SLH 350 Test 2 PPT 1-3

Lecture 12

Neuroplasticity and Language Learning

Neuroplasticity

the brain’s ability to reorganize its structure and function in response to experiences

Two types of plasticity

synaptic/functional and structural

Synaptic/Functional Plasticity

Strengthening or weakening of existing synaptic connections

Changes in Synaptic/Functional Plasticity often rely on modifying the number of sensitivity of…

neurotransmitter receptors on the postsynaptic cell

Synaptic/Functional Plasticity happens when calcium entering the cell triggers…

chemical pathways that either build up or break down synaptic structures

In Synaptic/Functional Plasticity, these microscale cellular adaptations allow physical experiences to translate into…

lasting structural changes in the brain

Structural Plasticity

the brain’s ability to physically change its anatomical structure in response to learning, experiences, or injury

Structural plasticity happens when there is…

formation of new synapses, dendritic growth, and related physical changes

structural plasticity plays a role in…

childhood growth, lifelong adaptation, and injury recovery

Language as a lens for plasticy:

• rapid language acquisition in early life

• capacity for change in language acquisition persists across the lifespan

Eric Lenneberg

Renowned Linguist and neuroscientist who proposed Lenneberg’s original critical period hypothesis in 1967

Critical period is defined as:

a window from approx. 2 yrs to puberty when language acquisition happens

Critical period is attributed to…

declining cerebral plasticity with age

Lenneberg’s original critical period hypothesis key concepts

critical period, brain plasticity, and implication

critical period

limited time for natural language learning

brain plasticity

young brains adapt faster

implication of lenneberg’s hypothesis

children learn (especially languages) more easily than adults

Evidence for Lenneberg’s hypothesis

Genie - child victim of abuse who was not exposed to significant amount of speech from ages 20 months- 13 and was kept in a dark room and socially isolated

• she had no language when police found her at 13

• during a case study, she developed nonverbal communication skills but never fully acquired a first language

Ultimate attainment of a (first) language

achieving native-like proficiency in phonology (pronunciation) and intuitive grammar

Children are much more able to achieve ultimate attainment of a _________ ________ than adult learners

second language

Modern take is ________ not ________ period

sensitive not critical

Modern take: plasticity is elevated early in life but…

doesn’t shut off at a hard boundary

different aspects of language (phonology vs. vocabulary vs. syntax) may show…

different sensitivity windows rather than one uniform cutoff

In English, syllable level pitch pattern changes are not relevant to word meaning, but in Mandarin tones differ in their pitch pattern at the syllable level to…

distinguish word meaning

English listeners have trouble distinguishing the four tones in Mandarin, even if native english speakers are trained to learn Mandarin tones to near-native-like proficiency….

there are significant individual differences in our ability to learn them

adults show near native-like neural encoding of non-native speech sounds with training which shows…

neuroplasticity!

Subcortical processing of non-native speech sounds becomes…

more native-like with training (shows neuroplasticity in adults for L2 sounds is possible!)

This further discredits a ______ period and supports the _______ therory

critical, sensitive period

Understanding sensitive period windows informs clinical decisions like…

cochlear implants

Gene therapy research shows mutation in otoferlin (OTOF) gene causes…

childhood deafness, typically these children receive cochlear implants

Left hemisphere stroke in language areas can lead to

Aphasia

In some cases, the right hemisphere may reorganize to compensate for the loss of…

function in the left hemisphere after a stroke

right hemisphere gray matter structure predicts

language outcomes and relies on strong connections in the corpus callosum

plasticity is not just a….

developmental phenomenon, it operates across the lifespan

Lecture 13

Bilingualism

True or False: More than half of the world’s population speaks more than one language.

True

In the U.S. what percentage of residents speak more than one language?

21.9%

In the top five largest cities in the US (NYC, LA, Chicago, Houston, and Phoenix), what percentage speak a language other than English at home?

49%

simultaneous bilinguals

people who learn two languages from birth

successive bilinguals

individuals who learn their second language later than the first, such as through a language class or immersion (immigration to another country), etc.

L1

first language

L2

second language

Dominant/non-dominant language

how well the person knows the language

Age of Acquisition (AoA)

the age when someone starts learning a language, it separates simultaneous bilinguals from successive bilinguals

How do babies learn a second language?

bilingual infants must learn two linguistic codes

Bilingual infants learn two sets of…

phonemes, lexicons, grammatical systems, and eventually orthography

Most bilingual babies presumably hear the same…

total number of words as monolinguals

True or false: At birth, infants can distinguish between languages with different phonology (e.g. Tagalog and English), regardless of prenatal exposure to language.

True

Most phonemes are established at age…

6 months - 1 year

After 1 year, there is decreased sensitivity to

phonemes not in environment/native language

Are bilingual infants delayed in establishing the phoneme repertoire?

No!

Even though bilingual infants learn two sets of phonemes, it appears that learning of language phonology happens in…

parallel and at a similar timescale to monolinugal infants

phonotactics

what sound sequences exist in a given language

transitional probability

the likelihood that one sound will be followed by another, based on prior experience

By 9 months in monolingual infants, sensitive to the

phoneme sequences and transitional probabilities of their single native language

By 9 months, bilingual infants are also sensitive to sound-sequence patterns in L1 (comparable to monolinguals) but their discrimination is…

weaker in their L2, and the language that has less exposure will be learned more slowly

In a bilingual brain, is each language activated separately, or do the two languages interact with each other?

Interference!

Bilinguals likely activate both languages in…

parallel, then must express lexical selection for one

Semantic Interference

saying a semantically related word instead of the target one (ex. saying “apple” instead of “peach”)

For bilinguals, words in both languages belonging to the same category can cause semantic interference

not only saying “apple,” if you mean to say “cherry,” but also those words in the other language.

phonological interference

saying a phonologically related word instead of the target one (ex. saying reach instead of peach)

• can also occur across languages

Code switching

switching between two or more languages in one conversation

executive functions

a wide range of loosely defined processes related to activities such as attention, working memory, prospective memory, problem-solving, planning, cognitive flexibility, and inhibition

simultaneous activation

need for inhibitory control to speak in one language

cognitive control processes

adjust to specific demands of the environment

Two hypotheses explaining increased activation in bilinguals vs monolinguals during naming/reading

1. interference control hypothesis

2. reduced frequency hypothesis

interference control hypothesis

Knowing a concept’s name in 2+ languages means bilinguals must selectively activate the target language while suppressing competition from translation equivalents in the nontarget language

interference control hypothesis