neurolin quiz 4

the dual stream hypothesis

ventral pathway - passes through the lower temporal lobes, important for understanding, connects phonological representations of sound to semantic meaning

dorsal pathway - connects the parieto-temporal cortex to the inferior frontal cortex. Important for production, is the sensorimotor interface between sound and articulatory motor centers

at 6 months - the quiet stage

peak synaptogenesis in the auditory cortex, more neural connections that are sensitive to different sound structures

at 9 months - the quiet stage

peak synaptogenesis in regions dedicated to language reception. The window for acquiring sounds natively closes, since we’re less sensitive to different sound structures

first words - 6 months

babbling begins, maturation of motor areas follows the maturation of sensory areas

first words - 10 to 12 months

infants say their first words.  The motor cortex and prefrontal regions connect with the temporal lobes.  This connection becomes stronger, allowing the dorsal stream to build on what the ventral stream learned.

• infants show an increase in inferior frontal gyrus activation as they listen to speech across stages of development

• the connections between auditory cortical areas responsive to hearing speech and those responsible for motor movements strengthens

• maturation of a mirror neuron system, hypothesized to play a key role in the binding of action, perception, and language, so infants can match what they hear to the motor action necessary for production

first words - 12 to 18 months

productions are very short, 50% are nouns. At 16 months only 25% of children combine words

first words - 18 to 24 months

telegraphic two word utterances become more frequent. By 24 months, 75% of children combine words, with 33% of them being nouns.

Language production is still very rudimentary, largely without morphology.  These children do not yet understand the basic syntactic categories of their language, “asyntactic integration”

between 14-20 months, there are clear differences in processing phonetically similar mispronunciations.  By 20 months, they require exact phonetic matches, while 14 month olds do not.  

ERP of known words vs unknown and backwards played words is lateralized to the left hemisphere by 20 months.

native language neural commitment hypothesis

the brain’s neural commitment to native language facilitates detection of native sounds and words. Strong native phonetic discrimination supports later language development

continued sensitivity to nonnative contrasts may reflect delayed specialization and does not typically facilitate native language learning.  Infants who are better at discriminating native sounds produce more words at 30 months

complex forms - 18 to 32 months

EEG studies show that children are able to process syntax around this age. Ungrammatical uses of both well known and newly learned words produced an early left anterior negativity followed by a P600-like late positivity

They aren’t just memorizing, they’re actively processing syntactic rules.

complex forms - 3 to 4 years

children can ask and answer questions, demonstrating their more advanced understanding of syntax.  The perisylvian regions continue to develop

complex forms - 5 years

children can talk about their experiences, desires, and goals in the past, present and future.  the language system is now essentially in place.  Further language development involves fine tuning.  Maturation of the prefrontal areas is important for cognition and integration of these areas with perisylvian regions to optimize connections for more complex language

two types of pure alexia patients

1. can recognize the letters of a word but cannot read it

2. cannot recognize the letters of a word

visual word form area

the brain’s ‘letterbox’

shows activation that depends on the degree to which a stimulus resembles a real word, it has a functional gradient in its selective activity for reading. Anterior part recruited for reading real words.  Located in the left fusiform gyrus at the temporo-occipital junction

regions and structures supporting literacy

• arcuate faciculus

• planum temporale

• other language areas including the temporal cortex and supramarginal gyrus

• visual cortex

early stage

• children learn a few whole words, usually proper nouns like their name

• the maturation of the dorsal visual pathway (visual occipital cortex, temporal, supramarginal gyrus) allows the development of invariant visuomotor representations. which is functionally coordinated during reading

• visual pathway converts letters to sounds

• the left occipito-temporal region that overlaps the visual word form area still functions off the assumption of mirror invariance, children think rotation does not change letter identity

• learning is transferred to the ventral pathway, so the child can learn the unique orientation of letters

• the left occipito-temporal region that overlaps the visual word form area now no longer assumes mirror invariance of letters, connection of written unit to meaning

phonological stage

children learn to map graphemes to phonemes:

