Anatomy and Physiology of the Auditory System

Keypoints

  1. 1.
    The auditory system consists of four anatomically separate structures:
    1. (a)

      those that conduct the stimulus to the receptors

       
    2. (b)

      the receptors

       
    3. (c)

      the auditory nerve

       
    4. (d)

      the central auditory nervous system

       
     
  2. 2.

    The most important part regarding tinnitus is the auditory nervous system.

     
  3. 3.

    The auditory nervous system consists of two parallel ascending pathways that project to auditory cortices and two (reciprocal) descending pathways that project to nuclei of the auditory pathways.

     
  4. 4.

    The nuclei in the ascending auditory pathways process information in a serial hierarchical fashion, and processing occurs in modules with specific functions.

     
  5. 5.

    Two separate ascending sensory pathways have been identified in the auditory pathways: classical pathways and the non-classical pathways. Also, the somatosensory and visual pathways have two different ascending tracts.

     
  6. 6.

    The classical pathways are also known as the lemniscal system, or the specific system, and the non-classical pathways are also known as the extralemniscal system, or the unspecific system. The non-classical pathways have been divided into the defuse system and the polysensory pathways.

     
  7. 7.

    The classical and non-classical pathways process information differently and have different central targets, especially regarding connections to the thalamus and the cerebral cortex.

     
  8. 8.

    The non-classical ascending auditory pathways branch off the classical pathways at several levels, the most prominent being the central nucleus of the inferior colliculus.

     
  9. 9.

    The auditory pathways receive input from the somatosensory system at the external nucleus of the inferior colliculus and from the dorsal cochlear nucleus as well.

     
  10. 10.

    The auditory pathways are mainly crossed, but there are extensive connections between nuclei at the two sides at two levels: the pontine nuclei (superior ­olivary complex) and the midbrain level (inferior colliculus). There are also extensive ­connections between the two sides at the cerebral cortical level.

     
  11. 11.

    The auditory nerve sends collaterals to cells in all these divisions of the cochlear nucleus. That is the earliest sign of the anatomical basis for parallel processing of information. Parallel processing occurs throughout the ascending pathways by axons branching to connect to more than one group of nerve cells.

     
  12. 12.

    Descending auditory pathways are abundant, in particular, the cortico-thalamic pathways, but little is known about their function. The descending pathways are largely reciprocal to the ascending pathways. The descending pathways reach as far caudal as the receptors in the cochlea.

     
  13. 13.

    The classical sensory pathways are interrupted by synaptic contacts with neurons in the ventral parts of the thalamus, which project to the primary ­sensory cortices.

     
  14. 14.

    The non-classical sensory pathways use the dorsal and medial thalamus as relay, the neurons of which project to secondary and association cortices thus bypassing the primary sensory cortices.

     
  15. 15.

    Neurons in the dorsal and medial thalamus make direct (subcortical) connections with other parts of the CNS, such as structures of the limbic system, while the classical sensory systems connect to other parts of the CNS, mainly via association cortices.

     
  16. 16.

    There are anatomical connections between the upper spinal cord and the dorsal cochlear nucleus and between the caudal trigeminal nucleus and the dorsal cochlear nucleus. There are anatomical connections between the somatosensory system and midbrain nuclei of the non-classical auditory system.

     
  17. 17.

    Neurons in the nuclei of the classical pathways respond distinctly to specific sensory stimuli and have distinct frequency selectivity.

     
  18. 18.

    Sound stimulation may increase the firing rate of auditory nerve fibers, but saturation occurs for most fibers at low sound intensities.

     
  19. 19.

    Periodic sounds cause many nerve fibers to become locked to the waveform of the sound, and consequently, the firing of such fibers becomes time locked to each other. It subsequently causes the discharge of many neurons in the ascending auditory pathways, which then become time locked to each other.

     
  20. 20.

    Stream segregation implies that different types of information (for example, spatial and object information) are processed in anatomically different parts of the sensory nervous system.

     
  21. 21.

    Parallel processing allows the same information to be processed in anatomically different parts of the nervous system, while stream segregation implies that different kinds of information are processed in anatomically different structures.

     
  22. 22.

    Much less is known about the functional role of the non-classical pathways compared to the classical pathways, but neurons of the nuclei of the non-classical pathways respond less distinctly and are broader tuned than cells in the classical pathways and respond to a broad range of stimuli. They also integrate information on wider spatial scales than the classical pathways.

     
  23. 23.

    Neurons in the nuclei of the classical auditory pathways, up to and including the primary auditory cortex, respond only to one sensory modality (sound) while neurons of higher order cortices (secondary and association cortices) integrate information from several sensory systems and respond to different sensory modalities. This response can be modulated by input from non-sensory brain areas such as the amygdala.

     
  24. 24.

