CHAPTER 15Central Nervous System StructuresPowerPoint PresentationMajor Components of the Central Auditory Nervous System (CANS)Mid-Saggital View of BrainSlide 6Slide 7Slide 8Slide 9Neural Web-SitesSection Thru Brainstem Shows Cochlear NucleusThe Superior Olivary ComplexConnections To the Superior Olivary ComplexSuperior Olivary Processing Supports LocalizationDorsal (back) Side of BrainstemInferior ColliculusThalamus in PurpleAuditory Radiations ConnectLateral-Superior view of brainPrimary Auditory Cortex (AI): superior surface of the temporal lobe6 Cortical LayersCortical NeuronsCortical ProcessingCerebral Dominance/LateralityNeurophysiological MeasuresAuditory Evoked PotentialsExamples of AEP EpochsAuditory Brainstem ResponseGENERATORS of ABR WAVESThe Acoustic ReflexCHAPTER 15Central Auditory Nervous SystemCentral Nervous System Structures•Nucleus = a group of nerve cell bodies•Fiber Tract = a group of axonsMajor Components of the Central Auditory Nervous System (CANS)•VIIIth cranial nerve•Cochlear Nucleus•Superior Olivary Complex•Lateral Lemniscus•Inferior Colliculus•Medial Geniculate Body•Primary Auditory CortexBrainstemThalamusMid-brainTemporal Lobe<Trapezoid Body>Mid-Saggital View of BrainPonsCerebellum4th VentricleThalamusCorpus Callosum•MedGen Body•Inf Coll •Lat Lemn•SOC•Coch Nuc•VIIIth CNNeural Web-Siteshttp://rprcsgi.rprc.washington.edu/neuronames/hierarchy.htmlhttp://www.ets.uidaho.edu/med532/start.htmSection Thru Brainstem Shows Cochlear NucleusThe Superior Olivary ComplexConnections To the Superior Olivary ComplexSuperior Olivary Processing Supports Localization•Lateral SO-- Interaural Intensity Differences•Medial SO-- Interaural Time Differences(These are the two primary acoustic cues for localizing sounds)Dorsal (back) Side of Brainstem•Thalamus(medial geniculate)•Inferior Colliculus•4th Ventricle•Area of PonsInferior ColliculusThalamus in PurpleAuditory Radiations Connect•Medial Geniculate Body (in purple)to•Primary Auditory Cortex (in blue)Lateral-Superior view of brainPrimary Auditory Cortex (AI):superior surface of the temporal lobe6 Cortical Layers•Thalamic inputs >IV•project to pyramidal cells in layer III•Divergence from III–within AI–other cortical areas–contra AI•V and VI >>thalamus &ICCortical Neurons•Tonotopically and Spatiotopically organized•Highly Adaptable•Sensitive to CHANGES in Frequency and Intensity–Coding virtual pitch–demodulating complex signals (e.g. speech)Cortical Processing•Pattern Recognition•Duration Discrimination•Localization of Sounds•Selective AttentionCerebral Dominance/Laterality•Language Processing in the left hemisphere.(Remember the right ear has the strongest connections to the left hemisphere)•Most people show a right-ear advantage in processing linguistic stimuliNeurophysiological Measures•Gross Evoked Potentials-- Voltage changes in response to auditory stimulation recorded from the scalp•Single-Unit Measures-- Voltage (or other) changes recorded within a neuronAuditory Evoked Potentials•Recorded in different time intervals (“epochs”) following a sound•Earlier epochs come from lower in the system•Later epochs come from higher in the systemExamples of AEP Epochs•Electrocochleography-- within 5 milliseconds•Auditory Brainstem Response-- thru 10 ms•Middle Latency Response-- thru 75 ms •Auditory Late Response-- thru 200 msAuditory Brainstem ResponseTime (ms)Amplitude (V) Wave V LatencyIIIIIIIVVAmp V 010GENERATORS of ABR WAVESIIIIIIIVV=Distal VIIIth nerve=Medial VIIIth nerve=Cochlear Nucleus=Superior Olivary Complex=Lateral Lemniscus & Inferior ColliculusThe Acoustic ReflexAfferent:•VIIIth nerve•Cochlear Nucleus•Superior Olivary ComplexEfferent:•VIIth nerve nucleus•VIIth nerve•Stapedius