• this stage is different lengths for different languages, depending on the opacity of the spelling system

• results from the maturation of the arcuate fasciculus, which connects the visual word form area to the superior temporal and inferior parietal regions, and the planum temporale

• white matter activation changes during reading and is correlated with reading skills

orthographic stage

• the phonology is well mapped and spelling conventions are adopted, reading becomes automatic and fast

• denser gray matter and increased connectivity between the visual word form area, the auditory areas and the planum temporale, including the arcuate fasciculus and the posterior corpus callosun

four groups of developmental disorders

1. neurogenetic disorders, caused by genetic abnormalities (down syndrome, williams syndrome)

2. behavioural disorders, defined on the basis of behavioural deficits, causes unknown (autism spectrum disorder and ADHD)

3. learning disability with an unknown cause - developmental disorders where the cause is not clearly genetic or environmental, they are language or reading specific (dyslexia, developmental language disorder, selective language impairment)

4. caused by environmental factors

down syndrome

trisomy 21

cognitive profile: significant intellectual disability

linguistic profile: expressive language is more delayed than receptive language.  relatively stronger social and pragmatic skills compared to syntax

williams syndrome

deletion of genes

cognitive profile: hypersociable or ‘over friendly’ personality.  Strength in facial recognition, weakness in numeracy and problem solving skills

linguistic profile: delayed but eventually relatively successful development.  problems in spatial prepositions, the pragmatics of conversation, and with more complex aspects of morphology

autism spectrum disorder

cognitive profile: impairments in social interaction and communication. Presence of restricted and repetitive interests or behaviours.  Strong genetic component, more common in males

linguistic profile: considerable variability in language skills, 15-50% fail to acquire functional language

early linguistic signs - delay, unusual intonation and usage, 25% experienced language loss, regression

phonology - prosody and intonation is unusual, in a mechanical or exaggerated manner, with inappropriate volume or speed.  Phonological differences impact prosody and social language

lexicon and syntax - inappropriate use of emotional and diectic terms, difficulty with argument structure and subject verb agreement

pragmatics

• echoed language with repetitive production

• idiosyncratic use of language, not abiding by conventional meanings.  problems with concept formation

• limited speech acts, difficulty with picking up the cues of others, moving from topic to topic and sharing interests

• rigidity in language use, verbal rituals demand a particular answer from a particular person in a particular manner, irritated and upset when interrupted 

ADHD

delayed or atypical brain development

cognitive profile: delays in executive functioning, impacting goal directed behaviour

linguistic profile: 

• speech may be rapid, impulsive, or poorly modulated with occasional disfluencies

• may produce more semantic errors and unrelated associations

• complex syntax can cause comprehension difficulty

• frequent interruptions, topic shifts, disorganized or tangential speech, difficulty understanding jokes, irony or indirect meanings, and poor self monitoring or conversational repair

two types of bilingualism

1. the ability to speak two languages

2. the simultaneous acquisition of two first languages

sensitive period

a period marked by increased sensitivity to certain inputs, such that learning shows a peak in efficiency and improved results

this coincides with specific neurophysiological events, like neuron formation, axonal projections, and synapses in particular brain regions.  After this peak, neuroplasticity is reduced and learning therefore becomes difficult.

Most restrictive for phonology, but none for the lexicon and semantics.

bilingual brain theories

1. the languages depend on the same brain regions

2. different languages depend on different regions of the brain

3. some regions are specifically dedicated to bilingual functions, such as language selection, switching, and translation