    Some neurons in the ascending non-classical pathways respond to more than one sensory modality. Their response to sound can be modulated by other sensory input.

     
  25. 25.

    The non-classical pathways make direct (subcortical) connections from the thalamus to other parts of the CNS, such as structures of the limbic s­ystem, while the classical sensory systems connect to other such parts of the CNS mainly via association cortices.

     
  26. 26.

    Stimulation of the somatosensory system affects perception of sounds in children, indicating involvement of the non-classical auditory system in children.

     
  27. 27.

    There are no signs of cross-modal interaction in adults, except with some forms of tinnitus and in autistic individuals, indicating that the non-classical auditory pathways are not normally active in adults.

     
  28. 28.

    Sensory systems connect to motor systems, the limbic system, reticular activating system, and the autonomic nervous system through subcortical and cortical routes.

     
  29. 29.

    There is considerable interaction between different systems in the brain, such as between different sensory systems and between sensory systems and non-sensory systems.

     

Keywords

Ear Auditory pathways Anatomy Non-classical pathways Physiology Cross-modal interaction 

Abbreviations

AAF

Anterior auditory (cortical) field

AES

Anterior ectosylvian sulcus area

AI

Primary auditory cortex

AII

Secondary auditory cortex

AN

Auditory nerve

AVCN

Anterior ventral cochlear nuclei

C2

Upper segment of the cervical spine

CN

Cochlear nucleus

COCB

Crossed olivocochlear bundle

DC

Dorsal cortex (of IC)

DNLL

Dorsal nucleus of the lateral lemniscus

DPOAE

Distortion product otoacoustic emission

DRG

Dorsal root ganglion

DZ

Dorsal auditory zone

ED

Posterior ectosylvian gyrus dorsal part

EI

Posterior ectosylvian

EV

Posterior ectosylvian gyrus

IC

Inferior colliculus

ICC

Central nucleus of the IC

ICX

External nucleus of the IC

IHC

Inner hair cells

In

Insular

LL

Lateral lemniscus

LSO

Lateral superior olive

MG

Medial geniculate body

MSO

Medial superior olive

NLL

Nucleus of the lateral lemniscus

NTB

Nucleus of the trapezoidal body

OCB

Olivocochlear bundle

OHC

Outer hair cells

PAF

Posterior auditory (cortical) field

PVCN

Posterior ventral cochlear nuclei

SH

Stria of Held (intermediate stria)

SM

Stria of Monakow (dorsal stria)

