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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.

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Presentation on theme: "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."— Presentation transcript:

0 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

1 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.

2 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

3 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

4 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

5 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

6 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

7 Ventral and Dorsal Streams
Parietal Lobe Frontal Lobe Dorsal Stream Visual Cortex Temporal Lobe Ventral Stream Dr. Lea Hyvarinen Helsinki, Finland, 2004

8 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

9 Ventral Stream What? yellow Recognition of . . .  faces
 facial expressions  colors & shapes yellow  letters and words  animals  objects Recognition of landmarks for stored routes so we can remember how to get home from work. 13

10 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.

11 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

12 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.

13 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

14 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

15 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

16 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

17 Dorsal Stream Where?  orientation in space
 eye-hand, eye-foot coordination  motion perception

18 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


20 27

21 28

22 Problems with Motion Perception
Uncomfortable around . . .  traffic  fast moving small animals  playgrounds

23 PEPI, The Dalmatian in Motion by Lea-Test Ltd. Copyright 2001

24 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

25 Multiple Visual Tasks 32

26 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.

27 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

28 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

29 Difficulty Scanning and Reading
Present small numbers of words at same time, enlarged, show them sequentially How are you? H o w a r e y o u ? H O W A R E Difficulty following movements Difficulty scanning the environment A lot of print on the page cannot be seen at once Moving head and eyes accurately to read is hard

30 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

31 Role of Other Lobes in Vision
Frontal lobe executes command functions to visually attend to objects and to turn eyes and head in anticipation 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 most important to focus on; everything catches their attention Motor Area Parietal Lobe Frontal Lobe Simply and structure the environment 38

32 Reticular Activating System
OT with SI training can provide ideas for ways to alert: Movement Massage Music Joint com-pression Arousal and Wakeful-ness Reticular activating system 39 Dr. Lea Hyvärinen, Helsinki, Finland, 2004

33 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

34 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

35 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. Damage to the Brain and Vision Impairment

36 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

37 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.

38 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

39 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


41 Traumatic Brain Injury
© 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

42 Infections Other Occur before or after birth Neonatal Hypoglycemia
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 peri- oxisomal -CVI in context of neurlogical deterioration along with many other problems

43 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

44 Optic nerve head in back child with 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 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 Child with Shunt Optic nerve head in back of the eye of 2 year old child with hydrocephalus

45 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

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