Chapter 9- Sensation and Perception

ear anatomy

sound wave

fluctuations in air pressure across time caused by vibrations of objects in the environment

amplitude

intensity or magnitude of displacement of a pressure wave

dB

units measuring amplitude

loudness

psychological aspect of sound related to perceived intensity 

frequency

number of times per second that a pattern of pressure change repeats

Hz

unit measure frequency of sound

pitch

psychological aspect of sound related to perceived frequency

white noise

all audible frequencies at equal amounts

audibility threshold

lowest sound pressure level that can be reliably directed at a given frequency

outer ear

external portion of ear that collects and focuses sound waves

pinna

outer, funnel like part

ear canal

conducts sound vibrations from pinna to tympanic membrane

tympanic membrane

eardrum at the end of the ear canal that vibrates in the response to sound

middle ear

transfers and amplifies sound from tympanic membrane to the oval window

ossicles

3 tiny bones, malleus, incus, stapes

malleus

receives vibrations from tympanic membrane

incus

connects malleus to stapes

stapes

transmits sounds to oval window

oval window

flexible opening to cochlea where stapes transmits vibration to the fluid inside

inner ear

converts sound vibrations into neural signals

cochlea

tiny, coiled structure where sound is transduced in the organ of corti to the auditory nerve

organ of corti

structure of the basilar membrane that is composed of hair cells and auditory nerve fibers

basilar membrane

plate of fibers that forms the base of the cochlea

auditory nerve

a collection of neurons that convey information from hair cells in the cochlea to the brainstem

hair cell

cell that transduces mechanical movement in the inner ear to neural activity sent to the brain 

stereocilia

hairlike extensions on tips of hair cells that initiate release of neurotransmitters when bent

place code

info about where a sound waves frequency is coded by the place along the cochlea that has the highest mechanical movement 

temporal code

info about sound waves frequency is coded by the timing of neural firing as it releases to the period of the sound

ear, brainstem, thalamus, cortex

neural pathway

brainstem

cochlear nuclei, superior olive, inferior colliculus

cochlear nuclei

first brainstem nucleus where auditory nerve synapses

superior olive

brainstem region where inputs from both ears converge

inferior colliculus 

midbrain nucleus in the auditory pathway, relays info from the lower brainstem to the thalamus and auditory cortex

medial geniculate nucleus (MGN)

part of the thalamus that relays auditory signals to the temporal cortex

primary auditory cortex (A1)

responsible for processing basic acoustic info in the temporal lobe

secondary auditory complex (A2)

gets input from A1 and responds to more complex characteristics of sounds

tonotonic organization

neurons are organized anatomically in order of frequency

conductive hearing loss

hearing loss caused by problems with the outer or inner ear that causes issues with sound amplification

sensioneural hearing loss

hearing loss caused by defects in cochlea or auditory nerve that causes problems with sound transduction

cochlear implant

delivers sound directly to the auditory nerve

presbycusis

normal age related hearing loss

ear infection

middle ear is filled with fluids, impacting amplification of sound

excessive noise exposure

caused by damage to hair cells from repeated exposure to intense sounds