Lecture 6: Language

Language

distinctive to humans, flexible/evolving (slang), human communication/cooperation, mysterious

Language Definition

arbitrary system of communication, meaning is AS w/ symbols, mvmts, sounds

Language does

1) not require reading/writing → writing is recent, requires instruction, talking without reading/writing
2) not often use proper grammar → don’t always speak according to the rules for comprehension to be possible
3) may be separate from thought and cognition → thought preceded language → 1) think w/o language 2) think about language → different networks for cognition and language → ex. Infants → understand before speaking

Phonemes

smallest units of sound

vary by language, languages have diff sound libraries and distinctions

• English (r/l) - Not in Japanese, Arabic (c/k) - Not in English, brain ties to native language by 1 year

Phonemes - Accent

sound distinctions in one language that aren't recognizable or differentiated in another

Morphemes

smallest units of meaning, ex. S (plural), un (changes meaning)

Making Words

parietal, frontal areas involved → vocal response, motor programs (speech/sound prod.)

Syntax

grammatical rules by which we construct sentences, varies by language

• can recognize correct syntax even when a sentence is meaningless, ex. Colourless green ideas sleep furiously

• correct syntax does not guarantee clear meaning, ex. we loving hurting people

Syntax - Ambiguity

ex. “Call me a cab” → very context-dependent and clear with context/experience

Contextual Information

important for understanding language, resolving ambiguity with context

Language Acquisition

learned by immersion into the language, slight innate ability to learn and use it

• observational learning, experimentation, reinforcement, and shaping + innate ability to learn and use it

• when language is absent in a population, they may develop one → Nicaraguan Sign Language + Creoles

• ex. Creoles → forced labourers created language, ex. Nicaraguan Sign Language → isolated children

Language Acquisition - Development/Motivators

• with age, sensitivity to non-native phonemes is lost, speech is slower in boys/bilingual homes
  1) motivation for communication, 2) context varies (immersion), 3) neuroplasticity declines, 4) mechanisms of learning language change with age, 5) less likely to achieve native proficiency

Distribution Representation

any lobes can be involved in language, depending on task (speech prod, read, write) but language is thought to be partially separate from, but in connection with other cognitive networks

Language Lateralization

spoken + signed language are lateralized to left hemisphere, Wada Test or fMRI

Wada Test

invasive, use drugs to deactivate one hemisphere → task → measure performance

Implications of Lateralization

can still process information but cannot produce language

• damage to left (stroke) → language impaired, cut corpus callosum → right hemisphere, appropriate actions

• ex. Right stimuli → left hemi → verbal response, left stimuli → right hemi → no verbal, but can draw

Prosody

meaning of language can be affected by pattern of rhythm, pitch, stress, intonation

Linguistic

ex. “Lets eat grandma”, left hemisphere, IFG and STG

Affective

“i am fine” vs. “i am fine!” → emotion and right hemisphere

Aprosodia

seen in disorders, tendency to take things literally, right hemisphere injury

Music

speech is different than sound, speech → left lateral, inferior temporal, sound → right

Wernicke-Geschwind Model

brain areas though to be involved in two separate processes, older model
1) comprehension of written words → O (read) → T (comprehend) → P (articulation)
2) responses to heard question → T (auditory, hear) → T (comprehend) → P (articulation)

New Model for Language

1) Dorsal Pathway 1 → speech preparation, premotor cortex,
2) Dorsal Pathway 2 → syntax, pars opercularis, superior temporal gyrus
3) Ventral Pathway → word comprehension, STC (superior temporal cortex)

Visual Word Form Area (VMFA)

reading, left fusiform gyrus, recognizing words, objects, patterns

Neural Recycling

VMFA, brain area for a new purpose, originally visual pathway (object), now word

Lesion Studies

ventral temporal cortex lesions → category-specific semantic deficits

• Suggestion → concept attached to these things are now mapped onto different parts of the brain

Dissociation Studies

some patients unable to name living, while others unable to name nonliving

Category-Specific Brain Activation

differences within and between categories (living, right) (tools, left)

• ex. Cat morphs into dog → as the image changes, the portion of the brain that's responding, changes too

Bilinguals

different words are represented in different areas, but are similar across languages (-invariant)

Within a Category

specificity increases from domain-level at posterior (O/T) to specific-level at ant (MT)

• patients with aphasia get the domain right but the specific name wrong

Concept Distinction Theories

1) Visual vs. Function Distinctions → living things defined by appearance, tools by utility
2) degree/kind of visual distinctions → living things have many visual features (complexity)

Brain Decoding

concepts → certain BAs in a predictive way → study brain → dictionary → BA → words

ERP

event-related potential, measured using EEG, neural activity related to brief mental process

Letter/Number

N/P → direction of potential (negative or positive), number → time after event

N400

process words in a sentence in context, words early may prime words expected later → when expectations are wrong (prediction error) → neural signal, the more unexpected = stronger signal (scaling)

• not the result of surprise (ex. CAPITALS) but the result of surprising meaning (unusual word)

• comprehension ability → amplitude is lower with injury, less surprised when we can’t understand

P600

syntactic violations (grammar errors), inferior frontal cortex active during complex syntactic processing

• with experience, people exhibit a neural response to abnormal sentences in that language

N170

expertise with visual stimuli and reading proficiency, left-lateralized signal in reading experts (automatic), signal early in training is predictive of future reading proficiency

Aphasia

difficult in producing or understanding language, common after stroke

Dysarthria

difficulty in movement of muscles in producing language

Apraxia

difficulty in replicating actions

Dyslexia/Alexia/Hyperlexia

abnormal reading, inability to read, fixation but not comprehension

Strokes

interruptions in blood flow, in middle cerebral artery (MCA) of the brain

Word Comprehension

overlap with stroke lesion, include areas involved in comprehension, deficits common

Broca’s Aphasia

difficulty in producing language (non-fluent), comprehension less affected, aware of deficit

• Broca’s Area (left inferior frontal, BA44), involved in motor for production, also impairs sign language

Treating Broca’s Aphasia

melodic intonation therapy (MIT), right hemisphere through music, re-routes

Wernicke’s Aphasia

receptive aphasia (meaningless sentences), unaware of deficit, left hemisphere damage → deficits in comprehension of sign language

Things to Remember

1) brain injuries affect many areas 2) brain areas have more than one function

Animal Vocalizations

specific sounds made in specific circumstances with clear meaning → ex. Rats laugh when tickled, male mice sing to find mates → most are food-associated vocalizations

Language vs. Vocalizations

• species has limited number, tend to be for specific situations + specific meaning → not really emotional

• human language is flexible, communicates infinite amount of ideas and interpretation is based on context

• animals can learn human language but with low proficiency, do not generate own words or use w/e/o

Language Evolution

• cortex development, white matter tracts (frontal), genetic mutations (FOXP2), vocal track

• roots in gestural communications → ex. Mirror system for grasping, bipedal (free hands), tools → speaking

White Matter Tracts

humans have interconnected inferior F/P and lateral/inferior temporal, apes lack it

FOXP2

transcription factor, in basal ganglia, mutations in humans with impairments

• adaptive variant accelraise language development, positive selection, transgenic mice = better performance