1. Peripheral Auditory Stimulus & Brain Activity
 Peripheral Auditory Path
This auditory path to the brain
includes:
1. Outer ear stimulus
2. Middle ear stimulus
3. Inner ear stimulus

2. Peripheral Auditory Stimulus & Brain Activity
 Peripheral Auditory Path
The stimulus “modifications” received
from each of these peripheral areas are
cumulative in nature.
Each modify the acoustic signal.

3. Peripheral Auditory Stimulus & Brain Activity
 Peripheral Auditory Path
Almost all of the peripheral auditory
mechanism is located in the temporal
bone.

4. Peripheral Auditory Stimulus & Brain Activity
 Peripheral Auditory Path
There is a temporal bone on for each
ear. It covers the temporal lobe area
of the brain.

5. Peripheral Auditory Stimulus & Brain Activity
 Outer Ear (Pinna) contribution
It “collects” acoustic information and
creates resonances of that acoustic
information, which are further
modified in the external auditory
meatus.

6. Peripheral Auditory Stimulus & Brain Activity
External Auditory Meatus (ear canal) contribution
The resonances collected by the pinna
result in a characteristic fundamental
resonant peak for each ear (usually around
2700Hz).

7. Peripheral Auditory Stimulus & Brain Activity
Tympanic membrane (eardrum) contribution
The TM has a surface area seventeen times
larger than the foot plate of the stapes at
the round window.
This creates an areal ratio, which when
coupled with the movement of the middle
ear bones, further modifies the received
acoustic signal.

8. Peripheral Auditory Stimulus & Brain Activity
The Ossicles (middle ear bones) contribution
This is the area where the sound becomes
“mechanically” amplified with the Class II
lever function.

9. Peripheral Auditory Stimulus & Brain Activity
The Ossicles (middle ear bones) contribution
This is also where the stapedial and tensor
tympani muscles are modified by efferent
information from the brain.
It is the first location in the acoustic path
which becomes modified with brain
activity.

10. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contributions
This is where the acoustic and
mechanical modifications are
“transduced” into fluid movement
(hydraulic) energy.

11. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contribution
This hydraulic movement of perilymph
fluid creates undulations of the basilar
membrane.
The Organ of Corti which contains the
inner and outer hair cells rests upon this
membrane.

12. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contribution
As the outer hair cells wave around,
they “sweep” against the tectorial
membrane.
This hair cell movement creates the
sixty decibel cochlear compressor
(2.5:1) amplifier.

13. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contribution
This is the next location where the
brain sends efferent information to
modify the performance of the
cochlear amplifier.

14. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contribution
This activity by the hair cells within
the Organ of Corti synapse (innervate)
the eighth cranial nerve (auditory
nerve).

15. Peripheral Auditory Stimulus & Brain Activity
 The Inner Ear contribution
The auditory (VIIIth) nerve
stimulation information begins the
afferent path to the cochlear nucleus
of each ear.

16. Peripheral Auditory Stimulus & Brain Activity
 Healthy Brain contribution
With healthy brain performance, the
afferent pathways of the auditory system
will now create reactionary activity and
contribute to good health for all systems
controlled by the brain.