Lecture 5 Audition - pages.ucsd.edupages.ucsd.edu/~johnson/COGS17/17W20Lec5AudSlides.pdf · SGb SGc...
Transcript of Lecture 5 Audition - pages.ucsd.edupages.ucsd.edu/~johnson/COGS17/17W20Lec5AudSlides.pdf · SGb SGc...
Lecture5
Audition
Cogs17*UCSD
SoundWaves
Frequency =#Cycles/Second=Hz
6cycles/sec=6Hz
1second
Perspeed atwhichmoleculesofmedium(air)ossicillate
Frequency =#Cycles/Second=Hz
6000cycles/sec=6000Hz=6kHz
.001second
Perspeed atwhichmoleculesofmedium(air)ossicillate
Phase =placeincycleofcondensation&rarefaction
Peakofphase
Peakofphase
Troughofphase
Troughofphase
Amplitude =Distance agivenmoleculeofmedium(air)travelsduringitsosscillation
Ifdistance<xmeters=LowAmplitude(softsound)
Ifdistance>xmeters=HighAmplitude(loudsound)
AuditoryReception
AlsocalledTympanicMembrane
n
(HammerAnvil
Stirrup)
Ossicles
OVALWINDOWofCochlea
ofStirrup
ConvertlargevibrationsofbigTympanicMembraneintosmaller,butmorepowerfulvibrationsofOvalWindow
OvercomesIMPEDANCEMISMATCHAirmoleculesareeasytovibrate,butviscousCOCLEARFLUIDmolecules
inCochleamuchhardertovibrate
TheCochlea
TheCochlea
OrganofCorti
Cross-SectionofCochlea
BasilarMembraneFloorofmiddlechamber
&ofOrganofCorti,onwhichtheHairCells
(Receptors)sit
TectorialMembraneWithinmiddlechamber,TopofOrganofCorti
OrganofCorti
HairCellsAuditoryReceptors
StandbetweenTectorialMembrane
above,andBasilarMembrane
below.
AsmembranesvibrateCILLIA(hairs)are
bent>>releaseNT.
HairCells
Cillia
K+Gate
K+
TransductioninHairCellsisPotassium(K+)based(NoNa+)
K+
WhenCillia arebent,K+gatesarepulledopened
K+
CochlearFluidisrichinPotassium
K+GateK+Gate
K+
K+K+
K+K+
K+
HairCells
K+
K+
K+ K+
K+
K+
K+
K+
K+
K+K+
K+
K+
K+K+
K+
K+K+
K+K+
K+
HigherConcentrationofK+OUTSIDEcell>>soK+enters
ThischangeinpolarityopensCa++gates
Ca++in,Neurotransmitterout
...aGraded response
Frequency(Pitch)
Humanshearfrom20Hzto20,000Hz(or20kHz)
But,wemakeourmostdetaileddiscriminationbetweenfrequenciesupto~5kHz
Thepianokeyboardrangesfrom27.5Hzatlowend
to4,186Hz(~4.2kHz)athighend
CodingforFrequency
• PlaceCoding
• Temporal(Rate)Coding
PlaceCoding
PlaceCoding
APEX
BasilarMembrane
Narrow&Stiff Wide&Floppy
PlaceCoding
Narrow&Stiffresonates
toHIGH Frequencies
Wide&Floppyresonates
toLOW Frequencies
BasilarMembrane(Timelapseimageofoscillation)
PlaceCoding
ThemoretheBasilarMembrane
resonates,thefartheritmoves... ...themorethe
Cillia oftheHairCellsare
BENTagainstthe
TectorialMembrane...
...themoreNeurotransmittertheHairCellsrelease.
