A DISCUSSION ON A DISCUSSION ON ENCODING OF ENCODING OF

AUDITORY INFORMATIONAUDITORY INFORMATION

KEMU ‘12-’17KEMU ‘12-’17

► ATIA HAROON(21):RELEASE OF SYNAPTIC ATIA HAROON(21):RELEASE OF SYNAPTIC TRANSMITTERTRANSMITTER

► AYESHA ABBASI(22):PLACE PRINCIPLE OF AYESHA ABBASI(22):PLACE PRINCIPLE OF FREQUENCY DISCRIMINATIONFREQUENCY DISCRIMINATION

► AYESHA AKHTAR(23):ENCODING OF AYESHA AKHTAR(23):ENCODING OF FREQUENCY AND VOLLEY PRINCIPLEFREQUENCY AND VOLLEY PRINCIPLE

► AYESHA AMTUL HASEEB(24):ENCODING OF AYESHA AMTUL HASEEB(24):ENCODING OF INTENSITYINTENSITY

► AYESHA HASSAN(25):INHIBITORY AYESHA HASSAN(25):INHIBITORY INNERVATIONSINNERVATIONS

A BRIEF DESCRIPTION OF INNER A BRIEF DESCRIPTION OF INNER EAREAR

►CochleaCochlea►Utricle Utricle ►SacculeSaccule►Semicircular canalsSemicircular canals

STRUCTURE OF COCHLEASTRUCTURE OF COCHLEA

THEORIES EXPLAINING THE THEORIES EXPLAINING THE APPRECIATION OF DIFFERENT APPRECIATION OF DIFFERENT

FREQUENCIES OF SOUNDSFREQUENCIES OF SOUNDS► FIRST GROUP: FIRST GROUP:

Analysis of sound frequency is a function of Analysis of sound frequency is a function of cerebral cortex and cochlea merely cerebral cortex and cochlea merely transmits the sound.transmits the sound.

TELEPHONE THEORY OF RUTHERFORDTELEPHONE THEORY OF RUTHERFORD

VOLLEY THEORYVOLLEY THEORY SECOND GROUP:SECOND GROUP:

Frequency analysis is done by cochlea,which Frequency analysis is done by cochlea,which sends the information to the cerebral cortex.sends the information to the cerebral cortex.

► RESONANCE THEORY OF HELMHOLTZRESONANCE THEORY OF HELMHOLTZ► PLACE THEORYPLACE THEORY

PLACE PRINCIPLE OF PLACE PRINCIPLE OF FREQUENCY DISCRIMINATIONFREQUENCY DISCRIMINATION

It states that the perception 0f sound depends It states that the perception 0f sound depends on where each component frequency produces on where each component frequency produces vibrations along the basilar membrane.vibrations along the basilar membrane.

CONCEPT OF RESONANACE POINT:CONCEPT OF RESONANACE POINT:That point on the basilar membrane which is That point on the basilar membrane which is

most strongly activated/stimulated by a most strongly activated/stimulated by a travelling wave.travelling wave.

Distance between stapes and resonance Distance between stapes and resonance point is inversel proportional to the point is inversel proportional to the frequency of sound waves .frequency of sound waves .

ll► high frequency sounds cause maximal high frequency sounds cause maximal

activation of basilar membrane near activation of basilar membrane near the base of cochlea.(close to oval the base of cochlea.(close to oval window and stapes)window and stapes)

► Low frequency: Low frequency: at apex of at apex of cochlea(helicotrema)cochlea(helicotrema)

► Intermediate frequency sounds:Intermediate frequency sounds: in in between two extremes between two extremes

BASIS OF PLACE PRINCIPLEBASIS OF PLACE PRINCIPLE

STRUCTURE OF BASILAR MEMBRANE:STRUCTURE OF BASILAR MEMBRANE:

20000_30000 basilar fibres projecting from 20000_30000 basilar fibres projecting from modiolus toward outer wall.modiolus toward outer wall.

Basal end_fixed at modiolusBasal end_fixed at modiolus

Distal end_embedded in basilar membrane.Distal end_embedded in basilar membrane.

AT BASEAT BASE: basilar membrane : basilar membrane stiff stiff due to due to thick, short reed like fibresthick, short reed like fibres

AT APEX:AT APEX:basilar membrane basilar membrane compliantcompliant due due to to thin,long fibresthin,long fibres

EXPERIMENTAL EVIDENCE EXPERIMENTAL EVIDENCE SUPPORTING PLACE THEORYSUPPORTING PLACE THEORY

► Long exposure to loud noise of a particular Long exposure to loud noise of a particular frequency destroys a specific portion of frequency destroys a specific portion of organ of corti.organ of corti.

► In In high tone deafness,high tone deafness, organ of corti near organ of corti near base of cochlea or nerve supplying cochlea base of cochlea or nerve supplying cochlea near base degenerates.near base degenerates.

►During exposure to high frequency During exposure to high frequency sound,cochlear microphone potentials show sound,cochlear microphone potentials show greater voltage in hair cells near base of greater voltage in hair cells near base of cochlea.cochlea.

► There is point to point representation of There is point to point representation of basilar membrane in auditory cortex.basilar membrane in auditory cortex.