Language part 2 Flashcards
Speech Production
Fundamentally a motor act dependent on
hierarchical planning
* Depends on pre-frontal areas
* Broca’s area
* In left hemisphere only (in most
individuals)
Broca’s Aphasia
language disorder caused by damage to Broca’s area, a brain region responsible for speech production.
Non-fluent speech
The patient struggles to form complete sentences.
Word-finding difficulty
Hesitations, pauses, and filler words (“ah,” “eh”) indicate difficulty retrieving words.
Agrammatism
Missing function words and grammatical structures (e.g., “Workin! Workin! Workin!”).
Comprehension mostly intact
Although speaking is impaired, understanding remains relatively strong.
Speech comprehension
Wernicke’s area helps with language comprehension and is in the left hemisphere (for most people). It relies on the ventral “what” stream for recognizing words.
Wernicke’s Aphasia (Fluent Aphasia)
Fluent but meaningless speech (“word salad”)
Normal grammar, articulation, and intonation
Uses incorrect or nonsense words
Severely impaired comprehension
Difficulty linking sounds to meaning (semantic issues)
Left hemisphere Specialization
→ Language
Broca’s area → Production & syntax
Wernicke’s area → Comprehension & semantics
Right hemisphere specialization
→ Spatial & emotional processing
Mental rotation, emotion perception, music
Detects prosody in speech
Split-brain studies → Severed corpus callosum → Hemispheres act independently
SPLIT-BRAIN
STUDIES
Can do two tasks at once (each hemisphere acts independently).
Right visual field → Left hemisphere → Can describe verbally.
Left visual field → Right hemisphere → Cannot describe, but can identify by touch.
Shows language is left-lateralized in most people.
Handedness
Right-handed: 80–90%
* Left-handed: ~10%
* Cross-dominant/Mixed-handed: ~10%
Language Lateralization
Right-handed: 95% left-hemisphere dominant, 5% right-hemisphere
dominant
* Left-handed: 70% left-hemisphere dominant, 15% right-hemisphere
dominant, 15% bilateral
RIGHT HEMISPHERE & LANGUAGE Prosody –
Intonation, tone, stress, and rhythm used for emotion, sentence form, irony, emphasis, contrast, and focus.
INTERACTIVE LANGUAGE NETWORK
Localization & distributed processing
Broca’s area – Syntax & speech planning
Wernicke’s area – Word perception & semantics
Sensory cortices – Auditory processing for speech
Motor cortices – Speech production
Association cortices – Semantic processing
Bottom-up & top-down influences
Recurrent & interactive processing
SOURCES OF INFORMATION
Genes – Learned over evolution
Past experience – Learned over a lifetime
Internal state – Learned in the current episode
Environmental context – Learned in the present moment
Proximal stimulus – The stimulus itself
Interactive Activation Theory (McClelland & Rumelhart)
A model of how different levels of processing (letters, words) interact in reading and perception.
McGurk Effect
A misinterpretation caused by conflicting auditory and visual speech cues.
Garden Path Sentences
– Sentences that trick us into misreading them because we interpret them word by word as we read.
Interactive Language Network
Broca’s area – Responsible for speech production and grammar.
Wernicke’s area – Involved in understanding words and meanings.
Sensory cortices – Process sounds, including speech.
Motor cortices – Control the muscles needed for speaking.
Association cortices – Help with understanding meaning and context.
fMRI: FUNCTIONAL MAGNETIC
RESONANCE IMAGING
Measures changes in magnetization, using electromagnetic
radiation and nuclear magnetic resonance.
FMRI path
Neural activity —) Increased blood flow —-) Change in magnetic field—)
fMRI BOLD signal
FMRI
Great spatial resolution (millimeters)
Moderate temporal resolution (seconds)
Non-invasive and low risk
Uses high magnetic field (1 to 5 Tesla)
Risks: Unsecured metal objects flying and shifting internal metal objects.
Meaning in the Brain
researchers are studying whether related words are processed in nearby brain regions and what that reveals about how meaning is structured in the brain.
Meaning in the brain step 1
Step 1: Find verbs
that co-occur with
nouns based on text
analysis
* Search online text
to find verbs near
each noun
Meaning in the brain step 2
Step 2: Identify brain areas whose
activation is associated with different verbs.
Meaning in the Brain step 3
Predict activation
for nouns as summation of
activation for related verbs.
