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

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

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

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

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

intracellular recording 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.

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

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

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

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

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

ILD processing in LSO Purves Fig 13-14A

ILD processing in LSO Purves Fig 13-14B

model for ITD coding employing neural delay lines & coincidence detectors MSO neurons act as coincidence detectors. 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 maximum firing when left (acoustic delay + neural delay) = right (acoustic delay + neural delay) Jeffress, 1948; Kuwada

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

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

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

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

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

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