Abstract

Background: The caloric test is a generally accepted method of assessing the peripheral vestibular system. Several mechanisms of action have been postulated to account for the nystagmic response observed.

Objective: We investigated the possibility of a novel contributing mechanism relating to change in the relative specific gravity of the cupula.

Methods: Five cupulae were harvested from fresh wood pigeons, and immersed in water baths at 21°C, 41°C, 51°C, 60°C and 80°C for 5 minutes. Changes in cupular buoyancy at different temperatures were recorded.

Results: Between 21°C and 51°C all cupulae were seen to sink. At 60°C the cupulae consistently rose.

Conclusions: These observations suggest the presence of an alternative mechanism for the caloric effect involving changing cupular specific gravity with temperature.