it’s not the end of
the pathway. It is combined with other types of information, motor etc
Characteristics of the Ventral Pathway distinct from the Dorsal Pathway
1. The ventral pathway is so concerned about detection, recognition, and memory, that the location
of the object is lost. The technical way to say this is “there is increasingly less retinotopic
organization” in post-V1 areas.
a. “Retinotopic organization” means that parts of the visual world that are spatially adjacent
to each other are processed by neurons that are spatial adjacent
b. However, in this pathway, two adjacent neurons in the ventral pathway might be
processing parts of the visual world that are very far away from each other.
c. The receptive area for neurons in TE is as wide as the visual field!
2. Neurons in the pathway respond to increasingly more complex stimuli
a. Retina and LGN neurons respond well to edges that are defined by luminance which can
be described as a certain contrast
b. V1 neurons will also respond to edges, but it’s more complicated. They will respond to
edges defined by:
i. Texture changes
ii. Color changes
iii. Movement
3. Post V1 neurons can respond to specific things. The examples
chosen were Face Detectors and Place Detectors
a. Face Detectors:
i. In the picture to the right, a monkey was shown
different stimuli and the response of his “face
detecting” neurons was recorded.
BHS 140.2 – Vision Science II
Notetaker: Mallory McLaughlin
Date: 04/22/2013
Page4
ii. If the monkey was shown a face of another monkey or a human, there was a
vigorous response. Even if it was just a picture of the face, the response was
strong.
iii. If a caricature of a face was shown, the response was moderately decreased. If
the face was missing the eyes, the response was significantly decreased. If the
features were jumbled, there was almost no response.
iv. As controls, if a hand was shown, there was no response. If a random picture was
shown, there was no response
v. The point- neuron doesn’t recognize the face unless all of the features are
present and correctly organized!
b. Place detectors- respond robustly when an image is given that encode a place. They do
not respond to faces at all
i. They recorded MRI’s- remember that you’re looking at a horizontal cut through
their brain and you’re looking from their feet
ii. The left MRI is the inferior horizontal cut because you can see the cerebellum
and the frontal lobe is very small. It shows the fusiform face area highlighted in
yellow that is more lateral.
iii. The right MRI is the more superior horizontal cut. It shows the parahippocampal
place area highlighted in yellow that is more medial
iv. Realize that the fusiform face area and parahippocampal place are in the temporal
lobe
1. Hippocampal gyrus is most medial, fusiform is more lateral, and inferior
temporal gyrus is more medial yet
2. Fusiform gyrus is aka “occipital-temporal gyrus” in our neuroanatomy
course
v. The face area lights up when you show faces and the place area lights up when
you show places