Chapter 9.3 Phase locking, temporal code, rate saturation

Question 1

Rate Saturation

Answer 1

Occurs when a neuron’s firing rate reaches a maximum, and increasing the stimulus intensity no longer increases the neuron’s response.

Question 2

What do AN fibres fire in response to?

Answer 2

Displacement of stereocilia on hair cells

Question 3

Why does steroicllia not bend in response to a 20dB tone at 1000Hz?

Answer 3

The stereocilia on the hair cell feeding the auditory nerve (AN) fiber may not bend at all in response to a 20 dB tone at 1000 Hz because the intensity of the tone is too low to generate enough mechanical force to stimulate the hair cell and cause the stereocilia to bend

Question 4

How does the rate of neural firing in an AN Fiber change when energy is introduced from nearby frequencies?

Answer 4

The rate of neural firing for the first tone decreases, which is known as two-tone suppression, when a second tone of slightly different frequency is added.

Question 5

For moderately intense sounds, why can’t the brain rely on a single AN fiber to determine the frequency of the tone?

Answer 5

The sound waves may fall within the saturation range of an individual AN fiber, causing it to lose its ability to accurately represent the frequency information of the sound.

Question 6

Rate intensity Functions:

Answer 6

Graph plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities

Question 7

What are low-spontaneous fibers?

Answer 7

Low-spontaneous fibers are nerve fibers that have a low rate of spontaneous firing, typically less than 10 spikes per second.

Question 8

Low spontaneous firing rates Function

Answer 8

Good at detecting slow changes in sounds, such as low-pitched noises or soft sounds that change slowly over time. They require relatively intense sound before they will fire at higher rates.

Question 9

What are high-spontaneous fibers?

Answer 9

Nerve fibers that have a high rate of spontaneous firing, typically more than 30 spikes per second.

Question 10

How are high spontaneous fibers analogous to rods in the retina?

Answer 10

As they are responsible for detecting fast changes in sounds, such as high-pitched noises or sudden, sharp sounds that change quickly. They can increase their firing rate in response to relatively low levels of sound.

Question 11

What are mid-spontaneous fibers?

Answer 11

Mid-spontaneous fibers are nerve fibers that have a moderate rate of spontaneous firing, typically between 10 to 30 spikes per second. They are intermediate between low-spontaneous and high-spontaneous fibers.

Question 12

What is the common trait of both rods and high-spontaneous AN fibers?

Answer 12

Both rods and high-spontaneous AN fibers are highly sensitive to changes in their respective stimuli.

Question 13

What aspect of sensory input may not be provided by rods and high-spontaneous AN fibers?

Answer 13

Rods may not provide detailed information about color, while high-spontaneous AN fibers may not provide detailed information about frequency/pitch.

Question 14

How does the auditory system determine the frequency of sound waves?

Answer 14

The auditory system uses many different auditory nerve (AN) fibers with different spontaneous rates to accurately determine the frequency of sound waves. These AN fibers send signals to the brain based on how fast they fire in response to sound.

Question 15

How is the auditory system’s process similar to the visual system?

Answer 15

The auditory system’s process of determining sound frequency is similar to how our visual system uses different types of cones in our eyes to determine the wavelength of light

Question 16

Phase locking

Answer 16

When the firing of auditory nerve fibers is synchronized with the phase of a sound wave

Question 17

Why does phase locking occur?

Answer 17

Nerve fibers in the inner ear fire in response to the movement of hair cells’ stereocilia in one direction but not in the other, allowing the brain to accurately encode the timing or phase of incoming sound waves.

Question 18

Temporal Code

Answer 18

Refers to how the precise timing or phase of nerve cell firing in response to sound waves conveys information about the frequency or pitch of the sound.

Question 19

Why does temporal coding become inconsistent for higher frequency sounds in the auditory system?

Answer 19

It becomes inconsistent for higher frequency sounds above 1,000 Hertz because the refractory period of auditory nerve (AN) fibers prevents them from firing action potentials quickly enough to keep up with every cycle of the sound.

Question 20

What is the “volley principle” in the context of auditory processing?

Answer 20

Refers to multiple neurons in the auditory system working together as a group, “taking turns” to fire in response to high frequency sounds, allowing them to accurately encode the sound’s frequency and temporal pattern.