Transcript Temporal Aspects of Visual Extinction

Chapter 19: Higher mental functions
 Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders
University of South Carolina
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Methods of Study
 How do we infer brain function?
 Classically, we examined what went wrong when
someone had a disorder within the brain and inferred
that their injury was crucial for this task.
– Example: Patients with left frontal cortex injury have nonfluent speech.
 Now we visualize brain structures and localize
functional areas using advanced equipment and
technology
– Example: The left frontal cortex is activated during speech
production.
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Functional Localization (previous lectures)
Frontal Lobe
– Executive function
– Planning
– Sequencing
– Initiation – inhibition
– Voluntary movements
– Working memory
 Occipital Lobe
– Vision (Field cuts)
 Temporal Lobe
– Encoding long-term
memories
– Language
comprehension
– Hearing
 Parietal Lobe
– Reading/Writing
– Praxis
– Spatial processing
(neglect)
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Functional Localization
Functionalization occurs over period of time.
Brain becomes more specialized with
development
People who suffer brain injury early in life will
utilize existing brain regions in novel ways.
– Plasticity allows compensation
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Cerebral Dominance & Functional Specialization
Brain preprogrammed for different uses of right
and left hemispheres
Left Hemisphere
– Most people have left hemisphere dominant for
language
– Left hemisphere is called “Dominant” hemisphere
– Right handed people have longer planum
temporale in left hemisphere which may be biased
for use by dominant hemisphere
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Right hemisphere functions
 Right hemisphere involved in visual-spatial and
constructional tasks, emotion and emotional
intonation of speech and music.
 Right hemisphere is often referred to as the “Minor”
Hemisphere
 Patients with injury to right cortex often exhibit
neglect.
 Studies of lateralization can include tests such as
Wada test – Today most studies use fMRI for this
purpose
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Speech and Language Disorders
 Motor Speech Disorders
– Dysarthria - Paralysis or Paresis of Muscles
 Flaccid – LMN problem – hypernasal, breathy speech and
imprecisely articulated consonants
 Spastic – UMN – Harsh, strained / strangled speech with slow
articulation
 Hypokinetic – Basal ganglia – variable rate, excessive variation in
loudness and timing with distorted vowels
 Mixed – Combination of other dysarthrias
– Apraxia of speech - No Paresis, Programming Disorder
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Language Disorders
Aphasia
– Broca’s Aphasia - Broca’s Area
– Wernicke’s Aphasia - Wernicke’s Area
– Global Aphasia - Wide area
– Conduction Aphasia - Angular gyrus or inf. PL
– Anomic Aphasia - Angular Gyrus
– Transcortical Aphasia
– Subcortical Aphasia
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Language Production
Broca’s Area (1861)
Difficulty in speech production
Loss of ability to repeat speech
Comprehension intact
Foot of 3rd frontal convolution
(BA 44)
Left hemisphere (1865)
– Except left handers
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Language Comprehension
 Wernicke’s Area (1874)
 Normal production (speech sounds and
fluent nonsense)
 Sounds okay if you do not know the
patient’s language (e.g. Chinese
Wernicke’s aphasic would sound fine to
me)
 Unaware of deficit
 Impaired comprehension
 Left hemisphere
 Superior temporal gyrus
(BA 42, 22)
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Wernicke’s prediction
Predicted two language centers:
– Broca’s Area: speech articulation.
– Wernicke’s Area: language comprehension.
Predicted 3rd Syndrome:
– Disconnection syndrome
– ‘Conduction aphasia’
– Damage to
arcuate fasciculus
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Conduction aphasia
 Can comprehend speech
 Difficulty in repeating speech
 phonemic paraphasias (substitution errors)
 Lesions in Temporal Parietal Junction that knock out
underlying white matter
 Patients with damage ONLY to the arcuate fasciculus can
still generate speech.
– Why? Other pathways
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Wernicke-Lichtheim (1885) Schema
From auditory input (a) to motoric articulation
of speech (m)
Concepts
(Distributed)
Broca’s
Aphasia
Wernicke’s
Aphasia
Conduction
aphasia
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4: Transcortical Motor Aphasia
 Disconnection of Broca’s from
concepts
 Speech is slow, terse
 Can comprehend speech
 Found after damage to the
frontal lobes
 Unlike Broca’s Aphasics, can
repeat phrases when spoken
to
– direct Wernicke’s to Broca’s
pathway intact
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6: Transcortical Sensory Aphasia
 Disconnection of Wernicke’s
from concepts
 Can repeat words
 Speech is articulate nonsense
 Unable to comprehend speech
 Found after damage to the
posterior language area
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7 Pure Word Deafness
 Loss of ability to understand
spoken speech.
 Normal speech, reading, writing
 Behaviour and anatomy
dissociate from Wernicke’s
aphasia
 Written comprehension intact,
intact written/verbal production.
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Language Disorders
 Alexia
– with agraphia - supramarginal or angular gyrus
– without agraphia - medial occipital and temporal L.
– Aphasic alexia
 Deep dyslexia – large mixed lesions
 Surface dyslexia – Anterior left hemisphere
 Agraphia
– Pure agraphia - left superior frontal or parietal regions
– Phonological agraphia
– Lexical agraphia
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Alexia without agraphia
Disconnection of angular gyrus from visual
inputs
– Language outputs intact
– Patients cannot read
– Writing preserved
Rare: left and right pathways to angular
gyrus
Requires damage to
1. posterior callosum
2. left occipital lobe
Without damage to left angular gyrus
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Apraxias
 Apraxias (Other than Speech)
– Difficulty in carrying out learned voluntary motor acts
– Constructional: visual-spatial difficulty from RH
– Dressing: Spatial perception of clothing in relationship to
body
– Oculomotor: Difficulty in gaze
– Gait: Problems in walking
– Ideomotor: Trouble following commands
– Ideational: Trouble with multistep tasks – trouble with use of
objects – may confuse objects use
– Limb-Kinetic: Trouble with one limb only
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Aphasia Notes [lcbr.ss.uci.edu]
Type of
Aphasia
Broca's
Site of Brain
Damage
Broca's area
Comprehension
Speech
Repetition
Paraphasias
Good
Non-fluent, effortful,
usually agrammatic
Poor
Yes (phonemic,
semantic)
Wernicke's
Posterior STG
Poor
Fluent,
(para)grammatical,
sometimes jargon-like
Poor
Yes (phonemic,
semantic, neologistic)
Conduction
Supramarginal
Gyrus or auditory
cortex
Good
Fluent, grammatical,
self-corrective
Poor
Yes (phonemic)
Global
All of Perisylvian
Cortex
Frontal lobe
Poor
Very little
Poor
n/a
Good
Terse, echolalic
Good
Temporaloccipital-parietal
junction
Poor
Fluent, grammatical,
sometimes jargon-like
Good
Yes (phonemic,
semantic)
Yes (mostly semantic)
Varied, but inf.
temporal lobe
often involved
Lower motor
cortex
Usually auditory
cortex bilaterally
Good
Fluent, Grammatical
Good
No
Good
Dysarthric
Good
No
Very Poor
Fluent
Very Poor
In theory, no, but most
have paraphasias
Transcortical
Motor
Transcortical
Sensory
Anomic
Aphemia
Pure Word
Deafness
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Anatomy of aphasia
Transcorticalmotor
Broca’s
Wernicke’s
Conduction
Anomic
Global
Transcorticalsensory
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