Tonotopic map: how frequency coding is maintained along the auditory pathway.

Tonotopic map: how frequency coding is maintained along the auditory pathway.

• A. The map is lost after the cochlea and reconstructed by the primary auditory cortex.
• B. The frequency map is generated anew in the auditory cortex.
• C. The map is preserved from base to apex of the cochlea through successive relay nuclei in the brainstem and thalamus.
• D. Tonotopy is not preserved beyond the cochlea.

Answer: (C)

Tonotopy is the orderly spatial arrangement of frequency that starts in the cochlea and is carried upward through the auditory pathway. The base of the cochlea responds best to high frequencies, while the apex responds best to low frequencies, creating a frequency map along the basilar membrane. This spatial organization is preserved as the signal travels through successive relay stations in the brainstem and then through the thalamus to the auditory cortex. At each relay, neurons tuned to neighboring frequencies remain adjacent in the next structure, so the base-to-apex frequency arrangement is carried along rather than being rebuilt or lost. That’s why the correct idea is that the map is preserved through these successive relay nuclei.

Tonotopy is the orderly spatial arrangement of frequency that starts in the cochlea and is carried upward through the auditory pathway. The base of the cochlea responds best to high frequencies, while the apex responds best to low frequencies, creating a frequency map along the basilar membrane. This spatial organization is preserved as the signal travels through successive relay stations in the brainstem and then through the thalamus to the auditory cortex. At each relay, neurons tuned to neighboring frequencies remain adjacent in the next structure, so the base-to-apex frequency arrangement is carried along rather than being rebuilt or lost. That’s why the correct idea is that the map is preserved through these successive relay nuclei.