The Sense of Hearing Exam 2

Low spontaneous rate (less the 0.5 spikes per sec ((sps)))

high threshold

Medium spontaneous rate 0.5-18 sps

medium threshold

High/greater than 18 sps

low threshold

Tuning curve/Iso-rate function

finds level that produces the same firing rate at different frequencies

Tuning curve/Iso-rate function records:

level resulting in a criterion increase in the firing rate

Why different slopes for tuning curve/iso-rate function?

the traveling wave has a steeper slope on the low frequency side and a shallower slope on the high frequency side due to the BM non-symmetry

Neural excitation pattern records

the firing rate from a sample of the neural population

Is the auditory nerve linear or non-linear

non-linear

Does a rarefaction click have excitatory or inhibitory first

excitatory, so it has an earlier response

Does a condensation click have excitatory or inhibitory first

inhibitory, so it takes longer to respond

Post-stimulus histogram

histograms of the times at which neurons fire

Synchrony suppression

fiber fires in synchrony with the tone on fewer periods when a second tone is added to the first

Neural Spectrum represents:

the firing pattern of the population of fibers

Neural rate is saturate for ____ and ____ levels when the population of neural fibers is assessed

moderate and high

Spectral peaks are preserved in units with ____ spontaneous rates

low

the Central Auditory nervous system is comprised of:

tracts: pathways

nuclei: collection of cells bodies

Order of fibers: Auditory nerve

1st order or primary fibers

Order of fibers: Cochlear nucleus

2nd order

Order of the fibers: Beyond the cochlear nucleus

main tracts or pathways represented binaurally

Contralateral

opposite sides of the body

Ipsilateral

the same side of the body

80% of fibers cross over to the ____ pathway

contralateral

20% of fibers cross over to the ____ pathway

ipsilateral

First place with binaural representation of sound:

Superior Olivary Complex

The Superior Olivary complex helps with sound ____

localization

LSO:

lateral superior olive

MSO:

medial superior olive

The majority of the neurons in the LSO have ____ frequency CF’s

high

The majority of the neurons in the MSO have ____ frequency CF’s

low

Does the LSO have EI or EE cells?

EI

What do EI cells code for?

level (intensity) differences between ears

Does the MSO have EI or EE cells?

EE cells

What do EE cells code for?

phase (time) differences between ears

The Characteristic delay:

helps the brain know where sound originates (two boats and plane example)

LSO Dominant animal head size

small

MSO Dominant animal head size

large

Superior olive two reflexes:

blink and acoustic reflex

Blink reflex

eye blinks in response to an intense sound

Acoustic reflex

contraction of the stapedius muscle in response to an intense sound

How does the stapedius muscle contract?

bilaterally and perpendicular to the primary rotary axis

The stapedius muscle contracts when/during:

• presence of loud sounds

• prior to and during vocalization

• randomly and intermittently

• voluntarily (for some people)

What does the stapedius muscle’s contraction do to the middle ear?

stiffens it

3 Stapedius Muscle Theories

intensity control, ossicular chain fixation, and perceptual theory

Stapedius Muscle: intensity control

protection from loud sounds.

probably not valid because it attenuates low frequencies and high frequencies are the ones that cause damage. There are no naturally loud sounds with a long duration in nature so no evolutionary reason.

Stapedius Muscle: ossicular fixation

holds ossicles in place

Stapedius Muscle: Perceptual theory

reduces physiological noise.

helps animals assess whether a sound is coming from inside or outside of the body (not in humans)

Inferior Colliculus role:

combine information from different processes that occur in the lower brainstem, startle reflex

Startle reflex/Moro’s response

response of an infant (contraction of the limb and neck muscles) when allowed to drop a short distance through the air or when startled by a sudden intense sound, goes away at 4-5 months

Absence of Startle reflex/Moro’s response at birth

may have a broken collar bone or damage to the spine

Auditory cortex location:

sylvian fissure. both cochleas supply input to each auditory cortex

Physiology of the cortex: ____ organization

tonotopic

McGurk effect

auditory /ba/ and visual /ga/ leads to /da/

Human studies of brain damage if above cochlear nucleus

no hearing loss, but stroke victims may have peripheral hearing loss

Parts of brain involved in processing music

cerebellum, prefrontal cortex, and auditory cortex

significance of the lateral lemniscus

when assessing infant hearing there is a highly myelinated pathway that gives a big response, which is at the lateral lemniscus

intensity:

dB level

Phase locking is a property of VIIIth nerve neurons for frequencies less than

4000 Hz

human stapedius muscle attenuates

low frequencies

What is plotted on the Y axis of a rate-intensity function?

firing rate (sps)

What is plotted on the X axis of a rate-intensity function?

level (dB)

What is plotted on the Y axis of a tuning curve?

level (dB)

What is plotted on the x axis of a tuning curve?

frequency (Hz)