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Chapter 7

Chapter 7- big notes

Course Code
Steve Joordens

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PSYA01: Chapter 7 Notes from the Textbook
Brain Mechanisms of Visual Perception
oPerception: detection of the more complex properties of a stimulus, including its
location and nature; involves learning
ex. seeing the colour red is sensation, seeing a red apple is perception
osensation takes place in the eye (for example) and perception takes place in the
oneurons in the primary visual cortex send visual information to two successive
levels of the visual association cortex
Primary Visual Cortex
ogeography of the visual field is retained in the primary visual cortex
the surface of the retina ismapped” on the surface of the primary
visual cortex
however, the map on the brain is distorted, largest area is the centre of
the visual field
oeachtile” (called module) of the map consists of a block of tissue with around
150 000 neurons
oall of the neurons within a module receive information from the same small
region of the retina, meaning that it receives information from a small region of the
visual field
oneural circuits within each module analyzed various characteristics of their own
particular part of the visual field
oReceptive Field: that portion of the visual field in which the presentation of
visual stimuli will produce an alteration in the firing rate of a particular neuron
circuits detect :lines for orientation (or angle), thickness of lines,
movement and direction, colours
obecause each module in the primary visual cortex receives information about
only a restricted area of the visual field, the information must be combined
somehow for perception to take place – this combination takes place in the visual
association cortex
Visual Association Cortex (vac)
ohas two levels
ofirst level: has subdivisions, each of which contain a map of the visual scene,
surrounds the primary visual cortex
oeach subdivision receives info from different types of neural circuits within
modules of the primary visual cortex (ex. one subdivision is for line orientation,
another is for colour, etc.)
otwo regions in the second level of vac put together info gathered and processed
by subdivisions of first level – info about shape, colour, lines are combined
osecond level: parietal lobe and lower temporal lobe

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oin parietal lobe, second level is responsible for perception of location of objects
– integrates info from first level of vac with info from motor system and body
Effects of Brain Damage on Visual Perception
odamage to primary visual cortex causes blindness in some portion of the visual
field, depending on where the damage is
odamage to vac does not disrupt the person’s ability to see fine details, but it does
produce varying amounts of difficulty in perceiving shapes and objects or in
perceiving particular visual characteristics
oAchromatopsia: inability to discriminate among different hues; caused by
damage to the vac
odamage to vac can also make it difficult for a person to keep track of moving
oif vac. in the parietal lobe is damaged, person will experience Balint’s
Syndrome: a syndrome in which the person has difficulty in perceiving the location
of objects and reaching for them under visual guidance
odamage to vac in temporal lobe can disrupt the ability to recognize objects
oVisual Agnosia: the inability of a person who is not blind to recognize the
identity of an object visually; caused by damage to the vac
oProsopagnosia: a form of visual agnosia characterized by difficulty in
recognition of people’s faces; caused by damage to vac
Perception of Form
Figure and Ground
owe classify most of what we see as either object or background
oFigure: a visual stimulus that is perceived as a self-contained object
oGround: a visual stimulus that is perceived as a formless background against
which objects are seen
oexistence of a boundary defines a figure
Organization of Elements: gestalt Laws of Grouping
oGestalt Psychology: a branch of psychology that asserts that the perception of
objects is produced by particular configurations of the elements of stimuli
operception as a whole is more than the sum of its parts
owhat we see depends on the relationships of these elements to one another
othe real world presents us with objects partly obscured by other objects and with
oelements in a visual scene can combine in many ways to produce different
forms: laws of groupings
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