NEUR 0010 - Chapter 10 Flashcards
What part of the visual field crosses?
The part that goes to either nasal retina
What visual hemispheres are viewed by what hemispheres?
LVF entirely viewed by RH; RVF entirely viewed by LH
Which pathway mediates conscious visual perception?
From eye to LGN to visual cortex through the optic radiation
What do ganglion projections to the hypothalamus do?
Circadian rhythms, etc.
What do ganglion projections to the pretectum do?
Control pupil size, some eye movements
What do ganglion projections to the superior colliculus do?
Commands eye and head movements to bring the light stimulus into space on the fovea to better focus on it
How many layers are there to the LGN?
Six, numbered 1 to 6, with 1 being the most ventral and 6 being the most dorsal
The right and left LGNs receive input from which VFs? Which retina?
Right LGN receives input from LVF (left temporal, right nasal); left LGN receives input from RVF (right temporal, left nasal)
Which LGN layers are parvo vs magno?
1-2 are magno, 3-6 are parvo
What is the order of ipsi/contralateral input to the LGN layers, for VF and for retina, from 1 to 6?
Retina: CIICIC; VF: entirely C (right LGN receives entirely LVF: left nasal, right temporal)
What is the majority of input to the LGN?
80% from visual cortex, not the eyes
What fissure does the striate cortex surround?
Calcarine fissure
What is retinotopy?
Neighboring cells in the retina feed information to respectively neighboring cells in the cortex; spatial mapping
How accurately does the retinotopic map represent the visual field? How so?
Not particularly: the central few degrees are very magnified and thus have a disproportionate amount of cortical space
How many cells does a discrete point of light activate in the striate cortex? What does this say about retinotopy?
Many many! A point of light on the retina activates many cortical neurons, because of overlapping RFs
What are the characteristics of Layer I of the striate cortex?
Right underneath the pia mater; no neurons, just axons and dendrites of cells from other layers
There are actually 9 striate cortex layers. How does that come from 6?
Layer 4: A, B, C-alpha, C-beta
What are the two principal types of cells in the striate cortex layers?
Spiny stellate, pyramidal
Where are spiny stellate cells found?
Layers 4C-a and 4C-b of the striate cortex
Where are pyramidal cells found in the striate cortex?
Any of the layers except 4C-a/b and Layer 1
Which kind of cell, spiny stellate or pyramidal, extends beyond the striate cortex to make connections?
Pyramidal: spiny stellate stays local
What is the third type of cell found in the striate cortex?
Inhibitory: local connections only
What are the inputs to Layer 4C of the striate cortex?
4C-a input from LGN Magno, 4C-b from LGN Parvo
LGN magno and parvo connect to which layer of the striate cortex?
4C-a, 4C-b
LGN konio connects to which layer of the striate cortex?
Layers 2 and 3
What are ocular dominance columns?
Differing zebra stripes of LE vs RE input to the striate cotex’s Layer 4C
What are radial connections in the striate cortex?
When the intracortical connections run perpendicular to the cortex layers
What are horizontal connections in the striate cortex?
When the intracortical connections run parallel to the cortical layers by collateral branches
Where are horizontal connections in the striate cortex?
Layer 3
Where in the striate cortex is the first time where LE and RE input mix?
Layer 4B
What is the difference in input quality/type between striate cortex 4C and 4B?
4C in monocular, 4B is binocular (LE and RE mix)
Are striate cortex Layers 2/3 monocular or binocular?
Binocular
Layers 4C-a and 4C-b project their magno/parvo information to which layers of the striate cortex?
4C-a (magno) projects to 4B, and 4C-b (parvo) projects to 3
Which striate cortex layers have output to other cortical areas?
2/3, 4B
What striate cortex layer has output to the superior colliculus/pons?
5
What striate cortex layer has output to the LGN?
6
What striate cortex layers have cytochrome oxidase blobs?
2,3,5,6
What do cytochrome oxidase blobs do?
Receive direct LGN input from koniocellular layers, receive input from magno/parvocellular layers in striate cortex 4C
Where are cytochrome oxidase blobs located?
Layers 2,3,5,6; in Layer 3, centered over ocular dominance columns
What does it mean that the RFs of neurons in Later 4C (a,b) are similar to the RFs of magno/parvo cells in the LGN?
Generally small, monocular, center-surround
What is the difference in sensitivity between 4C-a and 4C-b RFs?
4C-a is not sensitive to color; 4C-b is sensitive to color
What feature of Layer 4C of the striate cortex accounts for ocular dominance columns?
Monocular afferent input is usually lumped together
What does it mean that super-4C layers have binocular RFs?
Once the output of Layer 4C branches out, creates binocularity; so each neuron from there has a RF in the ipsi and contralateral eye
What happens to ocular dominance columns once your get superficial to Layer 4C?
Fuzzier: zones that more strongly respond to one eye than the other
Which layers are orientation selective in the striate cortex?
Most layers except 4C
What is an orientation column?
The fact that for orientation-selective neurons in one layer, the same orientation selectivity extends radially down the whole cortex in that column
What are orientation-selection neurons important for?
Object shape recognition; “what” pathway (temporal, ventral)
Direction selectivity is a hallmark of which types of cells?
LGN magnocellular-input neurons
What are Hubel and Weisel’s “simple cells?”
Cells where cortical neurons get converging input from 3+ LGN cells with RFs along an axis; segregations of ON/OFF regions
Simple cells are what kind of selective?
Orientation selective
What are Hubel and Weisel’s “complex cells?”
No distinct ON/OFF regions; give ON and OFF responses to stimuli throughout RF
What is the general visual response of interblob cells (outside Layer 4)?
Binocular, orientation selective, direction selective; can be simple/complex; not wavelength sensitive
What is the general visual response of blob cells (outside Layer4)?
Monocular, not orientation/direction selective; wavelength sensitive
What is the shape of blob cell RFs?
Circular
Which cells contain most of the color-sensitive neurons outside of Layer 4C?
Blob cells!
What is the magnocellular pathway?
M-type ganglion cells in retina -TO- magno layers of LGN -TO- layer 4C-a of striate cortex -TO- layer 4B of striate cortex
What are the characteristics of Layer 4B pyramidal cells of the magnocellular pathway?
Binocular, simple/complex RFs, orientation/direction selective, color insensitive
What is the magnocellular pathway used for?
Object motion and guidance of motor actions
What is the parvo-interblob pathway?
P-type ganglion cells in retina -TO- parvo layers of LGN -TO_ layer 4C-b of striate cortex -TO- layer 2/3 interblob regions
What are the characteristics of Layer 2/3 interblob cells of the parvo-interblob pathway?
Binocular, simple/complex RFs; orientation selective; direction/wavelength insensitive
What is the parvo-interblob pathway used for?
Analysis of fine object shape
What is the blob pathway?
nonM-nonP ganglion cells in retina -TO- konio layers of LGN -TO- blobs in layer 2/3 of striate cortex directly!
What are the characteristics of blob pathway cells?
Convergence of P/M/K input; monocular; center-surround color-opponent RFs; orientation/direction insensitive; color sensitive
What is the blob pathway used for?
Analysis of object color
What is the dorsal stream for?
Analysis of visual motion; visual control of action
What is the ventral stream for?
Perception of visual world, recognition of objects
Dorsal vs ventral streams are associated with which pathways?
Dorsal is M, Ventral is P-inter/Blob
What is area MT?
Dorsal stream: specialized processing of object motion (direction-selectivity)
How is cortical area arranged in area MT?
Direction-selective columns
What is area V4?
Ventral stream: shape/color perception
What is area IT?
Ventral stream: face perception, fusiform gyrus
