Visual Processing in
the Brain and Damage
to the Visual Brain
Developed by the
SKI-HI Institute
Utah State University
Spring 2011
For use in VIISA
Training
The Visual Brain
•
The brain devotes more territory to vision
than all other senses combined (40%)
•
There are 32 distinct areas in each
hemisphere of the brain involved in
visual processing.
1
Information Leaving the Retina
• Retina: changes light energy to neural
signals and performs computations on
those signals, processing
• Axons leaving the eye are
heterogeneous, carrying different
types of information:
spatial and depth
motion
color
lines and form
• Some go to subcortical areas of the
brain, leaving the main optic path
before the LGN
• Most continue to the LGN and on to
the Visual Cortex
2
Key Subcortical Functions: SCN
• Controls sleep-wake cycle
• Production and release
of some hormones
• Changing time zones,
neurons in SCN need
time to retrain to new
light-dark cycle
• Implications for sleep problems in children who are
blind
3
The Accessory Optic System (AOS)
• 3 separate nuclei in the
brainstem
• Project to the cerebellum and
spinal cord
• Play critical role along with
vestibular and proprioceptive
systems in:
-visual stabilization
-postural control
-regulating locomotion
and heading
4
Other Pathway Destinations
• Superior Colliculus:
Initiation and control of
orienting movements of
eyes, head and body to
things in the peripheral
fields and fixation on them
• Some control pupil size
• Some in brainstem to
control eye muscles
• Some in spinal column to
control muscles in neck,
trunk and limbs
• Improved head and trunk control also often leads to
improved visual functioning
5
Lateral Geniculate Nucleus and V1
• Projects to the cerebral
cortex
• Almost all the fibers
terminate in the primary
visual cortex or V1 area
• All subcortical areas not
only receive information
from the eye but also the
V1 area
• They are also connected
with each other as well as
hearing and touch
6
Ventral and Dorsal Streams
Parietal Lobe
Frontal Lobe
Dorsal
Stream
Visual Cortex
Temporal
Lobe
Dr. Lea Hyvarinen
Helsinki, Finland, 2004
Ventral
Stream
7
Why do we need these two visual
systems?
Visual Perception
• Helps us make sense out of the outside world
• Allows us to create representations of it that can be filed
away for future reference
Guiding Action
• Requires accurate information about actual size, location
and motion
• Has to be coded in the absolute metrics of the real world
• Has to available in real time
8
Ventral Stream
What?
Recognition of . . .
 faces
 facial expressions
 colors & shapes
 letters and words
 animals
 objects
Recognition of landmarks for stored
routes so we can remember how to
get home from work.
13
Studying Brain Injury in the Old and the
Young
• We are learning a lot about how the visual brain works
from adults who have suffered brain injuries from
strokes, trauma, oxygen deprivation, etc.
• They are able to talk about what and how they see in a
way that young children with brain injury can’t.
• Brain injury to young children may affect the visual brain
in similar ways.
• But in the very young child, brain plasticity may help the
visual brain rewire to some degree around the lesions.
• Depending on where, when or how much damage
occurred, visual functioning may vary.
• This is an exciting, emerging field of study.
10
Dee
• Case discussed in “Sight Unseen” by
Goodale and Milner
•
Suffered carbon monoxide poisoning
•
A few days after the injury, she could
walk, talk, hear, but not see.
•
Over time, regained conscious sight,
but sight without form. She could not
see edges or outlines of objects
•
Objects had to have a distinctive color,
smell or texture for her to recognize
them.
•
When she touched the object, she
could then recognize it.
11
Dee’s Dorsal Stream Functioning
• She could reach out and grasp a
pencil accurately and use it.
• She could use her hands well for
many daily tasks.
• She could get around her
environment well.
• She could hike over difficult terrain
Vision for perception was profoundly
affected and vision for action
unscathed.
lh3.ggpht.com
12
Dee’s Ventral Stream Function
(15 years later)
• Could not recognize short printed words on a page
• Could not recognize faces or drawings and photos of
every day objects
• Trouble separating object from background: knife and fork
next to each other were too similar and looked like a blob
• Difficulty naming geometric shapes, even when on
contrasting background; but when felt, she could name
them
• Could not copy simple pictures, but could draw from
memory
• Damage to her ventral stream had a profound impact on
her visual functioning
13
Damage Can Be Specific to a
Function
For example:
 Can not recognize a familiar face. . .
but can see it, reach for it, and
touch the face
 Can match faces. . . but not be able
to name who they are
 Acuity can even be normal
Dr. Lea Hyvärinen,
Helsinki, Finland, 2004
18
Facial Recognition
Ways children compensate for loss of face
recognition:
 May recognize people by their voice.
 May always ask who they are.
 If have problems with auditory
recognition, may use other cues
instead, for example:
 color of shoes
 smell.
Let the child use whatever compensatory technique works for
them.
Sometimes, may need to teach slower child how to compensate.