PlaceCoding
HIGH Frequenciesresonate
BASEofcochlea
LOW Frequenciesresonate
APEXofcochlea
So,itisDISTRIBUTIONofNTreleasealongBasilarMembrane
thatcodesforFrequency
PlaceCoding
High frequencysound=moreresponsefromBasethanApex
BasilarMembraneHighFrequencyLowFrequency
Base Apex
Low frequencysound=moreresponsefromApexthanBase
BasilarMembraneHighFrequencyLowFrequency
Base Apex
Mid frequencysound=moreresponsefromMid-Membrane
HighFrequencyLowFrequencyBase ApexBasilarMembrane
HairCells accomodate thiswithagraded response,respondingtorelativeamountsofvibrationalongBasilarMembrane
BUTHairCellscommunicatetoSpiralGanglions(whoseaxonsmakeuptheAuditoryNerve)
whichfireActionPotentials
RefractoryPeriodforActionPotentialslimithowfrequentlySpiralGanglionscanfire!
Maximum~1000/second
Inadditiontodifferent"places"resonatingmorethanothers,WHOLE BasilarMembranevibratesatrateofinput
(e.g.3000Hz>>3000oscillations/sec)
Sohowcantheycodefora3000Hztone?!!
TemporalCoding(RateCoding)
TemporalCoding(RateCoding)
ANSWER:NosingleGanglioncellcan!ButagroupofthemworkingtogetherCAN!!
3000Hztone
SpiralGanglions(ANFs)
SGa
SGb
SGc
SGd
SGe
AllrespondingtoSAMEHairCell
OverallresponsefromAuditoryNerve
ProducesVOLLEYSofactivityatrateofinput(3000/sec)
TemporalCoding(RateCoding)
VolleyPrinciple– DependsonGanglionsbeingPhaseLocked
SpiralGanglionsdonotjustfirewhen
theyareready,butarelockedtothe
PHASEofinput(onlyfire~PEAK)
Inthisway,AuditoryNerve
producesVOLLEYSofactivityatcorrectintervals
Localization - viaAmplitude differences
"HeadShadow"Headabsorbssomeof
soundenergy,sosoundislouderatearclosertosource.
WorksbestwithHigherFrequencies(shorterwavelengths)sincelowerfrequencies
passaroundhead,lesslikelytobeabsorbed.
High frequencysoundshaveshort wavelengths
Low frequencysoundshavelong wavelengths
Localization - viaPhase differences
Localization - viaPhase differences
NotePHASEdifferenceattwoearsSmall-headedanimalsdonotusephase,
sinceoftenambiguous
WorksbestwithLowerFrequencies(longerwavelengths)
Localization - viaTiming DifferencesAxonfrom
COCHLEARNUCLEUS
LeftEar
Axonfrom
COCHLEARNUCLEUS
RightEar
SuperiorOlive(Medulla)
EachCochlearNucleusaxonbranchestosynapseononeofmanySuperiorOlivecells
Localization - viaTiming DifferencesAxonfrom
COCHLEARNUCLEUS
LeftEar
Axonfrom
COCHLEARNUCLEUS
RightEar
SoundcametotheLEFT earfirst
SuperiorOlive(Medulla)
Localization - viaTiming DifferencesAxonfrom
COCHLEARNUCLEUS
LeftEar
Axonfrom
COCHLEARNUCLEUS
RightEar
SuperiorOlive(Medulla)
IfRIGHT sideofSuperiorOlivefires,soundcametotheLEFT earfirst
OnlywheninputfromBOTHearsconvergeswillSuperiorOlivefire
SoundcametotheLEFT earfirst
Localization – viaTiming DifferencesAxonfrom
COCHLEARNUCLEUS
LeftEar
Axonfrom
COCHLEARNUCLEUS
RightEar
SuperiorOlive(Medulla)
IfLEFT sideofSuperiorOlivefires,soundcametotheRIGHT earfirst
SoundcametotheRIGHT earfirst
Localization – viaTiming DifferencesAxonfrom
COCHLEARNUCLEUS
LeftEar
Axonfrom
COCHLEARNUCLEUS
RightEar
SuperiorOlive(Medulla)
