Auditory perception

Question 1

where is the primary auditory cortex/PAC/A1 located?

Answer 1

superior temporal gyrus, Heschl’s gyrus

Question 2

how is PAC organised?

Answer 2

tonotopically; tones close to each other in frequencies

Question 3

what is job of PAC?

Answer 3

1) segregate auditory objects

2) identify the location of sound in space

Question 4

what is in the cochlea?

Answer 4

receives auditory input
has different receptors that are selectively tuned to different frequencies
carries sound right up to PAC

Question 5

what is the PAC comprised ?

Answer 5

A1 is comprised of a core area

surrounded by the temporal lobe and angular gyrus

Question 6

what is the cortical arrangement of A1?

Answer 6

tonotopically arranged; striped arrangements of binarual inputs, containing EE and EI cells that help with the localisation of sound

Question 7

what are EE cells?

Answer 7

EE cells are contained within the stripes in A1

neurons in one stripe that are excited by both ears are EE cells

Question 8

what are EI cells?

Answer 8

EI cells are contained within the stripes in A1

neurons in the next stripe that are excited by one ear, and exhibited by the other ear are EI cells

Question 9

what do EE and EI cells do?

Answer 9

EE/EI cells alternating the auditory inputs are reminiscent of the ocular dominance in columns of V1 in visual system.

Question 10

characteristics of PAC/A1?

Answer 10

• activation of PAC in response to various sound freqs
• precise tonotopic map of cochlea
• information from ears is projected bilaterally to A1
• ipsilateral/input from the same side of ear to A1 is weaker than contralateral

Question 11

characteristics of A2/ secondary auditory cortex

Answer 11

-belt region surrounding A1 is A2..A2=parabelt regions
-A2 responds in a more diffused way to inputs in thalamus, less precise tonotopic organisation
…sorts out sound in a more meaningful way way, ie. perception.
-hierarchy when sounds are processed, A2 merges the complex sounds that A1 does not prefer. merges the frequencies together.

Question 12

Petkov and Kayser, 2006? monkey auditory cortex

Answer 12

map of PCA is more complicated

• 3 fields of PAC:
  1) prefers tones
  2) surrounded by 8 neighbouring belts of A2

Question 13

is fMRI a good measure of auditory activation?

Answer 13

fMRI is a poxy measure of neural processing in brain, its is not a direct measure
- fMRI measures blood flow to active regions of brain; we don’t have a high level of specificity in brain with fMRI

Question 14

Okada 2010? sentences and intelligibility

Answer 14

sentences render greater sensitivity in intelligibility of speech

• pSTS/ posterior superior temporal sulcus responds to the meaning of sounds (Wernicke’s area)
• if played a sentence backwards, activation of pSTS is significantly reduced
• pSTS only cares about the intelligibility of speech

Question 15

Rauschecker and Tias, 2000? functional task-specificity of A1

Answer 15

evidence that A1 is functionally separated according to task
the brain separates info and allows efficient sharing of task relevant information.
-study found that there are 2 processing systems in A1:
1) spatial stream, found in caudal part of superior temporal gyrus..projects to parietal cortex (similar to cortical visual pathway of object orientation i parietal cortex)
2) object/pattern stream, found in the anterior portions of the lateral belt/ anteriolateral area

Question 16

Alain, 2001? what and where of auditory brain

Answer 16

-pitch processing rendered greater activation of auditory cortex in the inferior frontal gyrus
-identifying location of sounds rendered greater activation of posterior parietal cortex
…there are specialised auditory streams, the ‘what’(pitch) and the ‘where’…exact same as vis system

Question 17

Clarke, 2002? patient studies

Answer 17

-JG had a lesion to temporal lobe, and had poor sound recognition
-ES had a lesion to parietal lobe, and had poor sound localisation
…functionally separate pathways that deal with diff types of tasks

Question 18

Formisano, 2008? speaker identity and component identification

Answer 18

• found separate regions of brain that respond to speaker identity and component identification
  …same as vis system, content of speech vs. who is speaking?

Question 19

study on damage to auditory system?

Answer 19

auditory aphasia= lesion to A1, renders cortically deaf

• bilaterally lesioned PAC-show no awareness of sound, but better than chance in identifying the orientation of sound…residual functioning of A1 despite damage
• lesion to one side of A1 renders in tact discrimination of sound frequencies, but poor localisation of sound on contralateral side

Question 20

what are Broca’s and Wernicke’s areas?

Answer 20

Broca’s area is about the physical speaking of language

• broca’s aphasia= speech is laboured and slow, non-fluent. affects written and oral speehc
• singing is more fluent in broca’s aphasia…singing might be separated from voice or speech processing

Wernicke’s area is about understanding language
- Wernicke’s aphasia= language understanding is impaired, spoken language is normal!

Question 21

Cathy Price, 2012? functional areas in language processing

Answer 21

Broca’s area associated with pOp
Wernicke’s areas associated with pSTS
…both involved in perception and production of familiar stimuli
wernicke’s areas in temporal hemisphere, lies within A2 and is critical to understanding language comprehension

Question 22

Hiokok and Poeppel, 2007? anatomy of language processing

Answer 22

-speech production found on dorsal paths, maps sensory representations onto motor representations
…action plans with speech, how can we articulate speech by using facial, mouth and oral movements of that sound

• speech perception found on ventral paths, maps sensory representations onto lexical conceptual meaning
• in speech production: Wernicke’s area (understanding speech) projects to Broca’s (speech production)

Question 23

Ghazanfar and Hauser, 2001? sound perc in other species

Answer 23

specialised processing of auditory syst in other species, species-specific vocalisations

Question 24

Lavan, 2017? laughing/ perc of other human vocalisations

Answer 24

laughs send out a social signal; can brain tell diff between polite (volitional)laughing and spontaneous laughing?..can we register authenticity of laughs?

• linear increases in responses in Heschl’s gyrus and superior temporal gyrus (STG) in authentic laughing
• linear relationship between arousal, valence and authenticity

Question 25

Sumby and Pollack, 1954?

Answer 25

what we see can affect what we hear

- speech comprehension improves when the talker is present

Question 26

Calvert, 1997? visual interaction with speech perc

Answer 26

silent lip reading activates A1 in MRI, even tho it is visual!
- speech related info from another modality can activate A1…stunning finding!

Question 27

McGurk effect, 1978?

Answer 27

vision can influence what we perceive
if auditory stim saying ‘ba’ and vis stim saying ‘ba’…ppl hear ‘ga’ or ‘da’
-sensory fusion