20
Getting Lost in His Neighborhood
• Little boy would get lost in his own
neighborhood
• Could not find best friend’s house
even after repeated walks to it
• Was not able to recognize, use,
remember landmarks to help him find
his way to and from
• A ventral stream function
• He had good acuity
• Looking at alternative supports such
as written directions for him to follow
to get to places
www.pbase.com
16
Dorsal Stream
Where?
 orientation in space
 eye-hand, eye-foot coordination
 motion perception
17
Problems with Motion Perception
• Rare and called akinetopsia
• See stationary objects quite well
• When object moves relatively quickly, they lose it
Woman who:
• Difficulty pouring coffee into cup because she could not
see liquid rising
• Saw movement as a series of snapshots
• Daily scenes looked like jerky, strobe-like movements
18
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27
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Problems with Motion
Perception
Uncomfortable around . . .
 traffic
 fast moving small animals
 playgrounds
22
PEPI, The Dalmatian in Motion by Lea-Test Ltd. Copyright 2001
30
Perception of Objects in
Space
If damaged, these children may . . .
 get lost easily
 have difficulty with accurate reach
 have difficulty with eye-hand/
eye-foot coordination (stepping
on/off curbs, across sidewalk
cracks, or changes in floor
surfaces)
 difficulty in crowded situations
Dr. Lea Hyvärinen,
Helsinki, Finland, 2004
31
Multiple Visual Tasks
32
Infants/Toddlers: One Thing at a Time
• Visually being aware of multiple things takes time to
develop and mature
• Infants and toddlers focus on one thing at a time, and
may ignore the rest of the world
• For some children, this skills may be delayed, so they
may trip over, bump into things, fall off a curb when
focused on something they see at a distance, ignoring
the obstacles along the way
• In the absence of an ocular disorder or CVI, this
corrected itself over time, and the children were able to
handle multiple pieces of information.
26
Damage to the Parietal Lobe
 Visual array may need to be simplified
 Child may
need to use
a cane
 Child may need to move closer to
block out background in order to
simplify the visual array and focus
on the single most important item
34
Damage to the Parietal Lobe
 Visual array may need to be simplified
 Child may
need to use
a cane
 Child may need to move closer to
block out background in order to
simplify the visual array and focus
on the single most important item
35
Difficulty Scanning and Reading
Difficulty following
movements
Difficulty scanning
the environment
Present small
numbers of words
at same time,
enlarged, show
them sequentially
How are you?
A lot of print on
the page cannot
be seen at once
Moving head and
eyes accurately to
read is hard
How are you?
H
O
W
A
R
E
29
Specific Problems
Lesions to parietal lobe can result
From brain bleeds, strokes, etc.
Specific visual problems:
• Loss of ability to direct the arm
toward a visual target that they
can look at
• Reach to a target, but cannot
direct gaze to it
• Can see and reach to a target
but not adjust grasp to it
images.teamsugar.com
30
Role of Other Lobes in Vision
• Frontal lobe executes command
functions to visually attend to
objects and to turn eyes and
head in anticipation
Motor Area
Parietal Lobe
Frontal Lobe
• Parietal lobe works closely with
frontal lobe and motor cortex to
do this
• Damage to frontal lobe can make
it hard for child to decide what is
• Simply and structure
most important to focus on;
the environment
everything catches their attention
38
Reticular Activating System
Arousal
and
Wakefulness
Reticular
activating
system
Dr. Lea Hyvärinen,
Helsinki, Finland, 2004
OT with SI
training can
provide
ideas
for ways to
alert:
Movement
Massage
Music
Joint compression
39
Organizing the Child for Using
Vision
Reduce amount of incoming stimuli
for child who is easily overwhelmed.
Help organize the visual system
with massage, joint compressions,
gentle movement, soothing
sounds.
40
Ways Visual Information is Handled in
the Brain
• The reflexive or primitive visual system
• The higher visual system
--Where
--What
•Both of these high level visual systems can be damaged
to varying degrees with a wide array of affects seen.
• Each child shows a unique combination of features
• When primary visual cortex and processing centers are
damaged, vision problems occur (CVI)
43
•
Damage to the
Brain and •
Vision
Impairment •
Focal damage to the visual brain leads to
specific visual difficulties
Diffuse damage affects all aspects of brain
function, including visual processing
Simple problems affecting visual acuity, field
and contrast are easy to identify
•
Abnormal development of or injury to the optic
radiations, visual cortex and visual processing
areas (ventral/dorsal streams) result in vision
problems
•
The role of perceptual and cognitive visual
dysfunction in many other disabilities such as
intellectual, autism, cerebral palsy, may not be
recognized or understood.
35
Acquired Neurological Injury:
Hypoxic-Ischemic
•
•
•
•
•
•
•
•
Brain needs glucose and oxygen.
When deprived of one of these, potential
for long term brain dysfunction exists.
Asphyxia is lack of oxygen. Too little
oxygen (hypoxia) disrupts regulation of
blood supply to the brain, creating too
little blood flow (ischemia).
