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Vision and BrainScience B44

Lecture 23Brain

Damage

Brain Damage

1. Types of damage2. Agnosia3. Prospoagnosia4. Neglect

to eyes - injury, disease, cataractsto optic nerve - injury, diseaseto cortex - injury, disease, stroke, CO

1. Types of damage

Human cost, benefit to patientSpecificity of damage -- brain imagingLocalizing from loss of functionSerial hierarchy vs parallel pathways

What can we learn from pathology?

2. Visual Agnosia

damage to ventral pathwaycortical blindness or mind

blindnesscannot recognize objects, usually

cannot recognize faces eithere.g., patient DF cannot recognize

objects or even reportorientation

may include distortion of patterns, like DF’s caseor just inability to integrate, recognize or name

objects which are clearly seenin both cases, patient may make appropriate motor

responses to the object (dorsal pathway)occasionally, just recognition of faces affected

(prosopagnosia, Pauline)or spared (CK)typically permanent

2

Patient can see details but cannot name objectsor describe their function

But makes appropriate gestures with his hands

Objectrecognition

Lateral occipital cortexfMRI shows activity here when performing object

recognition tasksDamage here leads to object recognition problems:

visual agnosia

inability to integrate parts of objectin order to recognize or name itSometimes can use distinctive features to

recognize wholehigh contrast images often used as test for

loss of integration

visual agnosic often good at individual featuresbad at combinationsno worse than normals with mixed distractors

Easy for agnosicEasy for normal

Hard for agnosicEasy for normal

Hard for both

Visual Search

3. Prosopagnosia

Paulette

Can see details but can’t recognize familiar facesCan tell a face from a nonfaceEmotion recognition can be sparedRecognize friends from voice, gait, hair style, etc.

The Man Who Mistook His Wifefor a Hat

Intelligence, musical abilities unaffectedGradual onset from tumor (or degenerative disease

of visua areas)Problems with object and face recognitionRecognize friends from features, voice, gait, hair

style, etc.

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Congenital ProsopagnosicsDo not recognize friends, family, self. This bothersfriends a great deal.

Yesterday I went to pick my youngest son up fromdaycare. I did not recognize him, and I did not knowwho he was. I recognized him by his clothing.

I was about 12YO, and I was walking down an aisle thathad columns covered with mirrors (I have a LOT oftrouble with mirrors). I saw a girl walking toward me,and I thought to myself, "Boy, is SHE ugly!" You canimagine how depressed I was when I realized it was me!

Face recognition

Ventral temporal cortex:fusiform face area (FFA)

fMRI shows activity herewhen performing facerecognition tasks

Damage here leads to facerecognition problems -prosopagnosia

Why a face area?Need to recognize individual facesOnly need to identify the category of objectsThis is a beet or this a lobsterBut not an individual beet or a specific lobster agnosia without prosopagnosia

CK head injury at age 17 while joggingnormal visual acuity, language, reasoningdraws well but can’t identify latercan’t identify food in cafeterialarge toy soldier collection as a child

Can lose object recognition butspare face recognition

Normals

CK

66%

68%

inverted

71%

14%

disguised

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Video of CK

Prosopagnosia(Paulette)

earlyvision

objects

faces

words

Double dissociation

patient CK

objects

faces

words

earlyvision

loss of attention or awareness to contralesional sidedamage to dorsal pathway (parietal lobes)difficulty in moving attention around in that fieldespecially if competing item in good field bisection task, clock task

4. Neglect: deficits for left side of worldleft side of objects (at any location)left side of visual fieldleft side of imageryleft side of dinner

typically temporarysometimes deny any

lossimplication for logic

of thought?

Artist’s selfportraits as herecovers from

neglectArtist sees these asnormal and complete

drawings

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Imagery and neglectloss of attention or awareness to

both sidesdamage to both parietal lobesreport only one object at a timeeyes never movetypically temporary

Balint's Syndrome

Balint's Syndrome

Types of damageAgnosiaProspoagnosiaNeglect

1 Minute QuizMonday - finals for

Observation paper prizes

Summary

Agnosia: loss of object recognitionProsopagnosia: loss of face recognitionCongenital prosopagnosia: lost since birthDouble dissociation: two deficits that are lost

independentlyNeglect: inability to move attention to one side of

spaceBalint’s syndrome: inability to move attention to

either side

Glossary