SOC

Superior olivary complex

SOE

Spontaneous otoacoustic emission

Sp5

Trigeminal nucleus

Te

Temporal cortex

TEOAE

Transient evoked otoacoustic emissions

UCOCB

Uncrossed olivocochlear bundle

Ve

Auditory cortex ventral area

VNLL

Ventral nucleus of the lateral lemniscus

VP

Auditory cortex ventral posterior area

References

  1. 1.
    Møller AR (2006) Hearing: anatomy, physiology, and disorders of the auditory system, 2nd ed. Amsterdam: Academic Press.Google Scholar
  2. 2.
    Shepherd GM (1994) Neurobiology. New York: Oxford University Press. 760.Google Scholar
  3. 3.
    Harrison RV and IM Hunter-Duvar, (1988) An anatomical tour of the cochlea, in Physiology of the ear, AF Jahn and J Santos-Sacchi, Editors. Raven Press: New York. 159–71Google Scholar
  4. 4.
    Møller AR (1988) Evoked potentials in intraoperative monitoring. Baltimore: Williams and Wilkins.Google Scholar
  5. 5.
    Møller AR (2003) Sensory systems: anatomy and physiology. Amsterdam: Academic Press.Google Scholar
  6. 6.
    Korsan-Bengtsen MM (1973) Distorted speech audiometry. Acta Otolaryng. Suppl. 310.Google Scholar
  7. 7.
    Aitkin LM (1986) The auditory midbrain, structure and function in the central auditory pathway. Clifton, NJ: Humana Press.Google Scholar
  8. 8.
    Aitkin LM, H Dickhaus, W Schult et al (1978) External nucleus of inferior colliculus: auditory and spinal somatosensory afferents and their interactions. J. Neurophysiol. 41:837–47.PubMedGoogle Scholar
  9. 9.
    Aitkin LM, CE Kenyon and P Philpott (1981) The representation of auditory and somatosensory systems in the external nucleus of the cat inferior colliculus. J. Comp. Neurol. 196:25–40.PubMedCrossRefGoogle Scholar
  10. 10.
    Jain R and S Shore (2006) External inferior colliculus integrates trigeminal and acoustic information: unit responses to trigeminal nucleus and acoustic stimulation in the guinea pig. Neurosci. Lett. 395:71–5.PubMedCrossRefGoogle Scholar
  11. 11.
    Zhou J and S Shore (2006) Convergence of spinal trigeminal and cochlear nucleus projections in the inferior colliculus of the guinea pig. J. Comp. Neurol. 495:100–12.PubMedCrossRefGoogle Scholar
  12. 12.
    Dehmel S, YL Cui and SE Shore (2008) Cross-modal interactions of auditory and somatic inputs in the brainstem and midbrain and their imbalance in tinnitus and deafness. Am. J. Audiol. 17:S193–209.PubMedCrossRefGoogle Scholar
  13. 13.
    LeDoux JE (1992) Brain mechanisms of emotion and emotional learning. Curr. Opin. Neurobiol. 2:191–7.PubMedCrossRefGoogle Scholar
  14. 14.
    Møller AR and P Rollins (2002) The non-classical auditory system is active in children but not in adults. Neurosci. Lett. 319:41–4.PubMedCrossRefGoogle Scholar
  15. 15.
    Møller AR, MB Møller and M Yokota (1992) Some forms of tinnitus may involve the extralemniscal auditory pathway. Laryngoscope 102:1165–71.PubMedCrossRefGoogle Scholar
  16. 16.
    Møller AR (2008) Neural plasticity: for good and bad. Progress of Theoretical Physics Supplement No 173:48–65.Google Scholar
  17. 17.
    Møller AR (2007) Neurophysiologic abnormalities in autism, in New autism research developments , BS Mesmere, Editor. Nova Science Publishers: New York.Google Scholar
  18. 18.
    Møller AR, JK Kern and B Grannemann (2005) Are the non-classical auditory pathways involved in autism and PDD? Neurol. Res. 27:625–9.PubMedCrossRefGoogle Scholar
  19. 19.
    Møller AR (2006) Neural plasticity and disorders of the nervous system. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
  20. 20.
    Pfaller K and J Arvidsson (1988) Central distribution of trigeminal and upper cervical primary afferents in the rat studied by anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin. J. Comp. Neurol. 268:91–108.PubMedCrossRefGoogle Scholar
  21. 21.
    Zhou J and S Shore (2004) Projections from the trigeminal nuclear complex to the cochlear nuclei: a retrograde and anterograde tracing study in the guinea pig. J. Neurosci. Res. 78:901–7.PubMedCrossRefGoogle Scholar
  22. 22.
    Kanold PO and ED Young (2001) Proprioceptive information from the pinna provides somatosensory input to cat dorsal cochlear nucleus. J. Neurosci. 21:7848–58.PubMedGoogle Scholar
  23. 23.
    Li H and N Mizuno (1997) Single neurons in the spinal trigeminal and dorsal column nuclei project to both the cochlear nucleus and the inferior colliculus by way of axon collaterals: a fluorescent retrograde double-labeling study in the rat. Neurosci. Res. 29:135–42.PubMedCrossRefGoogle Scholar
  24. 24.
    Shore SE, Z Vass, NL Wys et al (2000) Trigeminal ganglion innervates the auditory brainstem. J. Comp. Neurol. 419: 271–85.PubMedCrossRefGoogle Scholar
  25. 25.
    Itoh K, H Kamiya, A Mitani et al (1987) Direct projections from dorsal column nuclei and the spinal trigeminal nuclei to the cochlear nuclei in the cat. Brain Res. 400: 145–50.PubMedCrossRefGoogle Scholar
  26. 26.
    Young ED, I Nelken and RA Conley (1995) Somatosensory effects on neurons in dorsal cochlear nucleus. J. Neurophysiol. 73:743–65.PubMedGoogle Scholar
  27. 27.