IfMIDDLE ofSuperiorOlivefires,soundcametoBOTH earsatsametime
Soundreachesbothearsatsametime
AuditoryPathways
BeginwithHairCells(Receptors)inCochlea
HairCells– AuditoryReceptorsCochlea
OrganofCorti
HairCells– AuditoryReceptors
Inner HairCells Outer HairCells
SpiralGanglions
AxonsmakeupAuditoryNerve
CochlearNucleus(inMedulla)
“Divergent”Connection
1:8
“Convergent”Connection
20:1
SpiralGanglion
CochlearNucleus(inMedulla)
ForDetails
(e.g.DiffFreqs)
NOT forDetails
(e.g.Amp)
AuditoryPathways
AuditoryNerveto
CochlearNucleusin
Medulla
Monaurali.e.eachAuditoryNerve
connects onlytoIPSI-lateralside
CochlearNucleusCells
SpiralGanglion(ANF)
Primary-Like
Build-Up
Onset
Phaser
CellRe
spon
se
CellRe
spon
seCe
llRe
spon
seCe
llRe
spon
se
Time
Time
Time
Time
Time
CellRe
spon
se
EachSpiralGanglionsynapsesonmultipleCochlearNucleusCells
AuditoryPathways
FibersfromCochlearNucleusgotoIPSI-lateraland CONTRA-lateralSuperiorOlivesinCerebellum
Thus,these,andallsubsequentconnections,
areBinaural
Combininginfofromboth earsallowsforlocalization.
AuditoryPathways
...isinputtoSuperiorOlivelocalizationcircuit
Onset signalfromCochlearNucleus...
AuditoryPathways
FromSuperiorOlives,
connecttoInferiorColliculi
inMidbrain
Thesecommunicatew/SuperiorColliculi(visualmotionmaps)
andTegmentum,todirecteyestosourceofsound
AuditoryPathwaysFromInferiorColliculi to
MedialGeniculateNucleus(MGN)
ofThalamus
MGNMedialGeniculateNucleus
MNEMONICS:NucleioftheThalamus
• LGN (LateralGeniculateNucleus)
• MGN (MedialGeniculateNucleus)
• VPN (VentralPosteriorNucleus)
• DMN (DorsalMedialNucleus)
• VLN (Ventro LateralNucleus)
• MDN (MedialDorsalNucleus)
• L isforLight(Visual)
• M isforMusic(Auditory)
• VP isforVeryPersonal(Touch)
• DM isforDogMuzzle(Smell)
• VL isforVictoryLap(Motor)
• MD isforMemoryDoctor(Memory)
Others?!
TopologicalMapsinAuditorySystemHighfrequency
soundBasilarMembrane
HighFrequencyLowFrequency
DistributionofactivityacrosstheBasilarMembrane(“Place-coded”frequency)ispreservedupthepathway
(Cochlea)
CochlearNucleus
HighFrequencyLowFrequency
(Medulla)
SuperiorOlive
HighFrequencyLowFrequency
(Medulla)
InferiorColliculus
HighFrequencyLowFrequency
(Midbrain)
MGN
HighFrequencyLowFrequency
(Thalamus)
A1
HighFrequencyLowFrequency
(Cortex)
SpiralGanglion
HighFrequencyLowFrequency
(Cochlea)
IntheAuditorysystem,suchTopologicalmaps
arecalled"Tonotopic Maps"
AuditoryPathways
FromMGNtoA1(PrimaryProjectionArea)
inMedialTemporalCortex
AuditoryCortex
PrimaryProjectionAreaforAudition
OnMedialfaceofTemporalLobe,inLateralFissure
A1 – PrimaryProjectionAreaforAuditioninCortex
500Hz,HighAmp
500Hz,LowAmp
TopologicalFrequencyMapAlsomappedper
Amplitude
1600Hz,HighAmpAllcellsineachcolumn
(through6layers,beloweachdot)havesamepreferredstimulus
A2 – SecondaryAuditoryCortex
A1
A1 – Respondsbesttosinglefrequency
A2 – Respondsbesttochangingfrequency
A2
Wernicke’sArea
HigherAuditoryCortex
Wernicke’sArea– SpecializedforcomprehendingSPEECH
InteractswithBroca's AreainPrefrontalCortex,forspeechProduction