Background & aims: Cerebral evoked potential (EP) responses to visceral stimulation represent a powerful method to assess visceral afferent pathways. The aim of this study was to establish basic stimulation parameters (dose-response relationship in EP amplitude and topographic brain organization) during electrical esophageal stimulation.
Methods: Electrical esophageal stimulation was performed in repeated series of 24 stimuli in 15 healthy subjects (25 years) by steps of 5 mA, ranging from 0.5 mA (sham) to 25 mA. EPs were obtained using scalp electrodes positioned according to the 10/20 International electroencephalographic system. Topographic EP maps were created using interpolation techniques.
Results: No cerebral responses were recorded with sham stimulation. A significant intensity-dependent increase of the major EP peaks (N1-P2) was observed between 5 and 25 mA (P < 0.05). A significant shortening of the mean peak latency of the first peak (N1) occurred with increasing stimulus intensity (P < 0.0001). Topographic brain maps localized the early EP peaks centrally, whereas later peaks were spread symmetrically over the centroparietal region.
Conclusions: The clear dose-response relationship in the brain response with increasing stimulus intensities probably reflects increased recruitment of afferent fibers. Early peaks originate from deep central brain structures, whereas later peaks are localized exclusively in cortical regions.