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1. The relation between discharge frequency and angular head position was determined for a population of regularly discharging single first-order vestibular neurones in the eighth nerve of the barbiturate anaesthetized cat.
2. Each axon had a characteristic head position which was maximally excitatory to it, and a diametrically opposed head position which was minimally excitatory.
3. After correction for phase shifts introduced by the orientation of preferred excitability, discharge rate in statoreceptor afferents varied as a power function of the sine of angular head position with exponents ranging from 0·9 to 1·6.
4. Experimentally determined discharge rates were compared with the predictions of a computer simulation model incorporating the idea that shearing force acting on morphologically polarized receptors is the adequate stimulus for macular receptor cells.
5. This approach permitted the identification of a population of first-order vestibular afferents whose discharge frequency varied with head position as did the magnitude of shear force computed for individual receptors, each most excited in a particular head position.
6. The majority of the spatial orientations of maximal sensitivity defined a surface which is tilted by approximately 30° with reference to the HorsleyClarke horizontal plane, implying that most statoreceptor afferents are maximally sensitive to position changes when the cat's head is at or near its normal position.
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