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Interaural time differences localize sound sources in the horizontal plane. A. When a sound, such as a pure tone, arises from the right, the right ear detects
the sound earlier than the left ear. The difference in the time of arrival at the two ears is the interaural time delay (ITD). Cochlear nerve fibers and their
bushy cell targets fire in phase with changes in sound pressure. Although individual neurons sometimes skip cycles, the population of bushy cells encodes
the timing of low-frequency sounds and its frequency with every cycle. Comparison of the timing of action potentials of bushy cells at the two sides reveals
the ITDs (slanted black lines).
B. InterauralSource:
time differences
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be detected
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delay lines.
If axons
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The Auditory
Nervous
Principles
of Neural
Fifth Editon
terminals before they reach the farthest ones. An array of neurons that detects coincident inputs from delay lines can produce a map of ITDs. When
Citation: Kandel ER, Schwartz JH, Jessell TM, Siegelbaum SA, Hudspeth AJ, Mack S. Principles of Neural Science, Fifth Editon; 2012 Available
sounds come from the right, action potentials from the right ear must be delayed to compensate for the fact that they arrive earlier than those from the left
at: http://mhmedical.com/ Accessed: May 02, 2017
and to allow the signals from right and left to coincide at one side of the array (mustard-colored cell). Such an arrangement of delay lines has been found
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in the nucleus laminaris of the barn owl, the homolog of the medial superior olivary nucleus.