עבוד אותות במערכת החושיםסמסטר א' תשס"ח

5הרצאה מס' http://www.eng.tau.ac.il/~mira/Senses2008

Neural Activity

IHC and OHC Afferent innervation pattern

IHC Efferent Innervation

Lateral olivary complex fibers synapse on type I afferents coming from IHC

Afferent fibers synapse with brain stem at the cochlear nuclei

Action Potentials

Neural Activity:

Spontaneous Neural Activity (1)

Stationary

Spontaneous Neural Activity (2)

Correlation

Spontaneous Neural Activity (3)

Spontaneous Neural Activity (4)

The spontaneous neural activity can be described as:

• A stationary, renewal process.• The length of successive intervals are statistically

independent.

Thus• The probability density function of interval length describes

the process

Spontaneous Neural Activity (5)

Tn eT!n

1np

ep

- Interval lengthn – number of spikes in the interval T

Spontaneous Rate

Spontaneous Rate

Neural Activity:Response to Click

Neural Activity:Response to Click

Neural Activity:Response to a Tone

Tuning Curves

Tuning Curves

Neural Response as a function of Level

This figure shows the input-output function of a single fiber. Notice that the firing rate of the neuron increases as the stimulus intensity increases within its dynamic range, and eventually plateaus.

Input-Output Function of a Single Auditory Nerve Fiber

In general, the auditory nerve fibers that have higher levels of spontaneous activity (HSR), have lower thresholds and lower saturation points.

The fibers that have lower levels of spontaneous acitivity (LSR), have higher thresholds and higher saturation points

threshold

saturation

Auditory nerve rate-intensity functions

Neural Activity:Response to Speech