Lecture 15: Bilingualism Flashcards
Damage to Broca’s Area does not
ALWAYS result in Broca’s aphasia
Dronkers et al. (1996) reported 22 patients with
damage to Broca’s area identified by imaging –
but only 10 had Broca’s aphasia. Damage to
underlying white matter, subcortical structures
High-resolution MRI revealed that lesions in both cases
extended into more medial brain regions than Broca
could have observed
Broca’s aphasia: Comprehension
problems
-agrammatism: deficits in processing
grammatical aspects of lanaguage.
-“The boy ate the cookie” understood (little demand for access to grammatical rules; never
think “the cookie ate the boy”)
-“The boy was hit by the girl” might be
misunderstood (grammatical rules needed to
disambiguate who hit whom)
Not just production problems, also comprehension.
agrammatism
deficits in processing
grammatical aspects of lanaguage
Broca’s area shows increased activity
during processing of grammatically
complex sentences
The child enjoyed the juice that stained the rug”
(simple)
“The juice that the child enjoyed stained the rug
(complex)
Broca’s area shows increased activity
during processing of grammatically
complex sentences
Association of Broca’s area solely with
motor word images in classical model is too
simplistic
Wernicke’s Area
Carl Wernicke
reported on
patients who:
-had fluent speech
-but nonsensical sounds
-or nonsense sentences
Wernicke’s area
near auditory cortex
-Wernicke thought that this area is involved with
auditory
storage of words, which he believed would result in problems with word comprehension and producing meaningful
sentences (can’t choose right words, can’t monitor verbal output)
Wernicke’s Aphasia: Fluent Aphasia
Not a Perfect Association between
Wernicke’s Aphasia and Damage to
Wernicke’s Area
In one study involving 70 patients with Wernicke’s aphasia, 7 had brain damage
confined to regions outside Wernicke’s area
Other studies indicate that Wernicke’s aphasia occurs only following damage to
Wernicke’s area and surrounding posterior temporal lobe regions, or damage to
white matter paths that connect these regions to other parts of the brain
Wernicke’s Aphasics have Output
Problems as well as Comprehension
Problems
Sometimes have naming problems
Classical View of wernicke’s aphasia and how it has changed
Wernicke’s aphasia reflects loss of linguistic
knowledge, which impairs comprehension
- Evidence against the classical view: Wernicke’s aphasics show intact
semantic priming on a lexical decision task despite problems with
explicitly comprehending the semantic relationship between words,
e.g., “doctor” primes lexical decision to “nurse” even though
patients fail to comprehend relationship between the two when
explicit judgment is required. - Perhaps reflects a problem with processes that normally provide
access to linguistic information for explicit, goal-directed use in real-
time. - Evidence favors the idea that patients cannot integrate words into
the context of a sentence quickly enough to allow normal
comprehension
Are Broca’s and Wernicke’s areas
involved only in heard/spoken languages,
or do they serve a more general
linguistic function
Evidence from American Sign Language (ASL)
3 groups were scanned with fMRI while processing
sentences either in written English or ASL:
1) Normally hearing, monolingual,native speakers of English
who did not know any ASL.
2) Congenitally deaf individuals whose native language was
ASL and learned English late/imperfectly
3) Normally hearing “native signers” who were born to
deaf parents and learned both ASL and English
as their native language
Cortical areas displaying activation for English sentences (vs.
nonwords) for each subject group.
Neville et al.
Broca’s and
Wernicke’s
areas active for
hearing group and to
some extent native
signers, but not
for deaf
Broca’s and
Wernicke’s
areas active
for deaf and
native signers, but
not for hearing
Broca’s and Wernicke’s areas
We can think of Broca’s and Wernicke’s areas as two nodes in a larger left
hemisphere language processing network that is critical for both comprehension
and production. Damage to the entire network produces global aphasia – problems
with both comprehension and production.
global aphasia
Damage to the entire language processing network network produces global aphasia – problems
with both comprehension and production.
There are Costs Associated with Bilingualism
- Generally reduced vocabulary in each language compared with
monolinguals - Slower to name pictures and commit more errors than
monolinguals - More prone to tip-of-the-tongue states
Early negative views of bilingualism
(1) Children who are instructed bilingually from an early
age will suffer cognitive or intellectual retardation in comparison with their monolingually instructed
counterparts.
(2) They will not achieve the same level of content master
as their monolingually instructed counterparts.
(3) They will not achieve acceptable native language or
target language skills.
(4) The majority will become “anomic” individuals without
affiliation to either ethnolinguistic group
The early negative views have been challenged and largely
replaced by a much more positive picture emerging from research in
cognitive psychology and cognitive neuroscience
Cognitive Neuroscience of Bilingualism
Two general issues
- Nature of bilingual brain function: What brain mechanisms
control language use? - Effects of bilingualism on the brain What effect does
bilingualism have on brain function and cognition?
Language Use in Bilinguals
- Both languages of bilinguals are active when using one of them:
semantic priming of lexical decision occurs equally when prime and target are in same language (e.g., body-hand <ready-hand) and when they are in different languages (e.g., cuerpo-hand<listo-hand). - Transfer of semantic priming across languages implies common
underlying conceptual/semantic representation. - Neuroimaging studies indicate that overlapping regions, including Broca’s and Wernicke’s area, are recruited by L1 and L2 (esp. in early bilinguals; e.g., Kim et al. 1997, Nature).
