MEDS 371 Auditory system II hindbrain Dr Duck

MEDS 371 Auditory system II: hindbrain Dr. Duck O. Kim

cat brain dissected showing auditory system cerebellum auditory cortex inferior colliculus medial geniculate cochlear nucleus Oliver auditory nerve

h cat CN dorsal DCN anterior h AVCN tonotopic organization of CN CN: cochlear nucleus DCN: dorsal CN PVCN AVCN: anterovent. CN h PVCN: posterovent. CN Arnesen & Osen, 1978

type I (95%) 1. spherical bushy cell; AVCN 2. stellate cell; VCN 3. globular bushy cell; AVCN 4. octopus cell; PVCN 5. fusiform cell; DCN Kiang, 1975

cells in the cochlear nucleus PST histogram F O PST histogram GB spiral ganglion neuron type I (95%) S SB Kiang, 1975

end bulbs of Held at bushy cells of the AVCN Ryugo, 1999, Fig-10

intrinsic properties EPSPs cochlear nucleus neurons intracellular recording in brain-slice preparation Oertel et al. , 1988

The "where-processing" of sound: Neural representation of auditory space requires de novo computation unlike the retinotopic map.

Kim, Bishop, Kuwada, 2010 head-related impulse responses & transfer functions of rabbit

Sound localization cues * interaural time difference (ITD) 5 μsec; ~ 1 deg azimuth. * interaural level difference (ILD) * spectral cues * direct/reverberant energy ratio; distance virtual auditory space

cortex the ascending auditory pathways of the cat thalamus midbrain binaural & monaural pathways CN & SOC pons Brodal, 1981

Brodal Fig 9 -8 mso: medial sup. olive; lso: lateral sup. olive ntb: nuc. trazepoid body; ic: inf. coll.

cat superior olivary complex LSO MSO MNTB D MNTB M (somata & dendrites) (axons & endings) Tsuchitani, 1978, Fig. 10

ILD processing in LSO Purves Fig 13 -14 A

Purves Fig 13 -14 B ILD processing in LSO

model for ITD coding employing neural delay lines & coincidence detectors MSO neurons act as coincidence detectors. maximum firing when left (acoustic delay + neural delay) = right (acoustic delay + neural delay) Jeffress, 1948; Kuwada best ITD 1 = 0 ms; sound in front best ITD 2 = 50 ms best ITD 3 = 100 ms. . . best ITD 7 = 700 ms; sound on opposite side

Kim, Bishop, Kuwada, 2010 head-related impulse responses & transfer functions of rabbit

Inferior colliculus neurons show azimuth tuning. 10 d. B 30 d. B 50 d. B Kuwada, Bishop, Alex, Condit, Kim, 2011, J. Neurophys.

auditory & somatosen. inputs Purves Box 20 B Sup. coll. contains visual and auditory space maps.

cortex the descending auditory pathways of the cat thalamus midbrain CN & SOC pons Brodal, 1981

olivocochlear neurons LOC: lateral olivocochlear MOC: medial olivocochlear Warr et al. , 2002

inner hair cell outer hair cell afferent nerve ending * * efferent nerve ending efferent nerve fibers Smith, 1975 afferent nerve fibers