Brain and Vision
Purves et al., Chapter 12 (and bits of Chapters 11 and 24)
Projection to Brain
Fig. 12.1 p. 258
Overall Visual Projection
Eye -> LGN (Lateral geniculate nucleus, genu= knee, part of thalamus)
-> striate cortex
Temporal retinal field = nasal visual field stays ipsilateral at chiasm
Nasal retinal field = temporal visual field crosses to contralateral side
From LGN to striate cortex = area 17 = V1
Retinotopy (like somatotopic organization) is preserved
*Eye -> pretectum - pupil size (iris) and control of lens (accomodation)
Eye -> superior colliculus - eye and head movements (Chap. 19)
Eye -> hypothalamus - to regulate circadian rhythms (see, in chapter
*Fig. 12.2 p. 259
Pretectum -> Edinger-Westphal nucleus -> cranial nerve III->ciliary
ganglion ->parasympathetic fiber.
Note connection to both ipsilateral and contralateral sides after pretectum,
so pupillary reflex should be bilateral.
Kids, go ahead and try this.
Important test in neurology.
Fig. 12.13 A & B p. 268
Cells have center - surround receptive fields like ganglion cells
1, 4, 6 contralateral -- thus 2, 3, 5 ipsilateral
Fig. 12.15A p. 269
large and small retinal ganglion cells
Magnocellular - large receptive fields for processing movement - connect
to LGN 1 & 2
Parvocellular cells connect to layers 3, 4, 5, & 6 and process color,
also for acuity
DHHubel & TNWiesel, Receptive fields, binocular interaction and functional
architecture in the cat's visual cortex, JPhysio, 160, 106-154, 1962
TNWiesel, DHHubel & DMKLam, Autoradiographic demonstration of ocular
dominance columns in the monkey striate cortex by means of transneuronal
transport, Brain Res 79, 273-279, 1974 (see also J NIH Res, 5, 61-67, 1993)
DHHubel & TNWiesel, Brain mechanisms of vision, Scientific American
September 1979 (vol 241, #3), pp 150-162.
Tom Yin's home page, follow
links, Simple cell is a good video to show how work was done
Fig. 12.8 A & B p. 264
cat (monkey) looks at screen, cell responds best to line at angle
Striate cortex - physiology and anatomy
Hubel & Wiesel share 1981 Nobel
for "information processing in the visual sytem"
Fig. 12.11 p. 266
there are vertical columns of preferred angle (just like in somatosensory
presumably, to prefer line at angle, cell receives inputs from from alligned
center surround cells
these are called simple cells
complex cell - line at algle moving in direction
hypercomplex cells - line has end - corner
vertical electrode penetration gives cells with all the same preferred angle
an oblique penetration tracks different angles
Note that there are 6 layers of cells, IV has inputs from LGN
"Philosophical question" -- does processing get to more and more
levels of complexity until you find "grandmother cells" which
recognize, specifically, your grandmother's face?
Fig. (like 12.13 B & C) p. 268
experiment to determine ocular dominance columns (0.5 mm wide)
There are cortical cells with input from one eye, from the other eye, and,
in between, from both eyes.
Binocularly driven cells should be necessary for stereopsis, the kind of
depth perception which relies on the focussing of both eyes.
Fig. 12.14 p. 269
Apparently, cells can preferentially respond to disparity from fixation
Even higher order visual processing
With all that color processing in the LGN, it seemed odd how far the work
on the cortex got without any mention of color
Fig. 12.16A 272
V4 - color but not movement
MT (middle temporal) - direction of movement but not color
Fig. 12.18 p. 274
parietal stream - spatial vision
temporal stream - object recognition
This relates to Andrew Laguna S.J.'s presentation on the binding problem
Development of visual connections
Fig. 24.4 p. 545
If a radioactive amino acid is injected into one eye, labeled proteins cross
synapses at LGN and mark ocular dominance columns in cortex; this is detected
by microscopic autoradiography.
Binocular cells connect up correctly at first
Fig. 24.5 p. 546
Then there is a sensitive (critical) period in the first few months of life
during which patterned visual input from both eyes is necessary to maintain
binocular input to cortical cells.
Thus early visual defects like cataract or strabismus (cross-eyes or lazy
eye) need to be corrected right away.
Here are autoradiographs.
A of normal visual cortex, nd B after monocular deprivation from 2 weeks
to 18 months in monkey
*P Sinha Once blind and now they see, July 2013, 48-55. Blind from birth
Indian children get surgery, takes a while to learn to see. Hard to put
things together. SK was 29, had congenital aphakia (rare). "not particularly
thrilled" Motion helped
*BPeak Seeing is feeling (letter to the editor) Nov p 6. Book ­p; Pilgrim
at tinker creek (1974 by Annie Dillard) she quotes Space and Sight
(1932), patient could name a cube by feeling it but, after cataract surgery
could not name it if (s)he saw it
Exam questions from 2005 - 2011 relating to this outline
A stroke wipes out the connection of the pretectum to the contralateral
Edinger-Westphal nucleus but not to the ipsilateral one. How could you infer
this with a very simple non-invasive vision test on a cooperative subject?
