Role of the "PLACE" and "VOLLEY" Principle in determination of sound frequency
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"PLACE principle" "VOLLEY principle" sound frequency
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https://www.ncbi.nlm.nih.gov/books/NBK11105
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Sound frequency is perceived mainly by two complementary mechanisms:
| Principle | What is coded | Main frequency range | Basis |
|---|---|---|---|
| Place principle | Where the basilar membrane vibrates maximally | Mainly intermediate and high frequencies | Tonotopic organization of cochlea |
| Volley principle | Timing of auditory-nerve impulses | Low and intermediate frequencies | Phase-locked neural firing |
1. Place principle
A sound produces a traveling wave on the basilar membrane. Its frequency determines the point of maximum vibration:
- High-frequency sounds vibrate maximally near the base of the cochlea, close to the oval window.
- Low-frequency sounds vibrate maximally near the apex, near the helicotrema.
- Intermediate frequencies stimulate intermediate positions.
Hair cells at that location activate their corresponding auditory-nerve fibers. This orderly frequency map, called tonotopy, is maintained from the cochlea through auditory pathways to the auditory cortex.
Thus, the brain identifies frequency from the place of maximal activation. Guyton describes it as the major mechanism for determining sound frequency. Guyton and Hall Textbook of Medical Physiology, p. 660.
2. Volley principle
The place mechanism distinguishes low tones poorly, especially below roughly 200 Hz, because very low frequencies produce maximal vibration near the same apical region.
For these frequencies, auditory-nerve fibers fire in synchrony with a particular phase of the sound wave. This is phase locking.
- A single neuron cannot fire on every cycle when the frequency is high because of its refractory period.
- Instead, different neurons fire on different cycles, but each remains phase-locked to the sound.
- Their combined or pooled discharge pattern forms a volley, whose repetition rate represents the sound frequency.
So, the brain can infer pitch from the temporal pattern of impulses, not just their cochlear location.
Guyton gives an approximate effective range of 20 to 1500-2000 Hz for volley coding. Guyton and Hall Textbook of Medical Physiology, p. 660. Other neuroscience texts describe phase locking up to about 5 kHz, though it progressively becomes less reliable at higher frequencies; above this, tonotopic place coding predominates. Neuroscience: Exploring the Brain, 5th ed., pp. 1072-1074.
In one line
- Place principle: “Which part of the cochlea is activated?”
- Volley principle: “How often, in synchrony with the waveform, does the auditory-nerve population fire?”
They work together: temporal/volley cues are most helpful for low frequencies, both contribute at intermediate frequencies, and place coding dominates at high frequencies. This combined coding is consistent with contemporary auditory-neuroscience literature on tonotopic place coding.
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