1 / 39

HST.722 Brain Mechanisms of Speech and Hearing Fall 2005 Dorsal Cochlear Nucleus September 14, 2005 Ken Hancock

HST.722 Brain Mechanisms of Speech and Hearing Fall 2005 Dorsal Cochlear Nucleus September 14, 2005 Ken Hancock. Dorsal Cochlear Nucleus (DCN). Overview of the cochlear nucleus and its subdivisions Anatomy of the DCN Physiology of the DCN Functional considerations.

afya
Download Presentation

HST.722 Brain Mechanisms of Speech and Hearing Fall 2005 Dorsal Cochlear Nucleus September 14, 2005 Ken Hancock

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HST.722 Brain Mechanisms of Speech and HearingFall 2005Dorsal Cochlear NucleusSeptember 14, 2005Ken Hancock

  2. Dorsal Cochlear Nucleus (DCN) • Overview of the cochlear nucleus and its subdivisions • Anatomy of the DCN • Physiology of the DCN • Functional considerations

  3. Dorsal Cochlear Nucleus (DCN) • Overview of the cochlear nucleus and its subdivisions • Anatomy of the DCN • Physiology of the DCN • Functional considerations

  4. DCN VCN AN The cochlear nucleus

  5. AN fibers terminate in a “tonotopic” or “cochleotopic” pattern DCN 36.0 kHz 10.2 kHz AVCN 2.7 kHz PVCN 0.17 kHz

  6. Spherical bushy Octopus Multipolar Globular bushy Major subdivisions of the cochlear nucleus

  7. SBC OA GBC MA Summary of pathways originating in the cochlear nucleus Inferior colliculus Lateral lemniscus Superior olive

  8. Projections suggest DCN is a different animal than VCN • (All roads lead to the inferior colliculus) • VCN projects directly to structures dealing with binaural hearing and olivocochlear feedback • DCN ???

  9. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • Physiology of the DCN • Functional considerations

  10. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • Physiology of the DCN • Functional considerations

  11. cartwheel granule stellate Somatosensory Auditory Vestibular golgi ? ? I.C. vertical fusiform giant D T auditory nerve Tzounopoulos 2004 Kanold Young 2001 DCN PVCN

  12. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • Functional considerations

  13. Eric Young Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • Functional considerations

  14. Response Map classification scheme ~ Auditory Nerve increasing inhibition Young 1984

  15. type II BF BF tone noise DCN: Vertical cells are type II and type III units type III • Narrow V-shaped region of excitation • No spontaneous activity • Tone response >> noise response • V-shaped region of excitation • Inhibitory sidebands Evidence: Antidromic stimulation (Young 1980)

  16. record from neuron • shock its axon recording electrode recording electrode stimulating electrode stimulating electrode Antidromic stimulation DCN fusiform vertical DAS giant VCN

  17. DCN: “Principal” cells are type III and type IV units type III type IV • Evidence: • Antidromic stimulation (Young 1980) • Intracellular recording and labeling • (Rhode et al. 1983, Ding et al. 1996) spont • “Island of excitation” & “Sea of inhibition” • BF rate-level curve inhibited at high levels • Noise rate-level curve ~ monotonic

  18. type II BF BF tone noise type IV vertical fusiform spont giant Neural circuitry underlying DCN physiology:type II units inhibit type IV units Young & Brownell 1976 “reciprocal” responses

  19. Cross-correlogram type IV firing rate given type II fires at t=0 inhibitory trough type II unit type IV unit Classic experiment: type II units inhibit type IV units • multiunit recording Voigt & Young (1980, 1990) Voigt & Young 1980,1990

  20. DCN physiology so far… IV ~ principal cells + II ~ vertical cells + auditory nerve • type II units inhibit type IV units • BUT this analysis based on pure-tone responses • what happens with more general stimuli???

  21. Notch noise stimuli spectrum level Upper Inhibitory Sideband Inhibition from type II units doesn’t account for everything Type IV unit response map • (DCN responses to broadband stimuli cannot be predicted from responses to tones: nonlinear) • Type II units do not respond to notch noise—whither the inhibition? • Response map has two inhibitory regions?

