4. Vision - Organization of V1 Flashcards
the primary visual cortex is functionally organized into a:
retinotopic map
adjacent points in the visual field are represented by:
adjacent neurons in V1
true or false: visual information from the fovea is magnified in the visual cortex
true
signals from the fovea account for ____% of the visual cortex even though it takes up ____% of the retina
8-10%, 0.1%
upper points in the visual field are represented in the:
lower part of the visual cortex
organized regions of neurons in the visual cortex that are excited by visual line stimuli of varying angles
orientation columns
stripes of neurons in the visual cortex of certain mammals (including humans) that respond preferentially to input from one eye or the other
ocular dominance columns
what does it mean if a column of cells is “ipsolateral dominant”?
the column responds more to signals from the ipsolateral eye than the contralateral eye
almost all neurons in the visual cortex are:
binocular
a model for the organization of the visual cortex which involves orientation columns being arranged in slices and ocular dominance columns being divided in two (right and left)
the “ice tray” model
according to the “ice tray” model, the orientation columns were arranged like slices of bread, where each slice represented:
a different orientation preferance
within the ice cube tray, colour was represented by:
randomly dispersed colour blobs
areas of increased blood flow which rotate (clockwise or counterclockwise) as the orientation of a stimulus changes
pinwheel orientation columns
how do ocular dominance columns fit in the “pinwheel” model?
they bisect the pinwheel
which is the correct model for the functional organization of the primary visual cortex: the “ice tray” model or the “pinwheel” model
the pinwheel model
do all visual species have orientation columns?
no, some have orientation cells sporadically placed in the cortex (salt and pepper model)
why is it that some animals don’t have pinwheels?
animals like rodents have poorly developed visual cortexes and retinas (aka fovea), and rely heavily on their whiskers
what is a good indicator that an animal will have pinwheel organization in the primary visual cortex?
having a more developed fovea
do pinhweels apply to colour?
yes
connect areas of similar orientation within the primary visual cortex
horizontal connections
how do we test for horizontal connections in the primary visual cortex?
anterograde tracing
what is the proposed purpose of the horizontal connections?
thought to take the parts of an area and make a whole (ex: pac man things arranged to look like a square even though there’s no lines to connect them)
