PHGY 314 Lecture Notes - Lecture 16: Hearing Aid, Ototoxicity, Eustachian Tube
31 Oct 2016
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Hair cells (cid:1) afferents (cid:1) cochlear nucleus (cid:1) superior olivary nucleus/complex (cid:1) inferior colliculus (contralateral at this point)(cid:1) medial geniculate nucleus (cid:1) auditory cortex a1. Cues for sound localization: figuring out where sound comes from. Azimuth = direction straight ahead: difference in arrival time: interaural time differences (itd) @mso, vsound = 350m/s, sound reaches ear nearer to source first, in humans, 1ms difference btwn reaching near ear to far ear. Intensity difference: interaural level differences (ild) @lso pathway due to inevitable jitter: head casts a shadow on sound, dampening sound from near to farther ear. Ild depends on frequency: 2:1 @1000hz, 100:1 @10000hz, so used for f > 3000hz, lso: lateral superior olive, each neuron is sensitive to different ild. So there"s a 1500-3000hz window where sound localization is difficult to resolve! A1 auditory cortex aka brodmann"s areas 41/42 aka heschl"s gyrus: Ice cube model of columns: tonotopic map sectioning 20khz, neocortex layers, frequency is high @ rostral, low @caudal.
