Auditory Neuroscience 1 Spatial Hearing. Systems Biology Doctoral Training Program Physiology course Prof. Jan Schnupp [email protected] HowYourBrainWorks.net. Hearing: an impossible task!. http://auditoryneuroscience.com/foxInSnow. ITD. Interaural Time Difference (ITD) Cues.
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ITDs are powerful cues to sound source direction, but they are ambiguous (“cones of confusion”)
Unlike ITDs, ILDs are highly frequency dependent. At higher sound frequencies ILDs tend to become larger, more complex, and hence potentially more informative.
ILD at 700 Hz
ILD at 11000 Hz
Hofman et al. made human volunteers localize sounds in the dark, then introduced plastic molds to change the shape of the concha. This disrupted spectral cues and led to poor localization, particularly in elevation.
Over a prolonged period of wearing the molds, (up to 3 weeks) localization accuracy improved.
ITD tuning varies with sound frequency: no map?
CN, cochlear nuclei;
SOC, superior olivary complex; NLL, nuclei of the lateral lemniscus; IC, inferior colliculus; MGB, medial geniculate body.
Jenkins & Merzenich, J. Neurophysiol, 1984
Linear Prediction of Responses
r(t) = i1(t-1) w1(1) + i1(t-2) w1(2)+ ...+ i2(t-1) w2(1) + i2(t-2) w2(2)+ ...
+ i3(t-1) w3(1) + i2(t-2) w3(2)+ ...
Left and Right Ear Frequency-Time Response Fields
Virtual Acoustic Space Stimuli
Schnupp et al Nature 2001
Vowel type (timbre) Cortex?
Pitch (Hz)Responses to Artificial Vowels in Space