4. all languages depend on the same regions, but there are also neural networks that differ depending on the language

brain areas involved in bilingual functions

left inferior parietal lobule - allows us to monitor the linguistic environment

anterior cingulate cortex - engages the left prefrontal cortex, especially the dorsolateral prefrontal cortex

dorsolateral prefrontal cortex and premotor area - plays a key role in attention, decisions, and inhibition, and are therefore involved in language selection

caudate nucleus - overrides one language and allows one to switch to another language

basal ganglia - projects back to the cortical structures

low proficiency activation

increased in the right hemisphere. The later the age of acquisition, the more diffuse the activation, and the more it is varied among individuals

high proficiency activation

no difference in laterality between monolinguals and this group

white matter

have observed better connectivity and increased myelin in the white matter tracts of bilingual or multilingual people compared to monolinguals

this change can take place after very little exposure to a second language, but can also disappear quickly, highly dynamic

this bilingualism related neuroplasticity leads to increased connectivity of the white matter tracts between language areas

gray matter

age of acquisition and second language proficiency affect its density in the brain due to structural reorganization

learning an L2 can cause an increase in its density in the left inferior parietal lobule and other areas involved in language processing

its density is generally negatively correlated with the age of acquisition, and is greater as L2 proficiency increases.  But, the increased density is greater among school aged bilinguals than among late and early bilinguals 

neural reorganization triggered by bilingualism appears to follow an inverted u-shaped trajectory

1. initial exposure - increase in gray matter 

2. consolidation - increase in white matter connectivity, and therefore return to the gray matter norm

3. optimal optimization of networks, early and simultaneous bilinguals reach maximum efficiency quicker

inhibitory control

the ability to control and sustain one’s attention, behaviour, thoughts, and/or emotions to override a strong internal predisposition or external lure, and instead do what’s more appropriate or needed

working memory

the ability to hold information in mind and mentally work with that information to make connections or solve a problem

cognitive flexibility

the ability to change one’s own perspective or approach to a problem, to be flexible and adjust to the demands, rules, or priorities of a task or circumstance

bilingual advantage hypothesis

suggests that bilinguals benefit from increased domain general executive functioning

cognitive reserve effects of bilingualism

• can delay the onset of dementia by approximately 4.5 years

• these older adults recover quicker after a stroke

• functional degeneration and decline is slower

• may increase with each additional language, but eventually plateaus

• unclear if this is because it enhances tissue function or if the structural degeneration is just slower

attrition and the brain - pierce et al study

no behavioural differences between monolinguals, adoptees, and bilinguals at the n-back phonological working memory task, but behavioural data doesn’t give the whole picture:

• monolingual children showed more activation around the left lateral fissure in the insular cortex, which is a default language area.

• adopted and bilingual children show more activation in the right superior temporal gyrus region, which is linked to nonverbal memory, attention, and cognitive control

on top of traditional language areas, bilinguals and adoptees recruited additional areas related ton nonverbal memory, attention, and cognitive control.  The brains of adopted children more closely resembled L1 mandarin children than L1 french children, despite the fact that the adopted children no longer speak or understand mandarin

• bilinguals rely on general cognitive areas, while monolinguals rely on language specific areas

french monolinguals showed more left anterior insula activation, indicating more language specific processing of french sounds by those who were exposed to french from birth.

the adoptees and bilinguals showed weaker activation with similar patterns.

• they process the french sounds using a neural system originally tuned for another language

• the brain can adapt and use alternative neural systems where needed

• early language exposure shapes how this system develops and functions

even though an individual may appear to have completely lost their L1, ‘traces’ of that native language are still present at the neural level, strongly supporting the existence of neuroplasticity and biological sensitive periods

parallel recovery

the languages are recovered at the same time and rate, most common pattern, around 60% of cases but could be higher

selective recovery

recovery of only one of the languages of a previously bilingual person

Pitre’s law - the most dominant (frequent) language recovers

Ribot’s law - the oldest language recovers

differential recovery

languages recover at the same time, but at different rates, around 18% of cases

successive recovery

the recovery of one language after the other

which language is recovered first?

• the most familiar language (pitre)

• the language with the highest emotional association (minkowski)

• the most automated language, requiring the least effort

antagonistic recovery

a language is initially recovered, but as the other language recovers the first language is blocked.

It is possible for this recovery to alternate: the available language changes and they’re blocked alternately 

blending recovery

uncontrollable mixing of the grammar of multiple languages, even with the intention of only speaking one language. Disrupted ability to keep languages separate, about 9% of cases