How does bilingual brain distinguish and control
which language is in use?
Since both languages are activated during language use, and
overlapping regions are recruited by L1 and L2, a fundamental problem for the bilingual brain is to distinguish and control which language is in
use.
Crinion et al. (2006, Science) developed a novel approach, using a semantic priming paradigm.
Logic: identify brain regions whose response to semantic priming (i.e.,
reduced activity or adaptation) is language dependent. Such regions
should be able to distinguish which language is in use.
Key finding: In bilinguals, the left caudate uniquely showed a language-
dependent semantic priming effect
Semantic priming task: Subjects instructed to make a
yes/no semantic decision about the second word in
response to a question about its meaning
1) Prime and target in same language with unrelated meanings (e.g.
ladle–SHOWER; bathtub–SPOON)
2) Prime and target in same language with semantically related
meanings (e.g. bathtub– SHOWER; ladle–SPOON)
3) Prime and target in different languages with unrelated meanings
(e.g. suppenkelle– SHOWER; badewanne–SPOON)
4) Prime and target in different languages with semantically related
meanings (e.g. badewanne–SHOWER; suppenkelle–SPOON)
Used both German-English and Japanese-English bilinguals.
Behavioral semantic priming occurred regardless of whether prime and
target are in the same language or different languages
Left caudate involvement in bilingual language
processing: Neuropsychological evidence
Abutalebi et al. (2000, Neurocase) studied a trilingual (Armenian-English-
Italian) woman who suffered a stroke in the left caudate.
Preserved comprehension in all three languages; picture naming above 80% accuracy in all languages.
Main problem was loss of control over which language she
was using: during language production, she spontaneously and involuntarily
switched among her three languages.
Supports the idea that left caudate plays a role in controlling/selecting
specific language.
Caudate is part of basal ganglia; plays a role in controlling and selecting
motor sequences.
What brain mechanisms
control language use
Neuroimaging evidence indicates that left caudate as well as other prefrontal
cognitive control regions are important for controlling which language is in use
Stroop Effect
Slower to Name Color When Color and Word Don’t
Match (Incongruent) than when Color and Word Match (Congruent)
Stroop Effect
Incongruent – Congruent
Smaller Stroop effect for bilinguals
Bilinguals also show enhanced performance compared with monolinguals on several other
tasks that require executive/cognitive control – effects observed for children as well as young
& old adults.
Bilingualism: * Both languages of bilinguals are active when using one of them
- Evidence from semantic priming
Reaction times for making a decision about a word speeds up when 2
words are in the same language (e.g., body-hand) AND when they are in
different languages (e.g., cuerpo-hand)
* This transfer of semantic priming across languages implies that you
access a common underlying conceptual/semantic representation
of words in BOTH languages
- However, there is no perceptual priming across languages
Studying “horse” primes the exact word “horse” on a word-stem
completion task, but doesn’t prime “caballo”
* Thus, there is a separation between conceptual knowledge of a word
and its physical form
Selection processes (i.e., selecting what is relevant, ignoring the rest)
Given that both languages are active, there is constant, inherent competition between
the 2 languages
* Bilinguals require a mechanism that allows them to constantly select the appropriate
language and practice effect on selection
Bilinguals are more accurate at detecting abnormal grammatical violations, a task that
requires them to ignore the misleading meaning of the sentence abnormality and focus
only on the grammar
* Example: “Apples grow on nose.”
Bilingualism and Stroop Effect
- Stroop effect: People are generally slower to name a color when the
color and word don’t match (incongruent) than when the color and
word do match (congruent) - Requires overriding what the word says to name the color (taps into executive
control)
Bialystok & Craik (2010): Bilinguals show reduced stroop effect
(i.e., are not slowed down as much) compared to monolinguals
- Bilingualism can also confer advantages in the context of Alzheimer’s and
dementia
- Bilingualism can also confer advantages in the context of Alzheimer’s and
dementia - Mechelli et al., 2004: Bilinguals show increased grey matter density in left parietal
region (active during word fluency/generation tasks), and activity in this region is
positively correlated with proficiency- protective factor in brain tissue atrophy?
Bialystok et al, 2007: Bilinguals have a later onset of Alzheimer’s despite less
education than monolinguals à may constitute a source of “cognitive reserve”
(i.e., higher education levels and engagement in other simulating activities) that can
protect against onset of dementia-related decline
Impact of Bilingualism on the Brain
Grundy et al., 2017: Neuroimaging of bilingualism
* When first learning a new language, bilinguals rely on prefrontal resources to help
resolve competition between languages (i.e., deciding which language to choose)
- Over time, there are increases in grey matter in multiple brain regions, as well
increases in white matter that connect anterior regions (involved in cognitive
control) and subcortical/posterior regions (for motor and perceptual processing) - Eventually, bilinguals rely less on anterior regions and more on
subcortical/posterior regions – “BAPSS” (Bilingual Anterior Posterior Subcortical
Shift) à shift from top-down processing requiring cognitive control, to more
automatic processing
Semantic priming:
Faster to make a judgment about a word if the
preceding word is semantically/conceptually related
Brain regions sensitive to semantic priming of a words should show
reduced activation when words are semantically related
Brain regions sensitive to semantic priming that is
LANGUAGE DEPENDENT should be able to distinguish which language
is in use (i.e., reduced activity for words in the same language but
not if words are in different languages)
