psychology of language - socsci.uci.edujsprouse/courses/w13/150/lectures/2.12... · psychology of...
TRANSCRIPT
Psychology of LanguageProf. Jon Sprouse
02.12.13:
UCICOGNITIVESCIENCES
synlab
PSYCH 150 / LIN 155
Lexical Access and the Temporal Lobe
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Stage 1: Activation of a competitor set
p kt f sθ ʃ htʃ m l
b gd v z ɮ ʔdɮ n rw
y aæ i e ɛ ɔʌ ə ou
ŋ
ð
ɪ
election
avow abuse eclipse eschew
electricity elect elector electorate
elated elapse ellipse elastic
ə l ɛ k ʃ ɪ nelection
As the physical stimuli unfolds, several potential words are activated based on their similarity to the phonetic signal.
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election
avow abuse eclipse eschew
electricity elect elector electorate
elated elapse ellipse elastic
Stage 2: Selection of the target word
p kt f sθ ʃ htʃ m l
b gd v z ɮ ʔdɮ n rw
y aæ i e ɛ ɔʌ ə ou
ŋ
ð
ɪ
ə l ɛ k ʃ ɪ nelection
The target word must then be selected from the candidate set (based on relative activation levels and other top-down information)
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Lexical access involves (at least) three neural components
p kt f
b gd
y aæ i
Phonological processing of the input (comprehension) or output (production)
So now the question is whether we can determine the cortical structures implicated in each of these components.
In this lecture we are going to use several language disorders to tease apart these components and their cortical substrates.
Stored meanings of the wordscaptain captive
Connections between the phonological processing component and the stored meanings
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Word Repetition
p kt f
b gd
y aæ i
captain captive
In word repetition, the participant is asked to repeat a word: “Say brick”.
Word repetition only requires phonological processing for success.
Neither the stored meanings, nor the connection to the stored meanings is required for this task.
It is easy to see that stored meanings are not necessary to succeed at word repetition:
Can you say this word blick?
Blick is not a word in English, so it has no meaning, and therefore your ability to repeat it must be independent of meaning.
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Auditory Comprehension
p kt f
b gd
y aæ i
Auditory comprehension tasks usually ask a participant to follow a command: “Move the green square”
Notice also that there is a directional component to the connections!
Auditory Comprehension taxes all three components of the lexical access system, but only in one direction: from phonological processing to stored meanings.
Success in these tasks requires phonological processing, connections to stored meanings, and stored meanings.
captain captive
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Naming
p kt f
b gd
y aæ i
Naming tasks ask a participant to name an object: “What is this?”
Notice also that there is a directional component to the connections!
Naming tasks tax all three components of the lexical access system, but only in one direction: from stored meanings to phonological processing.
Success in these tasks requires phonological processing, connections to stored meanings, and stored meanings.
captain captive
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Comparing tasks
NamingAuditory Comprehension
Word Repetition
Phonological processing
connections
meaning
By using all three tasks, we can assess which components of the system are intact, and which may be damaged.
Basically, if a participant succeeds on one but not another, we compare the requirements of each task to better identify which component may be damaged.
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Transcortical Sensory Aphasia
NamingWord Repetition
Patients suffering from TSA clearly succeed at word repetition tasks; in fact they tend to spontaneously repeat words spoken by others.
Many patients also succeed at naming tasks.
Auditory Comprehension
Patients suffering from TSA exhibit a catastrophic loss of auditory comprehension. It is basically obliterated.
This pattern of symptoms suggests that TSA is an impairment of the directional connection between meanings and phonological processing.
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Transcortical Sensory Aphasia
www.youtube.com/watch?v=bpeZ4xm62DM
Here is the only video of TSA that I could find on the internet:
This video demonstrates the repetition abilities of this patient; however, there is no evidence of spontaneous naming in this clip.
TSA is a very rare form of aphasia, and is usually associated with other impairments, making investigation of language ability difficult.
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Artificially inducing TSA
All of the electrodes implanted in the 6 patients.
