Audition Flashcards
Amplitude
Intensity of sound (LOUD)
Frequency
Number of compressions per second (hz) pitch is related to freuqncey
Sound travels in ear
Sound wave-> eardrum-> ossicles(hammer,anvil, stirrup)-> oval window
Corti composed of …
Basilar membrane
Tectorial membrane
Basilar membrane
Auditory receptors, hair cells are mounted here.
Tectorial membrane
Rests on hair cells
Mechanism of sound detection
- Tympanic membrane activates ossicles
- stirrup makes oval window vibrate setting in motion all the fluid in the cochlea
- Basilar membrane containing organ of corti pulsates moving hair cells
- Hair cell is sheared by tectorial membrane
- Opening ion channels in membrane of neuron and signal travels down axon
Frequency mechanism 1
Low frequencies up to 100 hz
Basilar membrane vibrates in synchrony with the sound wave producing 1 action potential per wave
Number of neurons activated determines intensity
Frequency mechanism 2 (volley method)
> 100 hz
A neuron phase locked to the parks of sound waves
Each sound wave produces a volley of impulses he various fibers
Up to 5000
Place mechanism
> 5000 hz
Cochlea base basilar membrane is narrow and stiff
Cochlea apex basilar membrane is wider and not as stiff
Vibration strikes basilar membrane and sets up a traveling wave
Max displacement at particular place along the basilar
Traveling wave for low frequency vibration peaks at or near apex
Higher frequencies, point max displacement is closer to base
Axons of each auditory nerve synapse in the…
Ipsilateral cochlear nuclei
From ipsilateral cochlear nuclei…
Many projects lead to superior olives on both sides of brain stem
From superior olives…
Axons project via lateral lemniscus to the inferior colliculi (tectum)
From inferior colliculi…
Axons then project to medial geniculate nuclei of thalamus
From thalamic neurons…
Project to primary auditory cortex
Lateral and maedial superior olives react to differences in what heard…
Medial: arrival time differences
Lateral: amplitude differences
Both lateral and medial project to…
Inferior colliculus :
Deep layers of inferior colliculus are lid out according to auditory space. Allowing location of sound sources in the world. The shallow layers are laid out retinoptopically
Auditory cortex located in
Temporal lobe
Core region or auditory cortex
Includes primary cortex
Belt of auditory cortex
Surrounds core region
Secondary cortex outside belt
Referred to as a parabelt areas
How many separate areas of secondary auditory cortex are thee in primates
10
A1 neurons
Sound frequency
Damage does not produce deafness
Impaired at defying a sequence of sounds (melody)
A2 (secondary auditory cortex) neurons
Best to complex combo of sounds
Two streams of auditory cortex
Anterior auditory pathway
Posterior auditory pathway
Auditory signals to two areas of association cortex
Prefrontal cortex
Prosterior partietal cortex
Anterior auditory pathway
Involved in identifying sounds (what)
Posterior auditory pathway
Involved in locating sounds (where)
Lesions of auditory cortex
Results in few permanent hearing deficits
Hinders sound localization and pitch discrimination
Total deafness..
Rare because multiple pathways
2 kinds:
Conductive deafness: damage to ossicles
Nerve deafness: damage to cochlea
