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Chapter 4

PSYC 2390 Chapter Notes - Chapter 4: Retinotopy, Two-Streams Hypothesis, Prosopagnosia


Department
Psychology
Course Code
PSYC 2390
Professor
Lana Trick
Chapter
4

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Sunday, February 18, 2018
Chapter 4: Cortical Organization
Introduction
spatial organization - how different locations in the environment and on the retina are
represented by activity at specific locations in the visual cortex
Spatial Organization In The Visual Cortex
the neural map on the striate cortex (area V1)
points of the retinal image cause activity in the cortex (spatially), and the locations
on the cortex correspond to locations on there retina
retinotopic map - electronic map of the retina on the cortex
-means that 2 points that are close together on an object and on the retina will
activate neutrons that are close together in the brain
cortical magnification - more space is devoted to areas of the retina near the fovea,
and the representation on the cortex becomes distorted in order to allow more space
to locations near the fovea than to the peripheral retina
-this is why some points may be the same distance apart on the retina and not
the cortex
-cortical magnification factor - the small area of the fovea (0.01%) is represented
by a large area on the visual cortex (8-10%)
-when you look at a scene, the information of the part of the scene you are
looking at takes up a larger space on your cortex than an area of equal size that
is off to the side, which is why the fovea has more space, which translates into
better detail vision rather than size
brain imaging
-magnetic resonance imaging (MRI) - made it possible to create images of
structures within the brain
-functional magnetic resonance imaging (fMRI) - enables us to determine how
various types of cognition activate different areas of the brain
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Sunday, February 18, 2018
-fMRI looks at blood flow and how it increases when areas of the brain are
activated
-determines activity of areas of the brain by detecting changes in the magnetic
response of the hemoglobin
-converted into colour displays to show increases and decreases in activity of the
areas
the cortex is organized in columns
location and orientation columns
-striate cortex is organized into location columns that are perpendicular to the
surface of the cortex so that all of the neurons within a location column have their
receptive fields at the same location on the retina
-the cortex is also organized in orientation columns, with each column containing
cells that respond best to a particular orientation, and that adjacent orientation
columns have cells with slightly different preferred orientations
one location column: many orientation columns
-one location column (1mm) serves one location on the retina, as all neurons in
column have receptive fields at same place on retina, and contains neurons that
respond to all possible orientations, so each orientation within that area will
cause neurons to fire (“hypercolumn” receives information about all possible
orientations that fall within a small area of the retina)
how do orientation-sensitive neurons respond to a scene?
the cortical representation of a stimulus doesn't have to resemble the stimulus, just
has to contain information that represents the stimulus
tiling - when each part of the scene represents an area that sends information to one
location column, and working together these columns cover the entire visual field
-visual field served by adjacent (often overlapping) location columns
Pathways For What, Where, And How
streams for information about what and where
ablation/lesioning - the destruction or removal of tissue in the nervous system
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