Because TSA is very rare in stroke populations, Boatman et al. 2000 attempted to artificially induce TSA symptoms in surgery patients.
They implanted electrodes directly into the cortex of 6 patients (who were undergoing neurosurgery for epilepsy)
These electrodes delivered a small repetitive electrical current to the cortex areas between the electrode pairs.
They then tested the patients on a battery of language tasks while delivering currents to each location in an attempt to isolate the cortical locations that led to TSA-like symptoms (impaired comprehension, intact repetition and naming)
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Artificially inducing TSA
Electrode location for TSA like symptoms
Boatman et al. 2000 found that the following electrode locations lead to TSA-like symptoms: impaired comprehension with intact repetition and naming
These results accomplish two goals:
1. They establish the dissociation between the two directions of the connection between phonological processing and meaning.
2. They establish locations (for each individual) that may give rise to TSA-like symptoms.
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TSA vs M350
Locations that lead to TSA-like symptoms (Boatman et al. 2000)
Recall that the M350 indexes initial activation of lexical items: a mapping from phonological processing to meaning.
It is perhaps unsurprising that the location of M350 generators tend to overlap the location of TSA-inducing electrical interference:
Potential generators for the M350 (Pylkkanen et al. 2006)
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AnomiaAuditory Comprehension
Word Repetition
Patients suffering from Anomia succeed at word repetition tasks.
They also succeed at auditory comprehension.
Naming
Patients suffering from Anomia fail at naming certain objects.
This pattern of symptoms suggests that Anomia is an impairment of the directional connection between phonological processing and meanings.
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Anomia
www.youtube.com/watch?v=LWAUmsgk8eg
This is actually a pretty good example of anomic symptoms. Pay particular attention around 1:40 -- the doctor tries to give the patient a hint!
Anomia is more common than TSA, although I could only find one video of a patient suffering from anomia online:.
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Lesion sites for AnomiaAntonucci et al. 2004 investigated 8 cases of anomia (1 was an outlier, so there are 7 here). They found that the lesion site was always left temporal lobe, and that the more anterior the lesion, the worse the anomia.
anterior
posteriorLR
superior
Inferior
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Lesion sites for Anomia
In general, anomia results from diverse lesion sites across the left temporal lobe.
It is generally more inferior than superior, and more anterior lesions tend to be worse than posterior lesions.
Here I have overlaid the Anomia lesion tendencies with the induced TSA locations from Boatman et al. 2000.
This may make some sense: if we assume that meanings are distributed throughout the area, then the connections between meaning and phonological processing may also be distributed
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Category-specific AnomiaIt is relatively common for Anomia patients to demonstrate inferior performance on certain classes of nouns.
For example, Ferreira et al. 1998 report three patients who show more trouble with animals than tools.
Although rarer, there are also patients who show more trouble with tools than animal (e.g., Cappa et al. 1997).
This double dissociation suggests that living entities and inanimate objects may have distinct cortical substrates.
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Category-specific Anomia and Semantic networks
The existence of category-specific Anomia makes some sense given the semantic priming effects that we’ve already seen.
truck
fire engine
bus
vehicle
car
street
ambulance
redblue
house
fire
The spreading activation framework suggests connections between semantically related words.
Category-specific Anomia suggests geographic locality between semantically related words.
This suggests that spreading activation is indeed a physical/geographic process.
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No category-specific TSAGiven the existence of category-specific semantic organization, one might wonder whether there is category-specific phonological organization...
What this would mean in practice is that words that share phonemes would be organized together.
election
avow abuse eclipse
eschew
electricity
electorate elatedEvidence for this organization would be a category-specific version of TSA: difficulty comprehending words that share phonemes.
We have not encountered any patients with category-specific TSA, suggesting that words are not geographically organized by phoneme (but are organized by semantics). This makes some sense given the way we have conceptualized phonological processing.
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The picture so far
p kt f
b gd
y aæ i
lexical semantics
Anomia appears to be driven by a disruption in the connection between lexical semantics and phonological processing.
