Transcript Slide 1
Language
Ref: Banich Ch 9 pp. 286-293
Language: Brain Regions
Aphasia
Aphasia = language deficit resulting from brain damage
Two different “syndromes” result from damage to the
two key areas:
1. Broca’s aphasia - damage to Broca’s area
1. Wernicke’s aphasia - damage to Wernicke’s area
Broca's Aphasia: Typical Features
Production of speech:
• In short fragments, with many pauses
• Slowed, effortful
• Poorly articulated
• May be telegraphic:
Jim Hurdle: "Ah... Monday... ah Dad and Jim Hurdle... and
Dad... hospital. Two... ah... doctors... and ah... thirty minutes...
and yes... ah... hospital. And er Wednesday... nine o'clock. And er
Thursday, ten o'clock... doctors. Two doctors... and ah... teeth."
Broca's Aphasia: Typical Features
Comprehension of speech:
• Largely preserved
When the doctor discussed what a relief the weather was
compared with the cold, hard winter that they had been
experiencing, Jim pulled his sweater tightly around himself
and imitated a shiver.
Wernicke's Aphasia: Typical Features
Production of speech:
• Fluent, well articulated
• Function words present
• BUT often sounds “empty” of content
• Word substitution errors:
phonemic paraphasias
semantic paraphasias
neologisms
e.g. castle -> "cacksel"
e.g. camel -> "horse"
e.g. queen -> "robbli"
Wernicke's Aphasia: Typical Features
Examples:
You mean like this boy? I mean [noy], and this, uh [neoy]. This is a
[kaynit], [kahken]. I don't say it, I'm not getting anything from it.
I'm getting, I'm [dime] from it, but I'm getting from it. These were
[eksprehsez], [ahgrashenz] and with the type of [mahnic] is standing
like this... and then the...
"Yes... well of course when they came there, I ... em... he came there,
I didn't know... there and I didn't know anything for it, any... I
suppose we were there, when I went 1 2 3 4 5 and looked there and
said well so and so and so and so and so...”
Wernicke's Aphasia: Typical Features
Comprehension of speech:
• Impaired
• Can't follow conversations
• Can't obey simple commands
–
e.g. " Put the pencil on the card"
Classical Model of Language
• Broca's area = production ("articulatory images" of words)
• Wernicke's area = comprehension ("auditory images")
• Info is transmitted between the two:
Two Problems with Classical Model
•
Problem 1: Predicted Patterns Never "Absolute“
•
Broca's aphasics have some comprehension
problems:e.g. Reversible sentence comprehension:
“The boy is chasing the dog”
"I have to pay attention more carefully to what people are
saying now, because sometimes I miss things”
Two Problems with Classical Model
Wernicke's aphasics have production problems:
• Speech may sound “empty” of content
• Word substitution errors:
phonemic paraphasias
semantic paraphasias
neologisms
e.g. castle -> "cacksel"
e.g. camel -> "horse"
e.g. queen -> "robbli"
Two Problems with Classical Model
Problem 2: Symptoms of each syndrome dissociate
• Broca's aphasia:
articulation problems vs. sentence comprehension
impairment
• Wernicke's aphasia:
neologisms vs. semantic paraphasias
Current View of Language
•
Linguistics and Cognitive Psychology:
language seen as a complex hierarchical system.
•
Can describe language at a number of levels:
1. Phonological: what are the basic phonemes (sound
units) used to build words?
2. Syntactic: what are the rules for combining words
into sentences?
3. Semantic: what are the meanings of words, and how
does meaning change when words are combined in
sentences?
Current View of Language
• By this view, speech production and comprehension not
unitary processes, but involve multiple components.
For example:
• Production = syntactic planning, word selection, retrieval
of phonemes, articulatory programming
• Comprehension = auditory processing, access to word
meanings, syntactic processing.
Current View of Language
• Each of these components can become selectively
impaired in aphasia
• Some components located close together, so are more
likely to be simultaneously affected
• So, if you average across P’s, “syndromes” will emerge
• BUT minor damage can affect just one component
Current View of Language
• For many individuals, syndromes don’t work
• Therefore, some researchers now prefer the terms
Fluent and Nonfluent Aphasia:
Nonfluent aphasia:
• Anterior damage (usually)
• Covers Broca’s aphasia, as well as P’s with just one
or two features
Fluent aphasia:
• Posterior damage (usually)
• Covers Wernicke’s aphasia, as well as P’s with just
one or two features
Some Language Components
All of these can become selectively impaired:
Anterior (around Broca’s area):
• Articulation of speech
• Understanding syntactic relationships
Posterior (around Wernicke’s area):
• Retrieval of phonemes for production
• Selection of words for production
• Access to semantic info about words
Some Language Components
All of these can become selectively impaired:
Anterior (around Broca’s area):
• Articulation of speech
• Understanding syntactic relationships
Posterior (around Wernicke’s area):
• Retrieval of phonemes for production
• Selection of words for production
• Access to semantic info about words
i. Articulation of speech
Function of this Component:
• Generation of motor programs
or articulating words
Location:
• Overlaps with Broca’s area
Effects of Damage:
• Speech is halting, effortful
• Words may sound distorted
• P knows the sounds in words, but can't articulate
ii. Retrieval of phonemes
Function of this Component:
• Retrieval of stored info. about
the sounds that make up words
Location:
• Posterior: close to (partially
overlapping?) Wernicke’s area
Effects of Damage:
• P can articulate well
• BUT don't know which sounds to articulate
• Phonemic paraphasias in all speech situations…..
ii. Retrieval of phonemes (cont.)
Examples of phonemic paraphasias:
um.. tornet, no that's not right.. t.. turry-.. no.. turkey.. no... oh
gosh.. tur-.. turk-... turking..
that's wrong what's the end
part?.. um.. I can't remember...
other examples: castle -> cacksel
apron -> aben
refrigerator -> redjerfredjer
iii. Access to semantic info
Function of this Component:
• Accessing word meanings
• Involved in both production and comprehension
Location:
• Posterior -> temporal lobe, some
overlap with Wernicke’s area
Effects of Damage:
• P can’t define words
• Can’t match a word to its meaning
• Semantic paraphasias in speech...
iii. Access to semantic info (cont.)
a. Poor word definition:
bed: "Bed, bed, I don't
know what that is"
swan: "Swan, that
sounds familiar, I'm
sure I once knew it“
b. Failure at word-picture
matching:
Which is a picture of a newspaper?
iii. Access to semantic info (cont.)
c. Semantic paraphasias in speech and naming:
That’s some kind of animal, isn’t
it. A seal, is it?
other examples:
camel -> horse
son -> daughter
walking -> running
Anterior vs. posterior language areas
The general rule:
• Anterior = output
• Posterior = input
• This is broken here!
e.g. phoneme retrieval - posterior region, but affects output
more examples in later lectures…
• How do we explain this?
Anterior vs. posterior areas (cont.)
Posterior language regions (LH) are involved in:
Storage/retrieval of familiar, well-learned relationships
e.g. phoneme sequences of common words
meanings of common words
Anterior regions are involved in:
Generation of new combinations
e.g. sentences (novel combinations of words)
articulation (must be done afresh each time)
More about anterior/posterior differences in upcoming lectures…