PSY 401 Exam #2 Flashcards
what are the 2 main computational channels for speech processing (DM)?
dorsal stream: auditory motor functions
ventral stream: comprehension
what is spectrotemporal analysis? where is it conducted in the brain?
- SA: computation of which sound frequencies are present in the environ and their moderations over time; input received via signals from the thalamus
- conducted in Heschel’s gyrus [A1] + dorsal plane of superior temporal gyrus [STG]
DUAL STREAM MODEL BEGINS HERE
what are the 3 proposed steps of hierarchically organized speech perception?
- dorsal STG carries out early spectrotemporal analyses
- mid-posterior lateral STG represents subphonemic features and feature combos
- mid-posterior STS represents individual phonemes and sequential phonol. structures of whole words
where are sub-phonemic features of speech processed?
L mid-lateral STG; HALFWAY POINT of the stream
what is categorical speech perception? where in the brain has it been represented?
- different versions of the same general phoneme are perceived as being the same, even when they vary acoustically
- there is NOT a 1:1 mapping of acoustic signal and phoneme id
- mid-lateral STG
where in the brain are phonemes/phonological structures of words stored?
L mid-posterior STS
what is phonological neighborhood density? where in the brain are they activated?
- the # of words that differ from a target word by only 1 phoneme ex. BET - bit, bat, get, pet (dense)
CHURCH - ? (sparse)
- the # of words that differ from a target word by only 1 phoneme ex. BET - bit, bat, get, pet (dense)
- DENSELY POP WORDS TAKE LONGER TO PROCESS
- word neighborhood activation occurs in the MID-POST STS (step 3)
hierarchical pathway of speech perception: top down v bottom up processing
BOTH occur:
- bottom up: acoustic information from environ
- top down: expectations from experience! hypothesis, trying to prevent prediction errors
entrainment
process by which the frequencies of connected speech correlate with rhythms of neural activity / brain wave oscillations
- is this an aquired assoc? the brain waves match to any speech rhythm being perceived? - No sabemos
- INCREASED syncing assoc w INCREASED perception
do fMRI/PET experiments imply causal relationships?
- NO; just bc an area is active during a task DOESN’T mean it’s necessary for that task –> must look at neuropsych/brain damage data
is speech perception a uniquely L Hemisphere process?
- NO; studies show that R hemi is also active in speech percep processes
- patients w L hemi superior temporal brain damage acutely only have moderate SP issues –> R hemi can get the job done
Wada procedure + implications
- sedative administered that “immobilizes” 1 hemisphere in order to test LATERALIZATION of diff behaviors/brain functions
- i.e. if L hemi is inactive, will this behavior be impaired?
- -> most times NO
- i.e. if L hemi is inactive, will this behavior be impaired?
- further implies bilateral nature of early cortical speech perception
word deafness + implications
- neurolog. disorder where speech percep is disrupted but hearing is intact; caused by BILATERAL lesions to Mid-Pos STG (both hemis must b damaged)
[SPARES HESCHEL’s GYRUS/A1]
- further implies bilateral nature of early cortical speech perception
asymmetric sampling (AST) in time method
the left hemisphere may be dominant for detecting and categorizing rapidly changing signals (e.g., cues for place of articulation), whereas the right hemisphere may be dominant for dealing with longer signals (e.g., cues for manner of articulation)
- R HEMI: slow fts (manner)
- L HEMI: fast fts (place)
initial evidence for dual streams in speech percep: comprehension + repetition
- conduction aphasia [IMPAIRED REP, INTACT COMP] v transcortical sensory aphasia [IMPAIRED COMP, INTACT REP]
- suggests SEPARATE processing stream or comprehension + articulation/repetition
what are the 2 functional components of the ventral stream (DM)?
- lexical interface
2. combinatorial network
ventral stream: lexical interface - what does it do?
- a relay station for linking phonological structures of words —> their semantic structures/meanings during spoken language comprehension
- does NOT store meanings!! just is a middleman for connecting to them
where is semantic knowledge stored in the brain?
- all over! distributed across the cortex
what is a lemma?
- an abstract word node; intermediary stage between semantic meaning and phonolo. structure of a word, while maintaining syntactic info [ex. whether concept it’s a noun or verb]
ventral stream: combinatorial network - what does it do?
- links together the integrated meanings of words and sentences; word and sentence level compreh.
- sensitive to syntactic and semantic fts of speech [i.e. responds during passive listening to SENTENCES but not to just a list of nouns]
dorsal stream: sensorimotor interface - what does it do?
- maps phonological structures of words to vocal tract movement / speech motor areas of frontal lobe
- p21
dorsal stream: articulatory network- where is it located?
- located in PM, pIFG, ant insula
dorsal stream: sensorimotor interface - where is it located?
- located in area SPT in the planum temporale
- covers 4+ distinct cytoarchitectonic areas
dorsal stream: articulatory network - what does it do?
- needed for speech production
ventral stream: lexical interface - where is it located? what does damage here lead to?
- L Posterior Middle Temporal Gyrus (pMTG) and p Inferior Temporal Gyrus (pITG)
- stimulation here induced Trans Sens Aphasia [IMPAIRED COMP, INTACT REP]