What principle explains how the basilar membrane encodes different frequencies along its length?

What principle explains how the basilar membrane encodes different frequencies along its length?

• A. Tonotopy.
• B. Frequency coding.
• C. Loudness mapping.
• D. Temporal coding.

Answer: (A)

Tonotopy is the idea that frequency is represented along the length of the basilar membrane. The base of the membrane is stiff and narrow, while toward the apex it becomes wider and more flexible. When a sound occurs, different frequencies cause the membrane to maximize its vibration at different locations: high frequencies peak at the stiff base, low frequencies peak nearer the flexible apex. Hair cells at those locations respond most strongly, sending frequency-specific signals via auditory nerve fibers to the brain. This spatial organization is maintained through the auditory pathways, creating a map of frequency along the cochlea and beyond. While other concepts describe how neurons code frequency, they don’t capture why the basilar membrane shows a length-dependent frequency response. Frequency coding refers to how firing rate or timing represents pitch, loudness mapping to amplitude, and temporal coding to timing patterns—none of these explain the place-based mapping along the membrane itself.

Tonotopy is the idea that frequency is represented along the length of the basilar membrane. The base of the membrane is stiff and narrow, while toward the apex it becomes wider and more flexible. When a sound occurs, different frequencies cause the membrane to maximize its vibration at different locations: high frequencies peak at the stiff base, low frequencies peak nearer the flexible apex. Hair cells at those locations respond most strongly, sending frequency-specific signals via auditory nerve fibers to the brain. This spatial organization is maintained through the auditory pathways, creating a map of frequency along the cochlea and beyond.

While other concepts describe how neurons code frequency, they don’t capture why the basilar membrane shows a length-dependent frequency response. Frequency coding refers to how firing rate or timing represents pitch, loudness mapping to amplitude, and temporal coding to timing patterns—none of these explain the place-based mapping along the membrane itself.