    Zhan X, T Pongstaporn and DK Ryugo (2006) Projections of the second cervical dorsal root ganglion to the cochlear nucleus in rats. J. Comp. Neurol. 496:335–48.PubMedCrossRefGoogle Scholar
  28. 28.
    Shulman A (1987) External electrical tinnitus suppression: a review. Am. J. Otol. 8:479–84.PubMedGoogle Scholar
  29. 29.
    Vass Z, SE Shore, AL Nuttall et al (1997) Trigeminal ganglion innervation of the cochlea – a retrograde transport study. Neuroscience 79:605–15.PubMedCrossRefGoogle Scholar
  30. 30.
    Marsh RA, CD Grose, JJ Wenstrup et al (1999) A novel projection from the basolateral nucleus of the amygdala to the inferior colliculus in bats. Soc. Neurosci. Abstr. 25:1417.Google Scholar
  31. 31.
    Winer JA and CC Lee (2007) The distributed auditory cortex. Hear. Res. 229:3–13.PubMedCrossRefGoogle Scholar
  32. 32.
    Schucknecht HF (1974) Pathology of the ear. Cambridge, MA: Harvard University Press.Google Scholar
  33. 33.
    Pickles JO (1988) An Introduction to the physiology of hearing, 2nd ed. London: Academic Press.Google Scholar
  34. 34.
    Kim S, DR Frisina and RD Frisina (2002) Effects of age on contralateral suppression of distortion product otoacoustic emissions in human listeners with normal hearing. Audiol. Neurootol. 7:348–57.PubMedCrossRefGoogle Scholar
  35. 35.
    Büki B, P Avan and O Ribari (1996) The effect of body position on transient otoacoustic emission, in Intracranial and intralabyrinthine fluids, A Ernst, R Marchbanks and M Samii, Editors. Springer Verlag: Berlin. 175–81.CrossRefGoogle Scholar
  36. 36.
    Kiang NYS, T Watanabe, EC Thomas et al (1965) Discharge patterns of single fibers in the cat’s auditory nerve. Cambridge, MA: MIT Press.Google Scholar
  37. 37.
    Møller AR (1983) Frequency selectivity of phase-locking of complex sounds in the auditory nerve of the rat. Hear. Res. 11:267–84.PubMedCrossRefGoogle Scholar
  38. 38.
    Møller AR (1977) Frequency selectivity of single auditory nerve fibers in response to broadband noise stimuli. J. Acoust. Soc. Am. 62:135–42.PubMedCrossRefGoogle Scholar
  39. 39.
    Sellick PM, R Patuzzi and BM Johnstone (1982) Measurement of basilar membrane motion in the guinea pig using the Mossbauer technique. J. Acoust. Soc. Am. 72: 131–41.PubMedCrossRefGoogle Scholar
  40. 40.
    Guinan Jr. JJ, BE Norris and SS Guinan (1972) Single auditory units in the superior olivary complex. II. Location of unit categories and tonotopic organization. Int. J. Neurosci. 4:147–66.CrossRefGoogle Scholar
  41. 41.
    Møller AR (1974) Coding of sounds with rapidly varying spectrum in the cochlear nucleus. J. Acoust. Soc. Am. 55:631–40.PubMedCrossRefGoogle Scholar
  42. 42.
    Shore SE, H El Kashlan and J Lu (2003) Effects of trigeminal ganglion stimulation on unit activity of ventral cochlear nucleus neurons. Neuroscience 119:1085–101.PubMedCrossRefGoogle Scholar
  43. 43.
    Shore SE (2005) Multisensory integration in the dorsal cochlear nucleus: unit responses to acoustic and trigeminal ganglion stimulation. Eur. J. Neurosci. 21:3334–48.PubMedCrossRefGoogle Scholar
  44. 44.
    Shulman A, J Tonndorf and B Goldstein (1985) Electrical tinnitus control. Acta Otolaryngol. 99:318–25.PubMedCrossRefGoogle Scholar
  45. 45.
    Zhang J and Z Guan (2008) Modulatory effects of somatosensory electrical stimulation on neural activity of the dorsal cochlear nucleus of hamsters. J. Neurosci. Res. 86:1178–87.PubMedCrossRefGoogle Scholar
  46. 46.
    Zhang J and Z Guan (2007) Pathways involved in somatosensory electrical modulation of dorsal cochlear nucleus activity. Brain Res. 1184:121–31.PubMedCrossRefGoogle Scholar
  47. 47.
    Shore SE, S Koehler, M Oldakowski et al (2008) Dorsal cochlear nucleus responses to somatosensory stimulation are enhanced after noise-induced hearing loss. Eur. J. Neurosci. 27:155–68.PubMedCrossRefGoogle Scholar
  48. 48.
    Szczepaniak WS and AR Møller (1993) Interaction between auditory and somatosensory systems: a study of evoked potentials in the inferior colliculus. Electroencephologr. Clin. Neurophysiol. 88:508–15.CrossRefGoogle Scholar
  49. 49.
    Cacace AT, JP Cousins, SM Parnes et al (1999) Cutaneous-evoked tinnitus. II: review of neuroanatomical, physiological and functional imaging studies. Audiol. Neurotol. 4:258–68.CrossRefGoogle Scholar
  50. 50.
    Cacace AT, JP Cousins, SM Parnes et al (1999) Cutaneous-evoked tinnitus. I: phenomenology, psychophysics and ­functional imaging. Audiol. Neurotol. 4:247–57.CrossRefGoogle Scholar
  51. 51.
    Cacace AT, TJ Lovely, DJ McFarland et al (1994) Anomalous cross-modal plasticity following posterior fossa surgery: some speculations on gaze-evoked tinnitus. Hear. Res. 81:22–32.PubMedCrossRefGoogle Scholar
  52. 52.
    Hotta T and K Kameda (1963) Interactions between somatic and visual or auditory responses in the thalamus of the cat. Exp. Neurol. 8:1–13.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.School of Behavioral and Brain SciencesThe University of Texas at DallasRichardsonUSA

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