Download Signal Detection Theory

Visual Learning
Instructor: Arnold Glass
Visual Processing
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Millions of computations are performed on
the light patterns that fall on the retina before
we see images consciously.
Much of what goes on in the brain during
vision is unconscious (prior to awareness).
Processing begins with Sensory
Registration, as shown in the next slide.
The Sensory Registration
Stage Parietal Primary visual
Cortex
Midbrain (eye
movements)
Pulvinar
Thalamus nucleus
Lateral
geniculate
nucleus
Optic tract divides into 3 paths:
Retina
Ganglion cells
bipolar cells
photoreceptors
Superior
Colliculus
Visual Pathways
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As shown in the previous slide, after
sensory registration the visual pathway
divides into:
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The eye-movement pathway (superior
collicus)
How pathway for all other movements
(parietal cortex)
What pathway (occipital cortex)
produces visual perception
Visual Pathways

As shown in the previous slide, after
sensory registration the visual pathway
divides into:

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The eye-movement pathway (superior
collicus)
How pathway for all other movements
(parietal cortex)
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Damage to how pathway causes visual apraxia.
What pathway (occipital cortex)
Visual Perception (What
Pathway)
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There are multiple levels of analysis of
the visual input involving many levels of
representation, as shown in the next
slide.
Stages of Visual Perception
Shape construction
Compare with memory
Select plausible surface representations
Integrate into 3D object representation
Feature analysis
Texture segmentation
Binocular representation
Compute 3D representation
Sensory Registration
Compute 3D representation
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One early step is the comparison of the
disparities between the retinal images to
construct a single 3D image.
Another early step is combining features into
textures that ultimately define forms.
Stages of Visual Perception
Shape construction
Compare with memory
Select plausible surface representations
Integrate into 3D object representation
Feature analysis
Texture segmentation
Binocular representation
Compute 3D representation
Sensory Registration
Select 3D representation
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Often more than one 3D representation is
consistent with the sensory input. In this
case, each representation is compared with
memory and the most plausible is selected.
Since the visual system relies on memory to
select a single probable 3D representation,
learning affects perception.
Upright and Inverted
Moonscape
Towers
Barns and huts
Types of Visual
Agnosia
Recognition
Mesial
Temporal
Subcortex
Inability
to access
memory
associative
agnosia
Surrounding
Visual Cortex
Top Down
Perceptual
Processing
Occipital
Cortex
Bottom up
Perceptual
Processing
LGN of
Thalamus
Retina
Inability
to integrate
Features
apperceptive
Agnosia or
simultagnosia