Controversies on the caloric response. From Bárány's theory to studies in microgravity

Two objections against Robert Bárány's scientific contributions are reviewed. Firstly the Medical Faculty in Vienna raised the question as to whether Bárány really could be credited with the initial discovery of the caloric reaction in man and whether therefore it was justified to have awarded him the Nobel Prize in 1914. The second objection consists in strong doubt as to the correctness of Bárány's theory that changes in the temperature of the irrigation water result in density changes in the endolymph, permitting the fluid to be acted upon by gravity, yielding convection currents. Four arguments against Bárány's theory have been put forward: that (1) a caloric response can be elicited from "dead" ears, (2) the two points of reversal of the caloric response from right- to left-beating do not lie 180 degrees apart, (3) the duration of the caloric response, to both cold and warm stimuli, is greater in the face-up than in the face-down position, and (4) caloric nystagmus can also be evoked in a weightless environment. Conclusions based on results of caloric tests in microgravity have been criticised. It is not possible today to dismiss Bárány's theory as incorrect on scientific grounds. On the contrary, there is evidence for the occurrence of both thermal convective currents and a simultaneous non-convective thermal mechanism, acting together in the caloric response.