How do auditory neurons respond differently to pure tones and frequency-modulated sounds?

In the hierarchical organization of the auditory system, neurons exhibit increasing complexity in their stimulus requirements as information moves from the periphery to higher brain centers.1

• Peripheral Neurons: These neurons typically respond well to pure tones. In the cochlea, the frequency of a pure tone is encoded by the specific location of activated neurons along the basilar membrane, a process known as place theory.123
• Central Neurons: As auditory input reaches higher processing areas, such as the auditory cortex, neurons become sensitive to more complex acoustic features. While some neurons remain tuned to specific frequencies, others are specialized to respond to dynamic changes in sound. Specifically, certain central neurons do not respond to constant-frequency notes but are activated by frequency-modulated sounds—those where the frequency rises or falls. These neurons may also be sensitive to the rate of frequency change, which helps the brain interpret information such as whether the distance from a sound source is increasing or decreasing.13