Lec 7 Hearing Brain 2 Flashcards
nature of sound
sound as outcome of physical movement, changes in air pressure
role of outer ear
amplifies frequencies, key in locating sounds
role of middle ear
converts airborne vibrations into liquid-borne vibrations
role of inner ear
converts liquid-borne sounds into neural impulses
what is tonotopic organisation
different regions in the brain area process different frequencies
Explain the ‘what’ pathway
Ventral route, found in temporal lobe, semantic content coded hear, also responsible for identifiyng ‘who’
Explain the ‘where’ pathway
Dorsal route, found in parietal lobe, codes where sound is coming from , also responsible for the ‘how’
define amplitude
loudness- high/low- the energy in a sound wave
define pitch
frequency in a sound wave
what is inter-aural differences
Difference in time taken for sound to reach one ear, dependent on position of sound source relative to head position.
Youmay hear a sound first/more intensely informing direction/location of sound source
head-related transfer function
Brain accounts for and corrects for the distortion of sound created due to head and outer ear (pinna) that are in the way of travelling sound
auditory stream segregation
complex auditory scenes (loud party/gig) can be divided into different processing streams for pitch, melody, location in space
Cocktail party problem (fMRI study)- method
p’s asked to attend to one of 3 people ina group i.e. low/middle pitched speakers
Cocktail party problem (fMRI study)- what 4 brain regions activated? what does each activatr?
IFG (inferior frontal gyrus) activation from pitch cues
Dorsal precentral sulcus (DPresCS) and superior parietal lobule (SPL) activation for location, IPS too
what can a spectogram show
physically depict speech as cmplex sound waves (darker areas are vowel- since they have a higher frequency
What features are used to produce the sound in our voices
Larynx and articulators
In a voice processing study, what happens in silent/passive conditions in the brain
Compared with silent c, bilateral activation in voice-selective regions of human auditory cortex
What does the adaptation paradigm show in a voice processing study
(listening to spoken syllables)
voice-selective area (right anterior superior temporal sulcus) sensitive to to change in speaker identity but NOT lexical-phonetic change
= voice processing NOT specific to humans- monkeys do it too
TMS effect on voice processing
TMS over the voice-selective area of brain disrupts the ability for voice detection. NOT for loudness judgement of same stimuli
What is the problem for Pure Word Deafness patients ?
Cause by what?
NOT actually dea, but cannot identify speech. Perceive speech as distorted, people sound too fast.
Causedby bilateral STG damage (Superior Temporal gyrus)
what is speech perception
set of operations transforming auditory signal into mental representations
Explain motor theory of speech perception
We perceive spoken words by reproducing a speaker’s movement in our vocal tract as opposed to identifying the sound patterns the speech generated by the speaker
What does the strong version of motor theory suggest?
the motor system for speech production is NECESSARY for speech perception
Name of key brain area associated with speech production
Broca’s area
Support for the Motor Theory
1) McGurk Effect (integration of visual info into what we hear)
2) Categorical speech perception- means we cant perceive sounds we cant produce
Neuroscientific evidence for motor theory
motor system is used in speech perception in a process of auditory-to-articulatory mapping
What is the opposing caveat to the supporting evidence for motor theory
If motor system is critical for perception of speech sound, then damage to motor speech production system should have substantial impact on ability to perceive speech.
(this is not always the case)
Evidence against the strong version of motor theory
From aphasic patients-
Hickok et al- Broca’s aphasia are non-fluent in speech production BUT when given speech perception tasks they perform well, suggesting motor speech system NOT necessary for speech perception
D’Ausilio et al’s virtual lesion study as more evidence against strong version of motor theory
The virtual lesions disrupted recognition of phonemes (labial/dental) after TMS applied but ONLY when presented in background noise
What does D’Ausilio’s virtual lesion study suggest about the PMC and speech perception
That the PMC (premotor cortex) only contributes to speech perception when the auditory signal is hard to disambiguate
Opposing evidence to McGurk effect
When TMS applied over superior temporal sulcus (STS) McGurk effect is disrupted
What has categorical speech perception study on phonemic discrimination taks suggested
Not just the motor cortex that processes speech categorically but whole network of brain areas
Conclude that there are multiple routes to speech perception, inc. WHAT (ventral) and HOW (dorsal) routes
Which of the two routes are more agreed on in research
the WHAT (ventral) path for semantics is more agreed on in research. The HOW (where, dorsal) route less agreed on- rather favoured by strong version of motor theory
