Live cochleas are much more sharply tuned than cadaver measurements suggested

Evidence

Von Békésy’s studies used cadaver cochlea and high-level stimuli. As a result, he measured passive responses, reflecting purely mechanical properties of the BM. His measurements demonstrated broad tuning: a large portion of the BM was activated by a single sound. Modern in vivo measurements illustrate a much more narrowly tuned traveling wave, in that a pure tone vibrates many fewer basilar membrane locations (Narayan, Temchin, Recio, & Ruggero, 1998; Rhode, 1971; Sellick, Patuzzi, & Johnstone, 1982). Thus, in vivo, the cochlea provides a more frequency-specific representation than originally thought. Although von Békésy was unable to measure BM responses to a variety of stimulus levels, measurements down to levels of 10 dB SPL indicate that cochlear tuning is much sharper at low versus high levels (Robles, Ruggero, & Rich, 1986). — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 227

Modern in vivo measurements illustrate a much more narrowly tuned traveling wave, in that a pure tone vibrates many fewer basilar membrane locations (Narayan, Temchin, Recio, & Ruggero, 1998; Rhode, 1971; Sellick, Patuzzi, & Johnstone, 1982). Thus, in vivo, the cochlea provides a more frequency-specific representation than originally thought. Although von Békésy was unable to measure BM responses to a variety of stimulus levels, measurements down to levels of 10 dB SPL indicate that cochlear tuning is much sharper at low versus high levels (Robles, Ruggero, & Rich, 1986). — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 227

Categorization

• QUESTION: What mechanism (outer hair cell motility?) explains why tuning sharpens at low levels? The text teases this and 228 answers it.
• XREF: Connects to the widely-taught von Békésy passive traveling-wave picture; the corrective here adds an important caveat to any textbook treatment of cochlear mechanics. — connects to: Measurement method changes how broad auditory tuning appears.; Von Békésy’s tuning curves were broadened by post-mortem cochlear damage.
• corroborated: 3 independent passages support this claim — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 227

Broader Connections

• Measurement method changes how broad auditory tuning appears. #expands (0.85)