Neurobiology of Language Flashcards
cognitive neuroimaging methods
MEG and fMRI
what is magnetoencephalography?
MEG records magnetic fields generated by brain activity to indicate levels of electrical activity
how are magnetic fields measured?
using highly sensitive magnetism detectors SQUIDS which are arranged in a helmet to detect localised brain activity
benefits of MEG
easy to use
good spatial
excellent temporal resolution
non-invasive
used alongside MRI scans to show physical structure also
what does functional MRI detect?
changes in the oxygen activity of the blood in the brain, by using magnets to measure brain signals from protons in the body
rhythm
pattern of events that have a repeated, predictive structure
what is the basal ganglia (BG) involved in?
the perception and structure of rhythm, as it is connected to:
- outer layers processing sound (auditory cortex)
- areas controlling movement (premotor cortex, cerebellum)
what does the Putamen do?
this activates when predicting how the beat of music continues
neural resonance theory
electrical signals of the auditory and motor system automatically create coordinated oscillations
- the brain synchronises electrical activity to the beat
oscillations
the synchronised activity of millions of brain cells
frequency bands of different neural oscillations
- delta (less than 3Hz)
- theta (4-7Hz)
- alpha (9-13Hz)
- beta (14-30Hz)
- gamma (above 30Hz)
what does speech consist of?
the actual use of spoken language as oral communication
what does talking require use of?
tongue muscles and vocal tract in a precise and coordinated way
the dual-stream model of the functional anatomy of language:
lexical interface and higher semantic processing is bilateral
spectro-temporal and phonological network is bilateral
articulatory network and sensorimotor interface is left-dominant
where is phoneme processing represented?
in the bilateral phonological network
where are phonetic features encoded?
in the superior temporal gyrus, and each brain area has specificity to each phoneme sign
high neighbourhood density words
phonetically similar to many other words, with 11 or more neighbours, e.g., one sound substitution/deletion/addition
hierarchal rhythmic structure of speech:
prosody intonation-
temporal integration window of >500ms and frequency <2Hz
syllables-
temporal integration window of 200ms and frequency 5Hz
phonemes-
temporal integration window of 25ms and frequency 40Hz
what does speech comprehension involve?
- sentence context
- prosody intonation
- syllable word
- phoneme transitions
syllable
unit of pronunciation having one vowel sound, with or without surrounding consonants, forming the whole or part of a word
- speech intelligibility is dependent on syllable rate
auditory speech
speech envelope
visual speech
lip movements
what is speech-tracking (entrainment)?
the synchronisation between speakers’ oscillations and the listener’s brain oscillations
what is auditory speech entrainment modulated by?
intelligibility
- low-frequency (delta, theta) speech tracking is right-lateralised
- high-frequency (gamma) speech tracking is left-lateralised
what is speech-tracking served by?
top-down modulation transfers to the auditory cortex
evidence of visual speech being important for successful comprehension
cocktail party problem
what do individuals with stronger speech-tracking in the left motor cortex have?
better comprehension
prediction of speech syllables facilitates communication:
- predictive comprehension
- production planning
- speech
communication and joint action- what are sent and received?
both speech signals and non-speech signals
face-saving indirectness
involves using a public face for respect and trust
brain areas activated for the indirectness effect:
- medial prefrontal cortex
- bilateral temporoparietal junction (TPJ)
- bilateral inferior frontal gyrus
- bilateral middle temporal gyrus
what does understanding face-saving language require?
cognitive perspective taking and other discourse-relevant cognitive processing
mutual understanding
when different minds mutually infer they agree on an understanding
what is the production and comprehension of novel communicative behaviours supported by?
right lateralised fronto-temporal network
what is the right lateralised fronto-temporal network necessary for?
embedding utterances in conversational context, through pragmatics and mental state inferences
why is white matter important for information processing?
higher cognitive functions, e.g., speech, are distributed in areas with connections through WM bundles
different language networks:
dorsal pathway
ventral pathway
dorsal pathway
crucial for processing complex sentences, connected to:
- broca’s area
- precentral gyrus
- premotor cortex
ventral pathway
connects ventral portion of the inferior frontal gyrus to temporal cortex, via the extreme fibre capsule system
myth of language lateralisation
only needing the left hemisphere for language is a myth
which language processes are left-lateralised?
syntactic comprehension and production
which language processes involve both hemsipheres?
sentence-level semantics engage the left and right posterior temporal gyrus for comprehension and production
when does language processing become more bilateral?
with age, to compensate for structural changes, even in left-lateralised processes
what does communication in a social context rely on?
right-hemisphere contribution, such as:
- affective language processing
- understanding nuances such as face-saving indirectness
what does the act of communication as a joint action engage?
a right-lateralised fronto-temporal network
