Hypothesis: The aim of this study was to investigate the possibility of afferent subcortical components related to static pressure changes of the human middle ear.
Background: The normal middle ear function depends on a proper regulation of middle ear pressure, whereas an inadequate regulation with negative pressures is considered a major pathogenetic factor responsible for a variety of middle ear disorders. However, although studies on middle ear pressure and related clinical problems are common, studies on the role of its central control have been remarkably few. Hence, we attempted recording evoked brain potentials in response to static pressure stimulation of the middle ear in normal adult humans.
Methods: The experiments were conducted by stimulating the middle ear in 6 subjects with a novel computer-controlled static pressure triggering system for rapid synchronized pressure loads of +3 kPa. The resulting brain evoked responses were recorded from 64 surface electrodes using a standard electroencephalogram cap. A wide-band electroencephalogram acquisition method was adopted, signals were sampled at 20,000 Hz, and band-pass filtered between 150 and 3,000 Hz.
Results: Repeatable pressure evoked brain potentials and topographies were described for the first time. Hence, source localization could be adopted on a realistic head model, which showed the location of these early neural generators in the brainstem, followed by activity generated by the cerebellum.
Conclusion: The findings are in agreement with previous animal experiments and provide basic information for further investigations on central components related to static pressure changes of the human middle ear.