There would still be a pupillary reflex but not in the contralateral eye
Say something about how the nasal portion of the retina projects to the
lateral geniculate nucleus
nasal retina connects to contralateral LGN's layers 1, 4, and 6.
An electrode is in a simple cell that fires action potentials vigorously
when stimulated with a thin, vertical stripe of light. How does it respond
to a thick stripe in the same location, and why does it react that way?
a lot less or not at all b/c the thick stripe also stimulates the inhibitory
Injection into one eye followed by a specialized histological technique
demonstrated a zebra-stripe pattern of ocular dominance columns in the visual
cortex. Answer either (1) What was injected in the eye? Or (2) What technique
was used for the visualization in the cortex?
a radioactive amino acid, audioradiography
You went home and tried what I suggested, shined a flashlight to one eye.
Alas, only one pupil constricts. Tell me a place where you have nerve damage.
has to be after the pretectum. maybe between the pretectum and the Edinger-Westphal
nucleus (one of two paths) or from there to the ciliary ganglion, to the
muscle (on one side)
If Hubel and Wiesel had looked for a grandmother cell instead of the cells
they identified (e.g. simple cell), why wouldn't they have gotten a Nobel
Their systematic approach was very productive, good thing they didn't start
looking for a needle in a haystack
How were the ocular dominance columns in normal and visually deprived animals
audioradiography, histological slices exposed photographic "film"
Occasionally I pointed to how uninteresting the wall was vs the perceptual
richness of the map on the wall. Say something about how the receptive field
organization in the lateral geniculate nucleus contributes to this difference.
center surround influences contrast
What is the most obvious thing that happens between the pretectum and the
Concerning layers in the lateral geniculate nucleus, answer either (1) What
is the main difference between layers 1, 4, & 6 vs 2, 3, & 5? Or
(2) What is the main difference between layers 1 & 2 vs 3 to 6?
1,4,6 contralateral, 1, 2 magnocellular
In the "movie" of Hubel and Wiesel's simple cell experiment, how
come a wide line of light projected right on target did not elicit firing
while a thin line, also accurately aimed, did?
wide hit inhibitory surround also
An oblique electrode track traverses several millimeters of the visual cortex.
What change do you notice about the receptive field properties of the firing
neurons you encounter?
one eye -> both -> other, (also angle of line)
A radioactive amino acid was injected into one eye. Say one of the several
cell biological events that must occur to give an autoradiogram of ocular
dominance columns. (I am not asking how to do autoradiography.)
is put into protein, is transported down axon, is transported across synapse,
transported down other axon
Why did I tell the story of geese following the Nobel prize winning ethologist
Konrad Lorenz in the context of the visual cortex?
sensitive (critical) period
How would you test whether a patient's contralateral connection from the
pretectum to the Edinger-Westphal nucleus were disrupted?
light to one eye would not consstrict the contralateral pupil
Specifically, what crossed the LGN (lateral geniculate nucleus) synaptic
cleft to allow Hubel to see the ocular dominance columns using autoradiography?
3H labeled protein
Where do the axons of the the temporal retina (nasal visual field) go at
to ipsilateral LGN
What is the word for the special type of "depth perception" mediated
by the parallax from focussing both eyes (and neural interactions of binocular
If a child were born with a congenital cataract in one eye, why should this
deserve immediate attention?
brain connections from that eye would vanish without patterened vision
Light stimulation to one eye activates that eye's optic nerve. By what mechanism
would there be efferent output to the iris from both occulomotor nerves?
connection to one pretuctum goes bilaterally to Edinger-Westphal nuclei
The inputs from the two eyes to the lateral geniculate nucleus do not mix.
In what manner are they kept separate?
they go to different layers, contralateral to 1, 4, & 6, ipsilateral
to 2, 3, & 5
A thin bar of light made the simple cell fire quickly. Why did a wider bar
not do likewise?
Because the wider bar also hit the inhibitory areas in the receptive field
of that cell
What technique did Hubel and Wiesel use to get that picture of the visual
cortex with stripes?
Autoradiography, or, inject radioactive amino acid into one eye and observe
the protein transported transynaptically from ganglion cell across LGN to
As an electrode is advanced obliquely across columns in the visual cortex,
One could say preferred eye of input or one could say preferred angle of
Why did Hubel and Wiesel feed their microelectrode amplifier into a loud
easy to judge firing rate by the sound
Why did a wide line centered on the simple cell's receptive field elicit
less of a response than a narrow line?
even though it stimulates the excitatory receptive field, it also stimulates
the surrounding inhibitory ones
While an electrode is advanced obliquely through the cat's visual cortex,
first the left eye predominates, then the right eye. What else has been
changing during that advancement?
When is the critical (sensitive) period for development of binocular connections
in the cat visual cortex?
birth to 2 & 1/2 mo
When autoradiography was used to demonstrate ocular dominance columns, how
did the film (photographic emulsion) get exposed?
radioactivity (in cortex protein) exposed film in the dark
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