  22. Broadband noise Notch noise • strong AN input dominates • type IV response is excitatory level AN input to type IV unit • type IV loses greater portion of its excitatory input • WBI input dominates • type IV response is inhibitory level AN input to WBI frequency frequency DCN notch noise sensitivity due to wideband inhibition WBI Nelken & Young 1994

  23. broadly-tuned, onset-chopper units are found in the PVCN (Winter & Palmer 1995) • typically respond better to broadband noise than to tones DCN • such responses arise from radiate or stellate neurons (Smith & Rhode 1989) • stellate cells send axons dorsally into the DCN, thus called “D-stellate cells” (Oertel et al. 1990) • D-stellate cells are inhibitory (Doucet & Ryugo 1997) PVCN PVCN: is the D-stellate cell the wideband inhibitor?

  24. Summary: Circuitry of DCN deep layer Spirou and Young 1991 type II type II W.B.I. W.B.I. “reciprocal” response properties

  25. D Summary of DCN anatomy and physiology granule Nonauditory Somatosensory Auditory Vestibular • vertical cell • type II unit • narrowband inhibition • D-stellate cell • onset-chopper • wideband inhibition fusiform

  26. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • diverse response properties • complex interconnections • highly nonlinear • Functional considerations

  27. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • diverse response properties • complex interconnections • highly nonlinear • Functional considerations

  28. +15° 0° -15° “first notch” frequency changes with elevation Filtering by the pinna provides cues to sound source location “Head Related Transfer Function” (HRTF) Outer ear gain Geisler 1998

  29. vary notch freq Reiss & Young 2005 Physiology  May 2000 Behavior  Type IV units are sensitive to HRTF first notch • type IV units are inhibited by notches centered on BF • null in DCN population response may code for sound source location Young et al. 1992

  30. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • receives nonauditory inputs • has similar organization to cerebellar cortex • Physiology of the DCN • diverse response properties • complex interconnections • highly nonlinear • Functional considerations • coding sound source location based on pinna cues

  31. descending auditory somatosensory “plastic” synapses cochlea DCN is a “cerebellum-like structure” Generic cerebellum-like structure Bell 2001

  32. Synaptic plasticity: Long-Term Potentiation (LTP) • “Classical” LTP demonstration at the hippocampal CA3-CA1 synapse • LTP evoked by tetanic stimulation (mechanism involves NMDA receptors) Tzounopoulos 2004

  33. electric organ electric organ discharge (EOD) Electric fish provide clues to cerebellum-like function black ghost knifefish (Apteronotus albifrons) http://nelson.beckman.uiuc.edu/ • electrical activity detected by electric lateral line • afferent activity transmitted to electric lateral line lobe (ELL), analogous to DCN

  34. Electric fields provide information about nearby objects Larger animal (predators, other knifefish) Water flea (prey) Zakon 2003 • BUT the fish generates its own electric fields: • tail movements • ventilation • cerebellum-like ELL helps solve this problem Bell 2001

  35. What do cerebellum-like structures do??? • Subtract the expected input pattern from the actual input pattern to reveal unexpected or novel features of a stimulus. • DCN: pinna movement is expected to shift the first notch, independent of what the sound source is doing

  36. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • diverse response properties • complex interconnections • highly nonlinear • Functional considerations: the DCN may… • code sound source location based on pinna cues • extract novel components of response

  37. This makes no sense! Levine 1999 DCN may play a role in tinnitus • percept of noise, ringing, buzzing, etc. • affects up to 80% of the population • 1 in 200 are debilitated • (not voices in the head) • So why DCN? Because tinnitus… • involves plasticity • may involve somatosensory effects

  38. Dorsal Cochlear Nucleus • Overview of the cochlear nucleus and its subdivisions • DCN projections do not reveal its function • Anatomy of the DCN • more complex than other CN subdivisions • nonauditory inputs • similar organization to cerebellar cortex • Physiology of the DCN • diverse response properties • complex interconnections • highly nonlinear • Functional considerations: the DCN may… • code sound source location based on pinna cues • extract novel components of response • contribute to tinnitus

More Related