Severity and duration of episode
determines extent of damage
Organ damage, CP, seizures, hearing loss, CVI
When causes irritation to brain-encephalopathy
Numerous causes (e.g., PP, twin-to-twin, maternal diabetes or infection)
Can occur in utero, during birth, after birth; mostly in preterm newborns
36
Periventricular Leucomalacia
• Most common neurological lesion in the
preterm infant (24-34 weeks)
• White matter damage in the watershed zones
of the immature brain
• Due to hypoxic-ischemic event-brief or
profound impairment of blood flow to the area
so no oxygen; preterm or perinatal-different
effects
• Affects superior part of optic radiations
(result is lower field loss); subcortical
white matter that serves vision and association
areas (processing); oculomotor nerve damage
• Wide range of visual and cognitive functioning
• Field losses, visual/spatial problems, crowding
interpreting complex visual patterns.
37
Focal Brain Lesions
• Includes such things as: arterial or venous stroke, intracranial
hemorrhage, focal tumor
• Nature and range of visual impairment depends on the location
and extent of the lesions
• At first, visual attending is poor, but usually acuity ends up OK,
but there is field loss
• Unilateral lesion behind optic chiasm may lead to homonymous
field defect
• Acuity is impaired when lesion is extensive or bilateral
• Eyes move to target in blind hemifield, overshoot, then correct
with microsaccades
• Need to learn to scan
• Central loss due to stroke, turn eyes away from field loss
• Severe stroke can also lead to CP, seizures, delays
38
Intraventricular Hemorrhage (IVH)
•
•
•
•
•
•
•
•
•
Low birthweight premature babies may suffer
brain bleeds in and around the ventricles
Germinal matrix is just outside the ventricles;
incubator for brain cell production
In preterm, this area abundant in fragile blood
vessels
Events causing too little or too much blood
flow to area can lead to a bleed
Bleeds graded from I to IV (worst)
Optic radiations pass by and around the
lateral ventricles
These bleeds can damage the optic
radiations, resulting in vision loss
Severity of vision loss depends on the extent
of the bleed, treatment, other medical issues,
etc.
Grade III-IV bleeds can lead to CVI,
CP, hydrocephalus, delays
Lateral Ventricle
Optic
Radiations
Lateral Ventricle
(other views)
Grade III Bleed
in the Lateral
Ventricles
39
40
Traumatic Brain Injury
© VictorPowell.com
• Shaken baby or accidents
• Lead to: hemorrhaging, diffuse damage to axons, increased
pressure in brain then hypoxic-ischemic events
• Damage can be focal, multifocal or diffuse
• The brain injury can result in CVI
• At first, visual recovery may be rapid, but not complete
• Optic nerve atrophy seen later, poor visual prognosis
41
Infections
• Occur before or after birth
• TORCH infections passed
from mother to fetus (CMV,
Herpes, rubella, toxo)
• Result can be CP, seizures,
CVI
• Some ocular conditions such
as cataracts can occur with
these
• CMV and meningitis can lead
to vision and hearing loss
• Vision loss can be CVI, optic
nerve atrophy or nystagmus
Other
• Neonatal Hypoglycemia
-if not treated, brain injury can
occur; results in poor cognition,
motor problems, epilepsy
• High Bilirubin
-Chronically high; leads to hearing
loss, abnormal swallow and
speech, visual gaze problems
• Metabolic Disorders
-mitochondrial, lysosomal and perioxisomal
-CVI in context of neurlogical
deterioration along with many
42
other problems
Brain Malformations
• Alterations in normal progression of
brain development has neurological
consequences
• Include things like:
-Spina Bifida, Dandy Walker Syndrome
-microcephaly, lissencephaly,
schissencephaly, hydrocephalus
-agenesis of corpus calosum
• Result from chromosomal disorder,
infections, or idiopathic
• Mild to severe developmental outcome
• Present early with poor visual attention
• May also see optic nerve anomalies,
CVI, nystagmus, seizures
Lissencephaly
43
Hydrocephalus
•
Increased fluid in the ventricles or water
spaces of the brain
•
Put pressure on optic nerve fibers; vision
transient or episodic due to vascular
dysfunction or hypertension in brain
Child with Shunt
•
Prolonged high pressure causes
permanent damage
•
Putting in shunt to drain fluid soon enough
can minimize the damage
•
Decreased visual functioning can be a
sign of shunt failure
•
Acuity problems, strabismus, field loss, visual
perceptual problems
www.mps1disease.com
Optic nerve head in back
of the eye of 2 year old
child with hydrocephalus
www.nature.com/
44
Chromosomal Disorders
• Trisomy 13 and 18
• Common eye problems:
-microphthalmia
-coloboma
-abnormal optic nerve and eye
structures
-CVI
Epilepsy
• Uncontrolled seizures, lead
to poor acuity and attention
• Exclude diagnosis of infantile
spasms with infants who have
unexplained vision loss
45