Hearing 5: Auditory encoding & Hearing impairment

Question 1

Define Auditory Discrimination.

Answer 1

Auditory Discrimination:
The ability of the auditory system to discriminate sound based on:
Frequency
Intensity
Localization
Tonal and sequential pattern of sound

Question 2

Explain the Place Principle in determining sound frequency.

Answer 2

Place Principle:
Sound waves produce peak depression and maximum receptor stimulation at a specific place on the basilar membrane.
The distance between this point and the stapes is inversely related to the frequency of the sound.
Hair cells at different places are tuned to different frequencies due to differences in their stereocilia and biophysical properties.

Question 3

Describe Tonotopic Organization in the auditory pathway.

Answer 3

Tonotopic Organization:
Spatial organization of neurons in the auditory pathway from the cochlea to the cerebral cortex.
Neurons responding to low-frequency sounds are located at one end, while those responding to high frequencies are at the opposite end.
Auditory cortex maintains topographic localization of sound.

Question 4

How is sound intensity (loudness) determined in the auditory system?

Answer 4

Determining Sound Intensity:
Increased intensity results in:
Increased frequency of firing in the auditory nerve.
Vibration of a larger portion of the basilar membrane, activating more auditory nerve fibers.
Stimulation of outer hair cells when basilar membrane vibration reaches high intensity, signaling to the nervous system that the sound is loud.

Question 5

What factors determine sound localization in the auditory system?

Answer 5

Determining Sound Localization:
Intensity difference: Slightly more intense sound in the ear near the source than in the remote ear.
Phase (time) difference in sound waves reaching two ears (at low frequencies).
Pinnae of the two ears aid in discriminating the source of sound.

Question 6

How does the auditory cortex determine sound patterns?

Answer 6

Determining Sound Patterns:
Auditory cortex recognizes combinations or sequences of tones in a specific pattern.
Lesions of the auditory cortex may result in an inability to recognize sequential patterns of sound, such as in music, but do not impair the ability to discriminate frequency.

Question 7

Differentiate between Low, High, and Intermediate frequencies in the cochlea.

Answer 7

Frequency Discrimination:
Low frequency: Maximal stimulation at the apex.
High frequency: Maximal stimulation at the base.
Intermediate frequencies: Maximal stimulation at intermediate distances.

Question 8

Define Tinnitus and Deafness.

Answer 8

Tinnitus:
Ringing sensation caused by irritative stimulation of either the inner ear or vestibulocochlear.
Deafness:
Inability to hear sounds.

Question 9

Differentiate between Conduction Deafness and Nerve Deafness.

Answer 9

Conduction Deafness:
Defect in sound transmission to the inner ear.
Due to defects in the external or middle ear.
Nerve Deafness:
Defects in either the inner ear or vestibulocochlear nerve.
Lesions in the CNS are not clinically found due to redundancy and the bilateral nature of central auditory pathways.