The model we’ve been using so far suggests two uni-directional connections between phonological processing and stored meanings (lexical semantics).
Transcortical Sensory Aphasia appears to be driven by a disruption in the connection between phonological processing and lexical semantics.
Is there a language disorder that appears to be a complete disruption of lexical semantics?
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Semantic DementiaWord RepetitionPatients suffering from Semantic Dementia are
successful at word repetition.
NamingAuditory Comprehension
However, they have problems both comprehending and naming certain words, but not others.
This pattern of symptoms suggests that the meanings of certain words are lost.
This suggests that phonological processing is spared in Semantic Dementia
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SD is a progressive deterioration of the temporal lobe
Semantic Dementia is a form of progressive fronto-temporal degeneration that targets the left anterior lobe more than the right anterior lobe, and tends to target the inferior portions more than the superior portions. It tends to begin in the temporal pole (blue area) and progress over time (yellow area)
SD is often contrasted with Alzheimer’s Disease, which is a progressive degenerative disease that tends to target parietal-temporal areas (blue areas), although it can also involve frontal areas as well.
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Video of Semantic Dementia
www.youtube.com/watch?v=fkKrsbwQvrE
Semantic Dementia is relatively rare, especially compared to Alzheimer’s. This is the only video I could find on the internet:
The early stages of SD are generally characterized by what appears to be word loss (similar to anomia), but upon closer inspection it turns out that the patients do not even know the concepts underlying the objects.
This patient appears to have progressed further toward some general symptoms of dementia.
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Semantic versus Episodic Memory
Semantic Dementia is characterized by a loss of semantic memory: knowledge of concepts themselves.
Alzheimer’s Disease is characterized by a loss of episodic memory: memory of events.
However, both are progressive diseases that lead to degeneration of much of the cortex and ultimately death.
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The picture so far
p kt f
b gd
y aæ i
lexical semantics
Anomia appears to be driven by a disruption in the connection between lexical semantics and phonological processing.
The model we’ve been using so far suggests two uni-directional connections between phonological processing and stored meanings (lexical semantics).
Transcortical Sensory Aphasia appears to be driven by a disruption in the connection between phonological processing and lexical semantics.
Semantic Dementia appears to be a loss of the concepts underlying the meanings of words.
Is there a disorder that targets phonological processing directly?
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Naming
Wernicke’s AphasiaAuditory Comprehension
Word Repetition
In patients suffering from Wernicke’s aphasia, all three tasks are impaired.
This pattern could suggest a catastrophic loss of language ability, but these patients do speak in what appear to be complete, grammatical sentences. But the sentences don’t make any sense, and may not even be composed of real words!
This suggests an impairment of phonological processing, which would then affect both comprehension and production of speech.
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Video of Wernicke’s Aphasia
www.medclip.com/index.php?page=videos§ion=view&vid_id=103628
Wernicke’s aphasia was first identified by Carl Wernicke in the late 1800s (~1874):
Wernicke’s aphasia is sometimes called fluent aphasia because they appear to produce fully grammatical sentences (albeit meaningless). It is also sometimes called receptive aphasia because of the difficulties in comprehension.
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Wernicke’s area
Wernicke’s aphasia tends to be caused by damage to an area of the superior temporal gyrus appropriately named Wernicke’s area, first identified by Carl Wernicke during postmortem examinations of patients demonstrating the symptoms of Wernicke’s aphasia.
Boatman et al. 2000 were also able to induce the symptoms of Wernicke’s aphasia with electrical interference at these electrode locations.
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Lexical access and language disorders
p kt f
b gd
y aæ i
lexical semantics
Semantic Dementia appears to be a loss of the concepts underlying the meanings of words.
Anomia appears to be driven by a disruption in the connection between lexical semantics and phonological processing.
The model we’ve been using so far suggests two uni-directional connections between phonological processing and stored meanings (lexical semantics).
Transcortical Sensory Aphasia appears to be driven by a disruption in the connection between phonological processing and lexical semantics.
Wernicke’s Aphasia appears to be driven by a disruption in phonological processing.
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