language Flashcards
language acquisition- phonology
- 3 months – eye contact with a speaking
adult and gurgling - 6 months - babbling
- 9 months- first ‘words’
- 18 months -speak 50 words and understand
150 words - 24 months – 500 words
dehaene-lambertz et al (2002)
fMRI of 3-month-old infant’s brain response to spoken words – results similar to adult
patterns of activation
activates planum temporale, superior temporal gyrus and temporal lobe
adult cortical language areas are already active in infants, before
the onset of speech production
phonological distinction and discrimination
- newborns are sensitive to almost every phonological
distinction yet tested - adults have difficulty discriminating speech sounds that are not contrastive in their native language
- this change happens at about 12 months
what are conditioned head turn tasks?
used to measure infants speech perception and phonological distinction
e.g r-l sounds detected by 10-12 month old american children but not japanese
what is responsible for the change in our
ability to discriminate ‘non- native’ contrasts?
- the maintenance/loss hypothesis
- functional reorganisation hypothesis
what is the maintenance/loss hypothesis of language?
role of experience is to maintain perceptual
sensitivities
lack of exposure leads to loss of perceptual ability
predictions from the maintenance/loss hypothesis
adults will be unable to perceive any contrasts that they have no had sufficient exposure to
children older than 12 months can move to a new country and require native phonology
what is the functional reorganisation hypothesis?
- no absolute hardware changes in auditory system
- development of a linguistic system that imports a subset
of the contrasts from the auditory system. - as babies acquire a linguistic system in their first
year, they “learn” which distinctions need to be
represented in that system
– enables categorisation
evidence of functional reorganisation and categorisation
during production of speech, children take statistics on the language they hear
distributions grow
babies absorb stats of lnaguage and this changes their brain to become culture-bound listeners
adults dont absorb the statistics
what is the mcgurk effect?
- shows that visual information is integrated into our perception of
speech automatically and unconsciously - the syllable that we perceive depends on the strength of the
auditory and visual information, and whether some compromise
can be achieved. - speech therefore makes use of all types of relevant information,
regardless of the modality. - there is some evidence that the brain treats visual speech
information as if it is auditory speech
e.g ditsnguish ba and fa only by looking at way mouth moves
what is aphasia?
partial/complete loss of language abilities following brain damage
what is the wada procedure?
used to determine hemisphere dominant for speech
inject sodium amytal in the left internal carotid artery
in most right and left handed people most has speech representation in the left hemisphere
left handed people did have more representation in the right hemi too
what is broca’s (expressive) aphasia?
- damage in motor association cortex of frontal lobe
- speech is nonfluent and agrammatical
symptoms of expressive aphasia
– difficulty speaking but can understand heard/read language
– pauses to search for words (anomia)
– repeats “overlearned” things,
– difficulty repeating words
what is wernicke’s (receptive/fluent) aphasia?
- damage in posterior temporal lobe
- fluent speech
symptoms of wernicke’s aphasia
- speech unintelligible
- poor comprehension
- appear undisturbed by their own speech
key anatomical elements of wernicke-geschwind model of language
- broca and wernicke’s aphasia
- acruate fasciculus
- angular gyrus
issues with the wernicke-geschwind model
i) words read do not have to be transformed into a
pseudo-auditory response
ii) severity of aphasia greater if cortical regions beyond broca’s and wernicke’s area are damaged
- does this suggest other regions are also involved?
what do parallel language pathways suggest?
language not based on a single stream of the acruate fasciculus
what are the parallel language pathways?
2 dorsal and a ventral pathway
dorsal parallel pathway 1
superior temporal gyrus with premotor cortex
speech production and
generating words
dorsal parallel pathway 2
superior temporal gyrus with
broca’s area
processing syntax- analysis of
words arranged according to
grammar
ventral parallel pathway
broca’s area to auditory cortex
– i.e. takes speech sounds and
extracts meaning
what is conduction/associative aphasia?
disconnection lesion of arcuate fasciculus and parietal
cortex
in contrast to broca’s aphasia and wernicke’s aphasia: comprehension good, speech fluent
symptoms of conduction aphasia
chief deficit: difficulty repeating words
- repetition substitutes/ words omission,
paraphasic errors, cannot repeat function or nonsense words, polysyllabic words
brain stimulation and language
study language function in living humans with electrical brain stimulation and
PET scans
3 main effects of brain stimulation on language:
1. vocalisations
2. speech arrest
3. speech difficulties similar to aphasia
what are the sites where stimulation affects language?
parietal and temporal cortex- produce vocalisations or impaire language (e.g generate aphasias)
brain imaging and language
largely confirms what we already know but there is more bilateral activation than expected
neurophysiology of language- timescales
language can be broken down into units at different timescales:
* short duration cues e.g. ba vs da -30-50Hz
* syllables – 4-7Hz (theta frequency)
* intonation– 1-2Hz
how does the brain transform continuous speech into a discrete code?
auditory info enters layer IV in the auditory cortex
this creates spike trains of neuronal firings
signals generated then become entrained (phase resetting)
firings of neurons become synchroned at different frequencies
e.g gamma (25-30) oscillations or theta (1-8)
this is outputted from auditory cortex to language processing regions by pathways from temporally organised spike train (output layers II/III)
intracellular speech disorders
speech development linked with a number of genes
1. mutation in FOXP2 (TF) - KE family (verbal impairment)
2. CNTNAP2- codes a neurexin protein and plays an important role in brain development
3. KIAA0319- neuronal migration and associated with dyslexia
how do we categorise speech sound disorders?
functional (no known cause) and organic (developmental/acquired)
