chapter 13 Flashcards
Occipital lobe is
posterior within the brain, and its major function is vision
Occipital lobe contains many distinct
visual areas
visual areas extend into the
temporal and parietal lobes
Primary visual cortex (V1) surrounds the
calcarine sulcus and contains distinct layers and sublayers
Within V1, “blobs”
process color information
the cells between the blobs process
form and motion
Thin stripes are involved in
color perception
Thick stripes process
form information
Pale stripes are involved in
motion perception
Color perception enhances our ability to
detect form and motion
Visual processing starts in
V1 and projects to all major visual areas
V2 is the
secondary processing location, and it also projects onward to major visual areas
V1 projects through V2 projects to
Dorsal stream, Ventral stream, STS stream
STS stream
object perception and motion perception
Ventral stream
object perception and motion perception
Dorsal stream
visual guidance of movement
V1 and V2 seem to be heterogeneous general areas processing
all types of visual information
Higher visual areas are more
specialized but can still integrate information from multiple aspects of vision
V3
processes dynamic form, or the shapes of objects in motion
V4
predominantly processes color information
V5
involved in motion processing; also known as MT
Damage to these higher visual areas results in
deficits specific to the functions of those areas
People with damage to V1 report being
blind, but smaller projections from subcortical areas to higher visual areas provide some limited vision
visual ventral pathway contains two parts,
one on the lateral surface and the other on the ventral surface of the temporal lobe
Visual streams project to many higher visual areas throughout the
temporal, parietal, and frontal lobes, and these areas seem to have specific functions, although they interact
The lateral ventral pathway may be related to
language and tool use, so may be unique to humans
Lateral occipital region
object analysis
fusiform face area
face analysis
Extrastriate body area
body analysis
fusiform body area
body analysis
superior temporal sulcus
analysis of biological motion
superior temporal sulcus (posterior)
moving body analysis
Parahipocampal place area
analysis of landmarks
ventral stream regions (7)
LO, FFA, EBA, FBA, STS, STSp, PPA
dorsal stream regions
LIP, AIP, VIP, PRR, IPS
lateral intraparietal sulcus
voluntary eye movement
anterior intraparietal sulcus
object direct grasping
ventral intraparietal sulcus
visuomotor guidance
parietal reach region
visually guided reach
intraparietal sulcus
object-direct action
Dorsal stream regions (5)
LIP, AIP, VIP, PRR, IPS
Visual processing is necessary to direct
specific movements
directing specific movements can be done
with or without attention and awareness
Processing visual information about a moving target in order to catch it requires
the interaction of multiple visual areas, largely in the parietal lobe and part of the dorsal stream
When you look at an object, your visual system focuses on
only part of that object
When looking at a face, an observer focuses on the
eyes and mouth, particularly in the left visual field
This bias to the left visual field seems to be specific for viewing
Faces
When a subject performs a mental rotation task, the task is often accompanied by
eye movements
egocentric space
object in relation to the observer
allocentric space
objects in relation to each other
Vision’s primary function is to guide
movement, not to recognize objects
Information for visually guided movement projects from
V1 to parietal areas over the dorsal stream
Patient with damage to the lateral occipital area could
shape their hand to grasp an object they could not consciously see
Patients with dorsal stream damage can
see objects but cannot accurately reach for them
Dorsal stream provides
real-time visual control of action
Posterior parietal visual neurons are active only when the brain is
acting on visual information
Information about shape, movement, and location is sent to the
parietal lobe over different pathways
Parietal-cortex lesions that impact visual areas are typically characterized as
visuospatial or visuomotor
When asked to detect motion, area
V5 showed increased activity
When asked to detect color, area
V4 showed activity
Left side of each retina projects to the
left hemisphere
and right side of each retina projects to the
right hemisphere
Information from both eyes about a particular location in space is combined in
V1
If a visual disturbance affects both eyes, the disturbance must be in
V1
Visual disturbances that affect information from only one eye must occur at
the level of the eye, the retina, or the optic nerve
Damage to the visual cortex typically spares information from the
central part of the visual field (macular sparing)
Reason for macular sparing
could be because the region of the visual cortex corresponding to macular vision receives blood from multiple cerebral arteries, making a stroke in that area less likely
Scotomas
small blind spots that are often unnoticed because the eyes are constantly moving and the brain fills in the blind spots with information from the previous position of the eyes
A complete lesion of area V1 in the left hemisphere results in
hemianopia affecting the right visual field
A large lesion of the lower lip of the calcarine fissure produces a
quadrantanopia that affects most of the upper-right visual quadrant
A smaller lesion of the lower lip of the calcarine fissure results in a
smaller injury, a scotoma
Cortical blindness occurs when a patient has no
conscious awareness of visual stimuli but can accurately indicate locations, directions, forms, or colors of the stimuli
Following damage to area V5, patient was unable to
detect motion
Following damage to area V5, patient was unable to detect motion
Pouring fluids was difficult because she could not see the level rise in the cup
Interacting with people was disturbing because she could not see them move
Vision was otherwise normal
brain processes the movement of a form separate from
the form itself
Visual agnosia
is the inability to recognize objects or pictures of objects—or the inability to draw a copy of the objects
Optic ataxia
a deficit in visually guided movements, such as reaching
Optic ataxia Associated with damage to
posterior parietal lobe
Prosopagnosia
the inability to recognize familiar faces
Alexia
difficulty reading
Apperceptive agnosia is an object agnosia in which the patient fails to
recognize a basic feature of the object, such as color or motion
In simultagnosia
the patient is able to perceive an object, but is unable to perceive more than one object at a time
Apperceptive agnosia , simultagnosia typically result from
bilateral damage to the lateral aspects of the occipital lobe
associative agnosia
patient can perceive the object, but they cannot recognize the object
Associative agnosia is typically associated with damage to the
ventral stream
Prosopagnosia patients Rely on recognizing a person based on the
sound of their voice, their hair, or the way they walk
Alexia is the inability to read Associated with damage to the
left fusiform gyrus and lingual area
Left hemisphere is specialized to combine
letters to form words
Alexia can be considered a
visual agnosia where the patient is unable to combine parts (letters) into a whole (words)
Visualization is important to
problem solving and other thought processes
Research suggests that imagery results from
top-down activation of visual areas, and may be initiated by prefrontal areas
Mental rotation of visual images uses
ight-hemisphere dorsal stream areas
